runtime: use SwissTable #54766

zhangyunhao116 · 2022-08-30T06:49:13Z

Abstract

From ByteDance Programming Language Team

We suggest using SwissTable in the runtime to replace the original implementation of the hashmap.

SwissTable is now used in abseil and rust by default. We borrowed ideas from the two implementations and combined some optimization ideas of Go's original hashmap to construct the current implementation.

See the following comment for performance comparison(the GitHub issue has a character limit).

Motivations

We need to improve the performance of the hashmap as much as possible. At ByteDance, our Go service consumes about 4% of the CPU on hashmap. It is worth noting that on many services, the CPU consumption of mapassign and mapaccess are almost 1:1, so the improvement of insertion performance is equally important.
Support dynamic adjustment of the capacity of the hashmap. Some Go services will make a map too large due to burst traffic, which will cause a lot of pressure on the memory, but the map does not shrink after elements removal. We found that there are also many related discussions in the community:

Implementations

Basic version: https://go-review.googlesource.com/c/go/+/426614
SIMD version: TODO

Tasks

Basic version: without SIMD, follow the original memory layout.
Add SIMD support for x86: WIP, in the following CL.
Aggregates all tophash into an array: In the plan, it requires more performance comparison data.
Support hashmap resizing: More discussion is needed.
Set bucketCnt to 4 on 32-bit platforms: More discussion is needed.

Advantages compared to the original implementation

The overall performance is better, and we can also use SIMD to improve performance.
SwissTable's LoadFactor can be set higher to save some memory.
Open-addressing and making dynamic adjustments to the capacity is easier to implement.
After allocating a fixed-size hashmap, if the number of inserted elements does not exceed the capacity, no additional memory is required, and the performance will be significantly improved, which has a greater advantage over reused fixed-size hashmap. (The original hashmap may still allocate additional memory even when the limit is not exceeded)

Disadvantages compared to the original implementation

The rehash is done at once, so
- Some services that are sensitive to latency may experience performance degradation. (but we do not observe this for now)
- In some cases, when the hashmap needs to grow, it may consume more CPU than the original implementation. (The previous implementation uses incremental rehash)
Since SwissTable needs to ensure that each bucket has at least one empty slot, it will cause performance degradation in some cases. For example, if we insert an element when there are seven elements in the hashmap, the CPU consumption will significantly increase because the hashmap needs to grow.

Implementation details

Here is an overview of the basic version. For more detailed implementation, you can read the code. Before reading the code, it is recommended to check the video or the article in the references to get a general idea of how it works.

Differences with SwissTable

Move tophash into the bucket, not as an array alone.

The classic SwissTable aggregates all tophash into an array (also called control bytes array, here we follow the convention, called tophash), while the original hashmap of Go puts tophash and items in the same bucket.

Our experiments outside the runtime found that if tophash is used as an array alone, we couldn’t find any performance wins. This is probably because we need two memory allocations when initializing the hashmap.

So we use the bucket memory layout almost the same as the original in the current version. In the future, we may consider aggregating all tophash into an array, using a data structure similar to sync.Pool, so that all tophash of the hashmap can be reused to improve performance.

Due to this change, when we delete a key/value, we only need to determine whether the current bucket still has empty slots, because the location where we access the bucket is relatively fixed, unlike the classic implementation, which can be accessed from different addresses.

Differences with the original implementation

For hashmap header (hmap) and hiter

Removed fields about overflow and incremental rehash.

For bucket (bmap)

The tophash is still 8-bit(uint8), but 7-bit for hash info and 1-bit as flags.
Removed overflow pointer.

For the way of querying

The query process changes from querying the overflow pointer to finding the next bucket (using triangular probing) until the first empty slot is found. SwissTable theoretically guarantees that there is at least one empty slot.

For initializing bucket arrays

The initial state of the tophash is 0xff instead of 0; 0xff represents the empty slot now.

References

The text was updated successfully, but these errors were encountered:

zhangyunhao116 · 2022-08-30T06:49:22Z

Performance comparison

Here the SwissTable is just a basic version. To avoid a CL bringing too many changes, it does not use SIMD and is compatible with the previous hashmap memory layout(it means many optimizations are not included in this version). Its performance still has room for improvement; we will add these optimizations in subsequent CLs.

In general, the performance changes for the basic version of SwissTable are as follows.

There is a significant improvement (20% ~ 50%) when querying a large hashmap or querying an element that does not exist in the hashmap. When querying a hashmap with fewer elements, performance degradation is up to 20%.
Insertions and deletions have been significantly improved in almost all cases (20% ~ 50%).
The performance of iterate is improved by about 10%.
Memory usage is reduced by 0% ~ 25% in most cases. Reusing a fixed-size hashmap no longer consumes any extra memory.
Since the growth is done at once, the CPU usage is significantly reduced in the case of continuous growth, but in some cases, the CPU consumption may also increase significantly.

Platform

GO: linux/amd64
CPU: AMD 3700x(8C16T)
OS: Ubuntu 22.04.1 LTS (GNU/Linux 5.15.0-43-generic x86_64)
MEMORY: 16G x 2 (DDR4 3200MHz)

Benchmark-1

Located in https://github.com/zhangyunhao116/gomapbench

This benchmark contains performance comparisons of common operations of common types in different situations.

INFO

name                                   old time/op    new time/op    delta
MapIter/Int/6-16                         60.2ns ± 1%    55.7ns ± 0%    -7.35%  (p=0.000 n=9+7)
MapIter/Int/12-16                         121ns ±10%     102ns ± 3%   -15.51%  (p=0.000 n=10+10)
MapIter/Int/18-16                         173ns ± 2%     165ns ± 1%    -4.58%  (p=0.000 n=10+8)
MapIter/Int/24-16                         214ns ± 4%     194ns ± 3%    -9.46%  (p=0.000 n=10+10)
MapIter/Int/30-16                         287ns ± 3%     272ns ± 2%    -5.22%  (p=0.000 n=10+9)
MapIter/Int/64-16                         609ns ± 0%     572ns ± 3%    -6.10%  (p=0.000 n=7+10)
MapIter/Int/128-16                       1.21µs ± 4%    1.17µs ± 2%    -3.63%  (p=0.004 n=10+10)
MapIter/Int/256-16                       2.46µs ± 2%    2.23µs ± 2%    -9.31%  (p=0.000 n=10+10)
MapIter/Int/512-16                       4.98µs ± 4%    4.38µs ± 2%   -12.22%  (p=0.000 n=10+10)
MapIter/Int/1024-16                      9.94µs ± 3%    8.84µs ± 2%   -11.11%  (p=0.000 n=10+10)
MapIter/Int/2048-16                      20.1µs ± 3%    17.8µs ± 1%   -11.33%  (p=0.000 n=10+10)
MapIter/Int/4096-16                      39.7µs ± 1%    35.5µs ± 2%   -10.49%  (p=0.000 n=10+10)
MapIter/Int/8192-16                      79.3µs ± 2%    71.8µs ± 1%    -9.42%  (p=0.000 n=10+10)
MapIter/Int/65536-16                      631µs ± 2%     571µs ± 1%    -9.52%  (p=0.000 n=10+9)
MapAccessHit/Int64/6-16                  4.24ns ± 1%    3.71ns ± 1%   -12.37%  (p=0.000 n=8+9)
MapAccessHit/Int64/12-16                 6.61ns ± 6%    6.63ns ±11%      ~     (p=0.796 n=9+9)
MapAccessHit/Int64/18-16                 6.74ns ± 4%    7.01ns ± 1%    +4.02%  (p=0.002 n=9+8)
MapAccessHit/Int64/24-16                 7.81ns ± 8%    8.17ns ± 5%    +4.62%  (p=0.034 n=10+8)
MapAccessHit/Int64/30-16                 6.23ns ± 6%    6.99ns ± 1%   +12.34%  (p=0.000 n=10+7)
MapAccessHit/Int64/64-16                 6.68ns ± 6%    7.22ns ± 2%    +8.08%  (p=0.000 n=10+9)
MapAccessHit/Int64/128-16                6.98ns ± 6%    7.32ns ± 6%    +4.93%  (p=0.004 n=10+10)
MapAccessHit/Int64/256-16                7.12ns ± 2%    7.28ns ± 2%    +2.21%  (p=0.002 n=9+10)
MapAccessHit/Int64/512-16                7.68ns ± 4%    7.40ns ± 2%    -3.65%  (p=0.000 n=9+10)
MapAccessHit/Int64/1024-16               8.85ns ± 2%    7.35ns ± 2%   -16.92%  (p=0.000 n=10+9)
MapAccessHit/Int64/2048-16               11.2ns ± 3%     7.7ns ± 1%   -31.23%  (p=0.000 n=10+8)
MapAccessHit/Int64/4096-16               14.1ns ± 1%     7.9ns ± 1%   -43.96%  (p=0.000 n=7+8)
MapAccessHit/Int64/8192-16               16.2ns ± 2%     8.2ns ± 2%   -49.14%  (p=0.000 n=10+10)
MapAccessHit/Int64/65536-16              19.6ns ± 2%    10.5ns ± 1%   -46.18%  (p=0.000 n=10+9)
MapAccessHit/Int32/6-16                  3.78ns ± 1%    3.86ns ± 1%    +2.12%  (p=0.000 n=10+8)
MapAccessHit/Int32/12-16                 6.23ns ± 6%    6.16ns ± 4%      ~     (p=0.483 n=10+9)
MapAccessHit/Int32/18-16                 6.42ns ± 5%    6.99ns ± 3%    +8.91%  (p=0.000 n=10+9)
MapAccessHit/Int32/24-16                 7.46ns ± 5%    8.60ns ± 8%   +15.32%  (p=0.000 n=9+10)
MapAccessHit/Int32/30-16                 6.07ns ± 5%    6.97ns ± 1%   +14.88%  (p=0.000 n=10+8)
MapAccessHit/Int32/64-16                 6.50ns ± 4%    7.18ns ± 5%   +10.34%  (p=0.000 n=9+10)
MapAccessHit/Int32/128-16                6.68ns ± 6%    7.15ns ± 4%    +7.12%  (p=0.000 n=10+10)
MapAccessHit/Int32/256-16                6.81ns ± 4%    7.32ns ± 4%    +7.45%  (p=0.000 n=10+10)
MapAccessHit/Int32/512-16                7.40ns ± 3%    7.30ns ± 3%      ~     (p=0.156 n=9+10)
MapAccessHit/Int32/1024-16               8.46ns ± 2%    7.38ns ± 1%   -12.79%  (p=0.000 n=10+9)
MapAccessHit/Int32/2048-16               11.0ns ± 3%     7.6ns ± 2%   -31.46%  (p=0.000 n=10+10)
MapAccessHit/Int32/4096-16               13.9ns ± 2%     7.8ns ± 2%   -44.12%  (p=0.000 n=10+10)
MapAccessHit/Int32/8192-16               15.8ns ± 2%     8.1ns ± 1%   -48.99%  (p=0.000 n=10+10)
MapAccessHit/Int32/65536-16              19.0ns ± 2%    10.3ns ± 2%   -45.85%  (p=0.000 n=10+10)
MapAccessHit/Str/6-16                    13.5ns ± 1%    12.7ns ± 2%    -5.88%  (p=0.000 n=9+10)
MapAccessHit/Str/12-16                   9.77ns ±11%    9.40ns ± 2%      ~     (p=0.460 n=10+8)
MapAccessHit/Str/18-16                   9.05ns ± 7%    9.47ns ± 1%    +4.66%  (p=0.001 n=9+9)
MapAccessHit/Str/24-16                   9.92ns ± 7%   10.07ns ± 9%      ~     (p=0.604 n=9+10)
MapAccessHit/Str/30-16                   8.46ns ± 7%    9.43ns ± 1%   +11.50%  (p=0.000 n=10+8)
MapAccessHit/Str/64-16                   8.91ns ± 5%    9.57ns ± 2%    +7.39%  (p=0.000 n=10+8)
MapAccessHit/Str/128-16                  9.82ns ± 4%   10.58ns ± 5%    +7.75%  (p=0.000 n=10+10)
MapAccessHit/Str/256-16                  11.8ns ± 4%    11.4ns ± 1%    -3.01%  (p=0.008 n=10+8)
MapAccessHit/Str/512-16                  14.6ns ± 2%    11.9ns ± 2%   -18.89%  (p=0.000 n=8+9)
MapAccessHit/Str/1024-16                 17.9ns ± 2%    12.7ns ± 1%   -29.02%  (p=0.000 n=10+9)
MapAccessHit/Str/2048-16                 21.5ns ± 3%    13.0ns ± 2%   -39.43%  (p=0.000 n=10+9)
MapAccessHit/Str/4096-16                 25.1ns ± 1%    13.2ns ± 2%   -47.63%  (p=0.000 n=10+10)
MapAccessHit/Str/8192-16                 26.6ns ± 1%    14.2ns ± 1%   -46.62%  (p=0.000 n=9+9)
MapAccessHit/Str/65536-16                31.8ns ± 1%    17.3ns ± 2%   -45.64%  (p=0.000 n=10+10)
MapAccessMiss/Int64/6-16                 8.03ns ± 1%    7.35ns ± 1%    -8.39%  (p=0.000 n=10+10)
MapAccessMiss/Int64/12-16                10.2ns ± 2%    18.3ns ± 3%   +79.48%  (p=0.000 n=8+8)
MapAccessMiss/Int64/18-16                10.3ns ± 1%     7.2ns ± 1%   -29.85%  (p=0.000 n=9+8)
MapAccessMiss/Int64/24-16                13.9ns ± 2%    10.8ns ± 2%   -22.43%  (p=0.000 n=7+8)
MapAccessMiss/Int64/30-16                10.1ns ± 3%     7.1ns ± 3%   -29.69%  (p=0.000 n=8+8)
MapAccessMiss/Int64/64-16                10.3ns ± 1%     7.9ns ±12%   -23.29%  (p=0.000 n=7+10)
MapAccessMiss/Int64/128-16               10.2ns ± 2%     7.6ns ± 8%   -25.64%  (p=0.000 n=10+9)
MapAccessMiss/Int64/256-16               10.4ns ± 2%     7.9ns ± 7%   -23.40%  (p=0.000 n=9+9)
MapAccessMiss/Int64/512-16               10.3ns ± 3%     7.9ns ± 8%   -23.37%  (p=0.000 n=9+10)
MapAccessMiss/Int64/1024-16              10.4ns ± 2%     8.0ns ± 4%   -22.40%  (p=0.000 n=9+10)
MapAccessMiss/Int64/2048-16              10.4ns ± 2%     7.9ns ± 3%   -23.97%  (p=0.000 n=10+10)
MapAccessMiss/Int64/4096-16              10.4ns ± 2%     8.2ns ± 3%   -21.67%  (p=0.000 n=10+10)
MapAccessMiss/Int64/8192-16              10.3ns ± 2%     8.6ns ± 3%   -16.95%  (p=0.000 n=10+10)
MapAccessMiss/Int64/65536-16             13.5ns ± 2%    10.9ns ± 3%   -19.23%  (p=0.000 n=9+8)
MapAccessMiss/Int32/6-16                 6.17ns ± 2%    7.45ns ± 2%   +20.86%  (p=0.000 n=10+10)
MapAccessMiss/Int32/12-16                8.50ns ± 1%   15.94ns ± 3%   +87.44%  (p=0.000 n=8+8)
MapAccessMiss/Int32/18-16                8.49ns ± 2%    8.21ns ±30%      ~     (p=0.156 n=9+10)
MapAccessMiss/Int32/24-16                11.9ns ± 2%    10.8ns ± 2%    -9.03%  (p=0.000 n=8+7)
MapAccessMiss/Int32/30-16                8.48ns ± 1%    7.53ns ±15%      ~     (p=0.138 n=10+10)
MapAccessMiss/Int32/64-16                8.49ns ± 1%    8.11ns ±17%    -4.50%  (p=0.034 n=8+10)
MapAccessMiss/Int32/128-16               8.89ns ± 2%    7.86ns ±10%   -11.57%  (p=0.000 n=7+10)
MapAccessMiss/Int32/256-16               8.72ns ± 3%    7.83ns ± 3%   -10.23%  (p=0.000 n=10+9)
MapAccessMiss/Int32/512-16               8.79ns ± 4%    7.70ns ± 4%   -12.40%  (p=0.000 n=10+9)
MapAccessMiss/Int32/1024-16              8.81ns ± 1%    7.74ns ± 5%   -12.10%  (p=0.000 n=9+10)
MapAccessMiss/Int32/2048-16              9.16ns ± 1%    7.91ns ± 2%   -13.64%  (p=0.000 n=7+9)
MapAccessMiss/Int32/4096-16              9.40ns ± 2%    8.15ns ± 3%   -13.29%  (p=0.000 n=9+9)
MapAccessMiss/Int32/8192-16              9.47ns ± 2%    8.29ns ± 2%   -12.45%  (p=0.000 n=9+9)
MapAccessMiss/Int32/65536-16             12.9ns ± 2%    10.6ns ± 2%   -18.32%  (p=0.000 n=8+10)
MapAccessMiss/Str/6-16                   5.69ns ± 1%    6.89ns ± 1%   +21.05%  (p=0.000 n=10+9)
MapAccessMiss/Str/12-16                  11.7ns ± 5%    10.6ns ±11%    -9.74%  (p=0.001 n=10+10)
MapAccessMiss/Str/18-16                  10.2ns ± 1%     9.6ns ± 1%    -5.81%  (p=0.000 n=8+8)
MapAccessMiss/Str/24-16                  12.5ns ±11%    11.4ns ± 9%    -8.83%  (p=0.011 n=10+10)
MapAccessMiss/Str/30-16                  10.8ns ± 4%     8.9ns ± 1%   -17.66%  (p=0.000 n=10+8)
MapAccessMiss/Str/64-16                  10.8ns ± 4%     9.3ns ± 8%   -13.63%  (p=0.000 n=10+10)
MapAccessMiss/Str/128-16                 12.0ns ± 7%     9.9ns ±10%   -17.57%  (p=0.000 n=10+10)
MapAccessMiss/Str/256-16                 11.2ns ± 3%    10.0ns ± 5%   -11.09%  (p=0.000 n=10+10)
MapAccessMiss/Str/512-16                 11.1ns ± 3%     9.6ns ± 6%   -13.51%  (p=0.000 n=10+10)
MapAccessMiss/Str/1024-16                12.3ns ± 2%     9.7ns ± 3%   -20.85%  (p=0.000 n=10+10)
MapAccessMiss/Str/2048-16                15.7ns ± 2%    10.1ns ± 4%   -35.32%  (p=0.000 n=10+10)
MapAccessMiss/Str/4096-16                14.0ns ± 3%    10.2ns ± 3%   -27.20%  (p=0.000 n=10+10)
MapAccessMiss/Str/8192-16                14.1ns ± 2%    10.9ns ± 4%   -22.70%  (p=0.000 n=10+10)
MapAccessMiss/Str/65536-16               19.2ns ± 2%    13.6ns ± 4%   -29.47%  (p=0.000 n=10+10)
MapAssignGrow/Int64/6-16                 69.1ns ± 1%    69.5ns ± 1%      ~     (p=0.133 n=9+10)
MapAssignGrow/Int64/12-16                 759ns ± 0%     539ns ± 0%   -28.91%  (p=0.000 n=7+10)
MapAssignGrow/Int64/18-16                1.67µs ± 0%    1.19µs ± 1%   -28.56%  (p=0.000 n=10+10)
MapAssignGrow/Int64/24-16                2.02µs ± 0%    1.36µs ± 0%   -32.89%  (p=0.000 n=10+10)
MapAssignGrow/Int64/30-16                3.53µs ± 0%    2.53µs ± 0%   -28.19%  (p=0.000 n=8+10)
MapAssignGrow/Int64/64-16                7.84µs ± 1%    5.38µs ± 1%   -31.36%  (p=0.000 n=10+10)
MapAssignGrow/Int64/128-16               15.5µs ± 0%    10.9µs ± 0%   -29.52%  (p=0.000 n=9+10)
MapAssignGrow/Int64/256-16               30.2µs ± 0%    21.9µs ± 0%   -27.59%  (p=0.000 n=10+10)
MapAssignGrow/Int64/512-16               58.8µs ± 0%    43.7µs ± 0%   -25.58%  (p=0.000 n=10+9)
MapAssignGrow/Int64/1024-16               116µs ± 0%      88µs ± 0%   -24.24%  (p=0.000 n=10+9)
MapAssignGrow/Int64/2048-16               231µs ± 0%     175µs ± 0%   -24.04%  (p=0.000 n=10+10)
MapAssignGrow/Int64/4096-16               458µs ± 0%     351µs ± 0%   -23.49%  (p=0.000 n=10+10)
MapAssignGrow/Int64/8192-16               919µs ± 0%     712µs ± 0%   -22.51%  (p=0.000 n=10+10)
MapAssignGrow/Int64/65536-16             8.69ms ± 1%    6.29ms ± 0%   -27.66%  (p=0.000 n=10+7)
MapAssignGrow/Int32/6-16                 71.7ns ± 1%    67.6ns ± 1%    -5.72%  (p=0.000 n=9+10)
MapAssignGrow/Int32/12-16                 734ns ± 0%     521ns ± 0%   -29.00%  (p=0.000 n=9+10)
MapAssignGrow/Int32/18-16                1.61µs ± 1%    1.15µs ± 0%   -28.59%  (p=0.000 n=10+7)
MapAssignGrow/Int32/24-16                1.97µs ± 0%    1.32µs ± 0%   -33.10%  (p=0.000 n=10+9)
MapAssignGrow/Int32/30-16                3.41µs ± 0%    2.43µs ± 1%   -28.67%  (p=0.000 n=10+10)
MapAssignGrow/Int32/64-16                7.45µs ± 0%    5.13µs ± 0%   -31.09%  (p=0.000 n=10+10)
MapAssignGrow/Int32/128-16               15.0µs ± 0%    10.7µs ± 0%   -28.89%  (p=0.000 n=10+9)
MapAssignGrow/Int32/256-16               29.8µs ± 0%    22.0µs ± 1%   -26.05%  (p=0.000 n=9+10)
MapAssignGrow/Int32/512-16               58.1µs ± 0%    42.9µs ± 0%   -26.07%  (p=0.000 n=10+8)
MapAssignGrow/Int32/1024-16               115µs ± 0%      86µs ± 0%   -24.96%  (p=0.000 n=10+10)
MapAssignGrow/Int32/2048-16               226µs ± 1%     171µs ± 1%   -24.44%  (p=0.000 n=10+10)
MapAssignGrow/Int32/4096-16               445µs ± 1%     341µs ± 0%   -23.31%  (p=0.000 n=10+10)
MapAssignGrow/Int32/8192-16               900µs ± 0%     686µs ± 0%   -23.72%  (p=0.000 n=10+10)
MapAssignGrow/Int32/65536-16             7.96ms ± 0%    6.11ms ± 1%   -23.18%  (p=0.000 n=7+10)
MapAssignGrow/Str/6-16                   86.5ns ± 2%    91.6ns ± 2%    +5.88%  (p=0.000 n=10+10)
MapAssignGrow/Str/12-16                   908ns ± 0%     719ns ± 0%   -20.87%  (p=0.000 n=10+10)
MapAssignGrow/Str/18-16                  2.01µs ± 0%    1.59µs ± 0%   -20.98%  (p=0.000 n=7+8)
MapAssignGrow/Str/24-16                  2.36µs ± 0%    1.79µs ± 1%   -23.93%  (p=0.000 n=10+10)
MapAssignGrow/Str/30-16                  4.17µs ± 0%    3.22µs ± 0%   -22.72%  (p=0.000 n=10+10)
MapAssignGrow/Str/64-16                  9.21µs ± 0%    6.73µs ± 0%   -26.96%  (p=0.000 n=7+9)
MapAssignGrow/Str/128-16                 18.6µs ± 0%    13.4µs ± 1%   -27.60%  (p=0.000 n=8+10)
MapAssignGrow/Str/256-16                 35.5µs ± 0%    26.8µs ± 0%   -24.53%  (p=0.000 n=10+10)
MapAssignGrow/Str/512-16                 70.6µs ± 0%    53.3µs ± 0%   -24.58%  (p=0.000 n=10+10)
MapAssignGrow/Str/1024-16                 142µs ± 1%     109µs ± 0%   -23.46%  (p=0.000 n=9+10)
MapAssignGrow/Str/2048-16                 289µs ± 1%     221µs ± 0%   -23.54%  (p=0.000 n=10+9)
MapAssignGrow/Str/4096-16                 588µs ± 0%     448µs ± 0%   -23.83%  (p=0.000 n=9+9)
MapAssignGrow/Str/8192-16                1.27ms ± 1%    0.91ms ± 0%   -28.82%  (p=0.000 n=10+10)
MapAssignGrow/Str/65536-16               12.4ms ± 1%     9.9ms ± 1%   -20.47%  (p=0.000 n=10+9)
MapAssignPreAllocate/Pointer/6-16         310ns ± 1%     281ns ± 0%    -9.41%  (p=0.000 n=10+7)
MapAssignPreAllocate/Pointer/12-16        864ns ± 0%     668ns ± 1%   -22.73%  (p=0.000 n=10+10)
MapAssignPreAllocate/Pointer/18-16       1.31µs ± 0%    0.97µs ± 0%   -25.94%  (p=0.000 n=10+10)
MapAssignPreAllocate/Pointer/24-16       1.77µs ± 0%    1.26µs ± 0%   -29.07%  (p=0.000 n=10+9)
MapAssignPreAllocate/Pointer/30-16       2.16µs ± 0%    1.60µs ± 1%   -26.13%  (p=0.000 n=10+9)
MapAssignPreAllocate/Pointer/64-16       4.73µs ± 1%    3.23µs ± 0%   -31.72%  (p=0.000 n=10+10)
MapAssignPreAllocate/Pointer/128-16      9.18µs ± 0%    6.36µs ± 1%   -30.65%  (p=0.000 n=10+10)
MapAssignPreAllocate/Pointer/256-16      18.0µs ± 0%    12.4µs ± 0%   -30.98%  (p=0.000 n=8+10)
MapAssignPreAllocate/Pointer/512-16      36.2µs ± 1%    24.6µs ± 0%   -32.11%  (p=0.000 n=10+8)
MapAssignPreAllocate/Pointer/1024-16     72.4µs ± 1%    50.3µs ± 0%   -30.49%  (p=0.000 n=10+10)
MapAssignPreAllocate/Pointer/2048-16      145µs ± 1%     102µs ± 0%   -29.93%  (p=0.000 n=10+10)
MapAssignPreAllocate/Pointer/4096-16      291µs ± 0%     209µs ± 1%   -28.18%  (p=0.000 n=10+9)
MapAssignPreAllocate/Pointer/8192-16      590µs ± 0%     444µs ± 1%   -24.76%  (p=0.000 n=10+10)
MapAssignPreAllocate/Pointer/65536-16    6.21ms ± 1%    5.68ms ± 1%    -8.48%  (p=0.000 n=9+9)
MapAssignPreAllocate/Int64/6-16          74.7ns ± 2%    71.2ns ± 2%    -4.68%  (p=0.000 n=10+10)
MapAssignPreAllocate/Int64/12-16          540ns ± 0%     360ns ± 0%   -33.39%  (p=0.000 n=9+9)
MapAssignPreAllocate/Int64/18-16          811ns ± 0%     525ns ± 0%   -35.20%  (p=0.000 n=9+9)
MapAssignPreAllocate/Int64/24-16         1.16µs ± 0%    0.68µs ± 1%   -41.94%  (p=0.000 n=9+10)
MapAssignPreAllocate/Int64/30-16         1.33µs ± 1%    0.87µs ± 1%   -34.60%  (p=0.000 n=10+10)
MapAssignPreAllocate/Int64/64-16         2.97µs ± 1%    1.75µs ± 0%   -41.01%  (p=0.000 n=10+10)
MapAssignPreAllocate/Int64/128-16        5.73µs ± 0%    3.39µs ± 0%   -40.79%  (p=0.000 n=9+8)
MapAssignPreAllocate/Int64/256-16        11.0µs ± 0%     6.5µs ± 0%   -40.50%  (p=0.000 n=10+8)
MapAssignPreAllocate/Int64/512-16        21.8µs ± 0%    12.9µs ± 0%   -40.91%  (p=0.000 n=10+10)
MapAssignPreAllocate/Int64/1024-16       43.6µs ± 0%    26.4µs ± 0%   -39.42%  (p=0.000 n=10+10)
MapAssignPreAllocate/Int64/2048-16       88.0µs ± 1%    52.5µs ± 0%   -40.40%  (p=0.000 n=10+8)
MapAssignPreAllocate/Int64/4096-16        175µs ± 0%     108µs ± 0%   -38.60%  (p=0.000 n=9+10)
MapAssignPreAllocate/Int64/8192-16        362µs ± 0%     224µs ± 1%   -38.10%  (p=0.000 n=8+10)
MapAssignPreAllocate/Int64/65536-16      3.78ms ± 0%    3.21ms ± 2%   -15.14%  (p=0.000 n=10+10)
MapAssignPreAllocate/Int32/6-16          72.8ns ± 1%    69.2ns ± 1%    -4.98%  (p=0.000 n=9+10)
MapAssignPreAllocate/Int32/12-16          503ns ± 0%     342ns ± 0%   -32.02%  (p=0.000 n=10+9)
MapAssignPreAllocate/Int32/18-16          770ns ± 1%     498ns ± 1%   -35.29%  (p=0.000 n=10+8)
MapAssignPreAllocate/Int32/24-16         1.11µs ± 1%    0.65µs ± 0%   -41.79%  (p=0.000 n=10+8)
MapAssignPreAllocate/Int32/30-16         1.26µs ± 0%    0.81µs ± 1%   -35.71%  (p=0.000 n=10+8)
MapAssignPreAllocate/Int32/64-16         2.79µs ± 1%    1.63µs ± 0%   -41.60%  (p=0.000 n=10+9)
MapAssignPreAllocate/Int32/128-16        5.60µs ± 1%    3.39µs ± 1%   -39.52%  (p=0.000 n=10+10)
MapAssignPreAllocate/Int32/256-16        11.1µs ± 1%     6.7µs ± 1%   -39.66%  (p=0.000 n=10+10)
MapAssignPreAllocate/Int32/512-16        21.6µs ± 0%    12.2µs ± 0%   -43.30%  (p=0.000 n=10+10)
MapAssignPreAllocate/Int32/1024-16       42.4µs ± 1%    24.2µs ± 0%   -42.91%  (p=0.000 n=10+10)
MapAssignPreAllocate/Int32/2048-16       84.9µs ± 0%    50.0µs ± 0%   -41.08%  (p=0.000 n=10+8)
MapAssignPreAllocate/Int32/4096-16        173µs ± 0%     104µs ± 0%   -40.04%  (p=0.000 n=10+10)
MapAssignPreAllocate/Int32/8192-16        347µs ± 1%     212µs ± 1%   -39.07%  (p=0.000 n=10+8)
MapAssignPreAllocate/Int32/65536-16      3.69ms ± 1%    3.07ms ± 2%   -16.96%  (p=0.000 n=10+10)
MapAssignPreAllocate/Str/6-16            89.6ns ± 2%    94.6ns ± 1%    +5.49%  (p=0.000 n=9+7)
MapAssignPreAllocate/Str/12-16            641ns ± 1%     504ns ± 0%   -21.37%  (p=0.000 n=9+9)
MapAssignPreAllocate/Str/18-16           1.01µs ± 0%    0.76µs ± 0%   -24.98%  (p=0.000 n=7+8)
MapAssignPreAllocate/Str/24-16           1.36µs ± 0%    0.96µs ± 0%   -29.74%  (p=0.000 n=9+9)
MapAssignPreAllocate/Str/30-16           1.68µs ± 0%    1.22µs ± 0%   -27.15%  (p=0.000 n=10+9)
MapAssignPreAllocate/Str/64-16           3.82µs ± 0%    2.43µs ± 0%   -36.29%  (p=0.000 n=10+10)
MapAssignPreAllocate/Str/128-16          7.60µs ± 0%    4.66µs ± 0%   -38.67%  (p=0.000 n=9+10)
MapAssignPreAllocate/Str/256-16          13.8µs ± 0%     9.2µs ± 0%   -33.55%  (p=0.000 n=10+10)
MapAssignPreAllocate/Str/512-16          27.5µs ± 0%    18.2µs ± 0%   -33.89%  (p=0.000 n=10+9)
MapAssignPreAllocate/Str/1024-16         55.4µs ± 0%    37.8µs ± 0%   -31.90%  (p=0.000 n=10+10)
MapAssignPreAllocate/Str/2048-16          111µs ± 0%      77µs ± 0%   -30.20%  (p=0.000 n=9+9)
MapAssignPreAllocate/Str/4096-16          226µs ± 0%     159µs ± 0%   -29.57%  (p=0.000 n=10+9)
MapAssignPreAllocate/Str/8192-16          481µs ± 0%     368µs ± 1%   -23.34%  (p=0.000 n=9+10)
MapAssignPreAllocate/Str/65536-16        4.83ms ± 1%    4.11ms ± 1%   -14.86%  (p=0.000 n=10+10)
MapAssignReuse/Pointer/6-16               330ns ± 2%     290ns ± 1%   -12.18%  (p=0.000 n=10+10)
MapAssignReuse/Pointer/12-16              757ns ± 1%     550ns ± 1%   -27.35%  (p=0.000 n=9+9)
MapAssignReuse/Pointer/18-16             1.16µs ± 1%    0.81µs ± 1%   -30.13%  (p=0.000 n=9+10)
MapAssignReuse/Pointer/24-16             1.61µs ± 1%    1.08µs ± 1%   -32.59%  (p=0.000 n=8+10)
MapAssignReuse/Pointer/30-16             1.91µs ± 2%    1.31µs ± 1%   -31.72%  (p=0.000 n=10+9)
MapAssignReuse/Pointer/64-16             4.12µs ± 1%    2.75µs ± 1%   -33.26%  (p=0.000 n=8+9)
MapAssignReuse/Pointer/128-16            8.22µs ± 2%    5.50µs ± 1%   -33.03%  (p=0.000 n=10+10)
MapAssignReuse/Pointer/256-16            16.4µs ± 1%    11.0µs ± 1%   -33.01%  (p=0.000 n=9+10)
MapAssignReuse/Pointer/512-16            33.1µs ± 2%    21.9µs ± 1%   -33.72%  (p=0.000 n=10+10)
MapAssignReuse/Pointer/1024-16           66.7µs ± 2%    44.8µs ± 1%   -32.78%  (p=0.000 n=10+9)
MapAssignReuse/Pointer/2048-16            132µs ± 2%      92µs ± 1%   -30.11%  (p=0.000 n=10+10)
MapAssignReuse/Pointer/4096-16            268µs ± 1%     187µs ± 1%   -30.25%  (p=0.000 n=9+10)
MapAssignReuse/Pointer/8192-16            546µs ± 4%     389µs ± 1%   -28.67%  (p=0.000 n=10+10)
MapAssignReuse/Pointer/65536-16          5.14ms ± 3%    4.18ms ± 1%   -18.60%  (p=0.000 n=10+10)
MapAssignReuse/Int64/6-16                81.1ns ± 1%    74.8ns ± 2%    -7.75%  (p=0.000 n=10+10)
MapAssignReuse/Int64/12-16                413ns ± 3%     152ns ± 1%   -63.04%  (p=0.000 n=9+10)
MapAssignReuse/Int64/18-16                429ns ± 3%     223ns ± 1%   -48.00%  (p=0.000 n=8+10)
MapAssignReuse/Int64/24-16               1.01µs ± 4%    0.30µs ± 1%   -69.93%  (p=0.000 n=10+9)
MapAssignReuse/Int64/30-16                618ns ± 3%     358ns ± 2%   -42.00%  (p=0.000 n=9+10)
MapAssignReuse/Int64/64-16               1.31µs ± 1%    0.75µs ± 2%   -42.74%  (p=0.000 n=8+8)
MapAssignReuse/Int64/128-16              2.64µs ± 3%    1.51µs ± 2%   -42.96%  (p=0.000 n=9+10)
MapAssignReuse/Int64/256-16              5.23µs ± 4%    3.00µs ± 2%   -42.59%  (p=0.000 n=10+10)
MapAssignReuse/Int64/512-16              10.3µs ± 3%     6.0µs ± 1%   -41.70%  (p=0.000 n=10+8)
MapAssignReuse/Int64/1024-16             21.0µs ± 2%    12.1µs ± 2%   -42.09%  (p=0.000 n=10+10)
MapAssignReuse/Int64/2048-16             42.2µs ± 2%    25.5µs ± 2%   -39.56%  (p=0.000 n=10+10)
MapAssignReuse/Int64/4096-16             85.3µs ± 3%    51.3µs ± 2%   -39.88%  (p=0.000 n=10+10)
MapAssignReuse/Int64/8192-16              176µs ± 3%     107µs ± 2%   -39.54%  (p=0.000 n=10+10)
MapAssignReuse/Int64/65536-16            1.73ms ± 3%    1.16ms ± 2%   -33.33%  (p=0.000 n=10+10)
MapAssignReuse/Int32/6-16                79.6ns ± 1%    72.4ns ± 2%    -9.14%  (p=0.000 n=10+10)
MapAssignReuse/Int32/12-16                356ns ± 7%     150ns ± 1%   -57.73%  (p=0.000 n=9+10)
MapAssignReuse/Int32/18-16                394ns ± 5%     217ns ± 2%   -44.82%  (p=0.000 n=9+9)
MapAssignReuse/Int32/24-16               1.01µs ± 7%    0.29µs ± 2%   -70.98%  (p=0.000 n=10+10)
MapAssignReuse/Int32/30-16                618ns ± 5%     348ns ± 2%   -43.68%  (p=0.000 n=10+10)
MapAssignReuse/Int32/64-16               1.29µs ± 4%    0.73µs ± 2%   -43.23%  (p=0.000 n=10+10)
MapAssignReuse/Int32/128-16              2.61µs ± 3%    1.46µs ± 2%   -43.88%  (p=0.000 n=10+10)
MapAssignReuse/Int32/256-16              5.21µs ± 3%    2.92µs ± 2%   -43.90%  (p=0.000 n=10+10)
MapAssignReuse/Int32/512-16              10.2µs ± 3%     5.9µs ± 1%   -42.54%  (p=0.000 n=10+9)
MapAssignReuse/Int32/1024-16             20.5µs ± 3%    11.8µs ± 1%   -42.72%  (p=0.000 n=10+9)
MapAssignReuse/Int32/2048-16             41.7µs ± 3%    24.8µs ± 2%   -40.50%  (p=0.000 n=9+10)
MapAssignReuse/Int32/4096-16             84.5µs ± 2%    50.8µs ± 1%   -39.93%  (p=0.000 n=10+9)
MapAssignReuse/Int32/8192-16              170µs ± 1%     103µs ± 2%   -39.52%  (p=0.000 n=10+8)
MapAssignReuse/Int32/65536-16            1.68ms ± 3%    1.12ms ± 2%   -33.25%  (p=0.000 n=10+10)
MapAssignReuse/Str/6-16                  96.8ns ± 3%   102.0ns ± 1%    +5.33%  (p=0.000 n=10+10)
MapAssignReuse/Str/12-16                  491ns ± 3%     202ns ± 1%   -58.99%  (p=0.000 n=8+9)
MapAssignReuse/Str/18-16                  500ns ± 4%     292ns ± 2%   -41.68%  (p=0.000 n=10+10)
MapAssignReuse/Str/24-16                 1.13µs ± 3%    0.40µs ± 1%   -64.33%  (p=0.000 n=9+10)
MapAssignReuse/Str/30-16                  783ns ± 5%     480ns ± 2%   -38.77%  (p=0.000 n=10+10)
MapAssignReuse/Str/64-16                 1.53µs ± 2%    1.02µs ± 2%   -33.00%  (p=0.000 n=10+10)
MapAssignReuse/Str/128-16                3.06µs ± 1%    2.04µs ± 2%   -33.22%  (p=0.000 n=10+10)
MapAssignReuse/Str/256-16                6.15µs ± 3%    4.08µs ± 2%   -33.59%  (p=0.000 n=9+10)
MapAssignReuse/Str/512-16                12.3µs ± 3%     8.2µs ± 1%   -33.49%  (p=0.000 n=10+10)
MapAssignReuse/Str/1024-16               25.3µs ± 2%    17.1µs ± 2%   -32.55%  (p=0.000 n=10+10)
MapAssignReuse/Str/2048-16               50.7µs ± 3%    34.6µs ± 2%   -31.79%  (p=0.000 n=10+10)
MapAssignReuse/Str/4096-16                103µs ± 2%      70µs ± 2%   -31.98%  (p=0.000 n=10+10)
MapAssignReuse/Str/8192-16                218µs ± 1%     157µs ± 2%   -28.32%  (p=0.000 n=9+10)
MapAssignReuse/Str/65536-16              2.03ms ± 1%    1.64ms ± 2%   -19.62%  (p=0.000 n=10+9)
name MapIter/Int/6-16 MapIter/Int/12-16 MapIter/Int/18-16 MapIter/Int/24-16 MapIter/Int/30-16 MapIter/Int/64-16 MapIter/Int/128-16 MapIter/Int/256-16 MapIter/Int/512-16 MapIter/Int/1024-16 MapIter/Int/2048-16 MapIter/Int/4096-16 MapIter/Int/8192-16 MapIter/Int/65536-16 MapAccessHit/Int64/6-16 MapAccessHit/Int64/12-16 MapAccessHit/Int64/18-16 MapAccessHit/Int64/24-16 MapAccessHit/Int64/30-16 MapAccessHit/Int64/64-16 MapAccessHit/Int64/128-16 MapAccessHit/Int64/256-16 MapAccessHit/Int64/512-16 MapAccessHit/Int64/1024-16 MapAccessHit/Int64/2048-16 MapAccessHit/Int64/4096-16 MapAccessHit/Int64/8192-16 MapAccessHit/Int64/65536-16 MapAccessHit/Int32/6-16 MapAccessHit/Int32/12-16 MapAccessHit/Int32/18-16 MapAccessHit/Int32/24-16 MapAccessHit/Int32/30-16 MapAccessHit/Int32/64-16 MapAccessHit/Int32/128-16 MapAccessHit/Int32/256-16 MapAccessHit/Int32/512-16 MapAccessHit/Int32/1024-16 MapAccessHit/Int32/2048-16 MapAccessHit/Int32/4096-16 MapAccessHit/Int32/8192-16 MapAccessHit/Int32/65536-16 MapAccessHit/Str/6-16 MapAccessHit/Str/12-16 MapAccessHit/Str/18-16 MapAccessHit/Str/24-16 MapAccessHit/Str/30-16 MapAccessHit/Str/64-16 MapAccessHit/Str/128-16 MapAccessHit/Str/256-16 MapAccessHit/Str/512-16 MapAccessHit/Str/1024-16 MapAccessHit/Str/2048-16 MapAccessHit/Str/4096-16 MapAccessHit/Str/8192-16 MapAccessHit/Str/65536-16 MapAccessMiss/Int64/6-16 MapAccessMiss/Int64/12-16 MapAccessMiss/Int64/18-16 MapAccessMiss/Int64/24-16 MapAccessMiss/Int64/30-16 MapAccessMiss/Int64/64-16 MapAccessMiss/Int64/128-16 MapAccessMiss/Int64/256-16 MapAccessMiss/Int64/512-16 MapAccessMiss/Int64/1024-16 MapAccessMiss/Int64/2048-16 MapAccessMiss/Int64/4096-16 MapAccessMiss/Int64/8192-16 MapAccessMiss/Int64/65536-16 MapAccessMiss/Int32/6-16 MapAccessMiss/Int32/12-16 MapAccessMiss/Int32/18-16 MapAccessMiss/Int32/24-16 MapAccessMiss/Int32/30-16 MapAccessMiss/Int32/64-16 MapAccessMiss/Int32/128-16 MapAccessMiss/Int32/256-16 MapAccessMiss/Int32/512-16 MapAccessMiss/Int32/1024-16 MapAccessMiss/Int32/2048-16 MapAccessMiss/Int32/4096-16 MapAccessMiss/Int32/8192-16 MapAccessMiss/Int32/65536-16 MapAccessMiss/Str/6-16 MapAccessMiss/Str/12-16 MapAccessMiss/Str/18-16 MapAccessMiss/Str/24-16 MapAccessMiss/Str/30-16 MapAccessMiss/Str/64-16 MapAccessMiss/Str/128-16 MapAccessMiss/Str/256-16 MapAccessMiss/Str/512-16 MapAccessMiss/Str/1024-16 MapAccessMiss/Str/2048-16 MapAccessMiss/Str/4096-16 MapAccessMiss/Str/8192-16 MapAccessMiss/Str/65536-16 MapAssignGrow/Int64/6-16 MapAssignGrow/Int64/12-16 MapAssignGrow/Int64/18-16 MapAssignGrow/Int64/24-16 MapAssignGrow/Int64/30-16 MapAssignGrow/Int64/64-16 MapAssignGrow/Int64/128-16 MapAssignGrow/Int64/256-16 MapAssignGrow/Int64/512-16 MapAssignGrow/Int64/1024-16 MapAssignGrow/Int64/2048-16 MapAssignGrow/Int64/4096-16 MapAssignGrow/Int64/8192-16 MapAssignGrow/Int64/65536-16 MapAssignGrow/Int32/6-16 MapAssignGrow/Int32/12-16 MapAssignGrow/Int32/18-16 MapAssignGrow/Int32/24-16 MapAssignGrow/Int32/30-16 MapAssignGrow/Int32/64-16 MapAssignGrow/Int32/128-16 MapAssignGrow/Int32/256-16 MapAssignGrow/Int32/512-16 MapAssignGrow/Int32/1024-16 MapAssignGrow/Int32/2048-16 MapAssignGrow/Int32/4096-16 MapAssignGrow/Int32/8192-16 MapAssignGrow/Int32/65536-16 MapAssignGrow/Str/6-16 MapAssignGrow/Str/12-16 MapAssignGrow/Str/18-16 MapAssignGrow/Str/24-16 MapAssignGrow/Str/30-16 MapAssignGrow/Str/64-16 MapAssignGrow/Str/128-16 MapAssignGrow/Str/256-16 MapAssignGrow/Str/512-16 MapAssignGrow/Str/1024-16 MapAssignGrow/Str/2048-16 MapAssignGrow/Str/4096-16 MapAssignGrow/Str/8192-16 MapAssignGrow/Str/65536-16 MapAssignPreAllocate/Pointer/6-16 MapAssignPreAllocate/Pointer/12-16 MapAssignPreAllocate/Pointer/18-16 MapAssignPreAllocate/Pointer/24-16 MapAssignPreAllocate/Pointer/30-16 MapAssignPreAllocate/Pointer/64-16 MapAssignPreAllocate/Pointer/128-16 MapAssignPreAllocate/Pointer/256-16 MapAssignPreAllocate/Pointer/512-16 MapAssignPreAllocate/Pointer/1024-16 MapAssignPreAllocate/Pointer/2048-16 MapAssignPreAllocate/Pointer/4096-16 MapAssignPreAllocate/Pointer/8192-16 MapAssignPreAllocate/Pointer/65536-16 MapAssignPreAllocate/Int64/6-16 MapAssignPreAllocate/Int64/12-16 MapAssignPreAllocate/Int64/18-16 MapAssignPreAllocate/Int64/24-16 MapAssignPreAllocate/Int64/30-16 MapAssignPreAllocate/Int64/64-16 MapAssignPreAllocate/Int64/128-16 MapAssignPreAllocate/Int64/256-16 MapAssignPreAllocate/Int64/512-16 MapAssignPreAllocate/Int64/1024-16 MapAssignPreAllocate/Int64/2048-16 MapAssignPreAllocate/Int64/4096-16 MapAssignPreAllocate/Int64/8192-16 MapAssignPreAllocate/Int64/65536-16 MapAssignPreAllocate/Int32/6-16 MapAssignPreAllocate/Int32/12-16 MapAssignPreAllocate/Int32/18-16 MapAssignPreAllocate/Int32/24-16 MapAssignPreAllocate/Int32/30-16 MapAssignPreAllocate/Int32/64-16 MapAssignPreAllocate/Int32/128-16 MapAssignPreAllocate/Int32/256-16 MapAssignPreAllocate/Int32/512-16 MapAssignPreAllocate/Int32/1024-16 MapAssignPreAllocate/Int32/2048-16 MapAssignPreAllocate/Int32/4096-16 MapAssignPreAllocate/Int32/8192-16 MapAssignPreAllocate/Int32/65536-16 MapAssignPreAllocate/Str/6-16 MapAssignPreAllocate/Str/12-16 MapAssignPreAllocate/Str/18-16 MapAssignPreAllocate/Str/24-16 MapAssignPreAllocate/Str/30-16 MapAssignPreAllocate/Str/64-16 MapAssignPreAllocate/Str/128-16 MapAssignPreAllocate/Str/256-16 MapAssignPreAllocate/Str/512-16 MapAssignPreAllocate/Str/1024-16 MapAssignPreAllocate/Str/2048-16 MapAssignPreAllocate/Str/4096-16 MapAssignPreAllocate/Str/8192-16 MapAssignPreAllocate/Str/65536-16 MapAssignReuse/Pointer/6-16 MapAssignReuse/Pointer/12-16 MapAssignReuse/Pointer/18-16 MapAssignReuse/Pointer/24-16 MapAssignReuse/Pointer/30-16 MapAssignReuse/Pointer/64-16 MapAssignReuse/Pointer/128-16 MapAssignReuse/Pointer/256-16 MapAssignReuse/Pointer/512-16 MapAssignReuse/Pointer/1024-16 MapAssignReuse/Pointer/2048-16 MapAssignReuse/Pointer/4096-16 MapAssignReuse/Pointer/8192-16 MapAssignReuse/Pointer/65536-16 MapAssignReuse/Int64/6-16 MapAssignReuse/Int64/12-16 MapAssignReuse/Int64/18-16 MapAssignReuse/Int64/24-16 MapAssignReuse/Int64/30-16 MapAssignReuse/Int64/64-16 MapAssignReuse/Int64/128-16 MapAssignReuse/Int64/256-16 MapAssignReuse/Int64/512-16 MapAssignReuse/Int64/1024-16 MapAssignReuse/Int64/2048-16 MapAssignReuse/Int64/4096-16 MapAssignReuse/Int64/8192-16 MapAssignReuse/Int64/65536-16 MapAssignReuse/Int32/6-16 MapAssignReuse/Int32/12-16 MapAssignReuse/Int32/18-16 MapAssignReuse/Int32/24-16 MapAssignReuse/Int32/30-16 MapAssignReuse/Int32/64-16 MapAssignReuse/Int32/128-16 MapAssignReuse/Int32/256-16 MapAssignReuse/Int32/512-16 MapAssignReuse/Int32/1024-16 MapAssignReuse/Int32/2048-16 MapAssignReuse/Int32/4096-16 MapAssignReuse/Int32/8192-16 MapAssignReuse/Int32/65536-16 MapAssignReuse/Str/6-16 MapAssignReuse/Str/12-16 MapAssignReuse/Str/18-16 MapAssignReuse/Str/24-16 MapAssignReuse/Str/30-16 MapAssignReuse/Str/64-16 MapAssignReuse/Str/128-16 MapAssignReuse/Str/256-16 MapAssignReuse/Str/512-16 MapAssignReuse/Str/1024-16 MapAssignReuse/Str/2048-16 MapAssignReuse/Str/4096-16 MapAssignReuse/Str/8192-16 MapAssignReuse/Str/65536-16

old alloc/op   new alloc/op   delta
 0.00B          0.00B           ~     (all equal)
 0.00B          0.00B           ~     (all equal)
 0.00B          0.00B           ~     (all equal)
 0.00B          0.00B           ~     (all equal)
 0.00B          0.00B           ~     (all equal)
 0.00B          0.00B           ~     (all equal)
 0.00B          0.00B           ~     (all equal)
 0.00B          0.00B           ~     (all equal)
 0.00B          0.00B           ~     (all equal)
 0.00B          0.00B           ~     (all equal)
 0.00B          0.00B           ~     (all equal)
 0.00B          0.00B           ~     (all equal)
 0.00B          0.00B           ~     (all equal)
 0.00B          0.00B           ~     (all equal)
 0.00B          0.00B           ~     (all equal)
 0.00B          0.00B           ~     (all equal)
 0.00B          0.00B           ~     (all equal)
 0.00B          0.00B           ~     (all equal)
 0.00B          0.00B           ~     (all equal)
 0.00B          0.00B           ~     (all equal)
 0.00B          0.00B           ~     (all equal)
 0.00B          0.00B           ~     (all equal)
 0.00B          0.00B           ~     (all equal)
 0.00B          0.00B           ~     (all equal)
 0.00B          0.00B           ~     (all equal)
 0.00B          0.00B           ~     (all equal)
 0.00B          0.00B           ~     (all equal)
 0.00B          0.00B           ~     (all equal)
 0.00B          0.00B           ~     (all equal)
 0.00B          0.00B           ~     (all equal)
 0.00B          0.00B           ~     (all equal)
 0.00B          0.00B           ~     (all equal)
 0.00B          0.00B           ~     (all equal)
 0.00B          0.00B           ~     (all equal)
 0.00B          0.00B           ~     (all equal)
 0.00B          0.00B           ~     (all equal)
 0.00B          0.00B           ~     (all equal)
 0.00B          0.00B           ~     (all equal)
 0.00B          0.00B           ~     (all equal)
 0.00B          0.00B           ~     (all equal)
 0.00B          0.00B           ~     (all equal)
 0.00B          0.00B           ~     (all equal)
 0.00B          0.00B           ~     (all equal)
 0.00B          0.00B           ~     (all equal)
 0.00B          0.00B           ~     (all equal)
 0.00B          0.00B           ~     (all equal)
 0.00B          0.00B           ~     (all equal)
 0.00B          0.00B           ~     (all equal)
 0.00B          0.00B           ~     (all equal)
 0.00B          0.00B           ~     (all equal)
 0.00B          0.00B           ~     (all equal)
 0.00B          0.00B           ~     (all equal)
 0.00B          0.00B           ~     (all equal)
 0.00B          0.00B           ~     (all equal)
 0.00B          0.00B           ~     (all equal)
 0.00B          0.00B           ~     (all equal)
 0.00B          0.00B           ~     (all equal)
 0.00B          0.00B           ~     (all equal)
 0.00B          0.00B           ~     (all equal)
 0.00B          0.00B           ~     (all equal)
 0.00B          0.00B           ~     (all equal)
 0.00B          0.00B           ~     (all equal)
 0.00B          0.00B           ~     (all equal)
 0.00B          0.00B           ~     (all equal)
 0.00B          0.00B           ~     (all equal)
 0.00B          0.00B           ~     (all equal)
 0.00B          0.00B           ~     (all equal)
 0.00B          0.00B           ~     (all equal)
 0.00B          0.00B           ~     (all equal)
 0.00B          0.00B           ~     (all equal)
 0.00B          0.00B           ~     (all equal)
 0.00B          0.00B           ~     (all equal)
 0.00B          0.00B           ~     (all equal)
 0.00B          0.00B           ~     (all equal)
 0.00B          0.00B           ~     (all equal)
 0.00B          0.00B           ~     (all equal)
 0.00B          0.00B           ~     (all equal)
 0.00B          0.00B           ~     (all equal)
 0.00B          0.00B           ~     (all equal)
 0.00B          0.00B           ~     (all equal)
 0.00B          0.00B           ~     (all equal)
 0.00B          0.00B           ~     (all equal)
 0.00B          0.00B           ~     (all equal)
 0.00B          0.00B           ~     (all equal)
 0.00B          0.00B           ~     (all equal)
 0.00B          0.00B           ~     (all equal)
 0.00B          0.00B           ~     (all equal)
 0.00B          0.00B           ~     (all equal)
 0.00B          0.00B           ~     (all equal)
 0.00B          0.00B           ~     (all equal)
 0.00B          0.00B           ~     (all equal)
 0.00B          0.00B           ~     (all equal)
 0.00B          0.00B           ~     (all equal)
 0.00B          0.00B           ~     (all equal)
 0.00B          0.00B           ~     (all equal)
 0.00B          0.00B           ~     (all equal)
 0.00B          0.00B           ~     (all equal)
 0.00B          0.00B           ~     (all equal)
 0.00B          0.00B           ~     (all equal)
 317B ± 0%      288B ± 0%    -9.15%  (p=0.000 n=10+10)
 931B ± 0%      864B ± 0%    -7.20%  (p=0.000 n=10+10)
 1.01kB ± 0%    0.86kB ± 0%   -14.37%  (p=0.000 n=9+10)
 2.22kB ± 0%    2.02kB ± 0%    -9.13%  (p=0.000 n=10+10)
 5.18kB ± 0%    4.32kB ± 0%   -16.55%  (p=0.000 n=10+10)
 10.8kB ± 0%     9.2kB ± 0%   -15.18%  (p=0.000 n=10+10)
 21.5kB ± 0%    18.7kB ± 0%   -13.15%  (p=0.000 n=10+10)
 43.2kB ± 0%    37.1kB ± 0%   -14.11%  (p=0.000 n=10+10)
 86.6kB ± 0%    78.0kB ± 0%    -9.84%  (p=0.000 n=10+10)
 173kB ± 0%     152kB ± 0%   -12.43%  (p=0.000 n=10+10)
 347kB ± 0%     299kB ± 0%   -13.72%  (p=0.000 n=10+8)
 685kB ± 0%     594kB ± 0%   -13.32%  (p=0.000 n=10+8)
 5.45MB ± 0%    4.72MB ± 0%   -13.26%  (p=0.000 n=10+10)
 0.00B          0.00B           ~     (all equal)
 248B ± 0%      224B ± 0%    -9.68%  (p=0.000 n=10+10)
 728B ± 0%      672B ± 0%    -7.69%  (p=0.000 n=10+10)
 793B ± 0%      672B ± 0%   -15.26%  (p=0.000 n=10+10)
 1.74kB ± 0%    1.57kB ± 0%    -9.70%  (p=0.000 n=10+10)
 4.01kB ± 0%    3.36kB ± 0%   -16.15%  (p=0.000 n=9+10)
 8.34kB ± 0%    7.46kB ± 0%   -10.56%  (p=0.000 n=10+10)
 17.0kB ± 0%    15.6kB ± 0%    -7.90%  (p=0.000 n=10+10)
 34.2kB ± 0%    30.0kB ± 0%   -12.26%  (p=0.000 n=10+10)
 68.5kB ± 0%    58.7kB ± 0%   -14.39%  (p=0.000 n=10+10)
 137kB ± 0%     116kB ± 0%   -15.43%  (p=0.000 n=10+10)
 266kB ± 0%     231kB ± 0%   -13.33%  (p=0.000 n=10+10)
 532kB ± 0%     460kB ± 0%   -13.57%  (p=0.000 n=10+10)
 4.25MB ± 0%    3.67MB ± 0%   -13.70%  (p=0.000 n=10+8)
 0.00B          0.00B           ~     (all equal)
 446B ± 0%      416B ± 0%    -6.73%  (p=0.000 n=10+10)
 1.38kB ± 0%    1.31kB ± 0%    -5.13%  (p=0.000 n=10+10)
 1.47kB ± 0%    1.31kB ± 0%   -10.63%  (p=0.000 n=10+10)
 3.32kB ± 0%    3.10kB ± 0%    -6.62%  (p=0.000 n=10+10)
 7.76kB ± 0%    6.56kB ± 0%   -15.42%  (p=0.000 n=10+10)
 16.1kB ± 0%    13.3kB ± 0%   -16.91%  (p=0.000 n=10+10)
 30.5kB ± 0%    26.9kB ± 0%   -11.71%  (p=0.000 n=10+10)
 61.1kB ± 0%    54.2kB ± 0%   -11.30%  (p=0.000 n=10+10)
 122kB ± 0%     112kB ± 0%    -8.66%  (p=0.000 n=10+10)
 244kB ± 0%     218kB ± 0%   -10.63%  (p=0.000 n=10+10)
 487kB ± 0%     431kB ± 0%   -11.58%  (p=0.000 n=10+10)
 974kB ± 0%     857kB ± 0%   -12.05%  (p=0.000 n=10+9)
 7.74MB ± 0%    6.82MB ± 0%   -11.89%  (p=0.000 n=10+10)
 48.0B ± 0%     48.0B ± 0%      ~     (all equal)
 405B ± 0%      384B ± 0%    -5.09%  (p=0.000 n=10+10)
 731B ± 0%      720B ± 0%    -1.50%  (p=0.000 n=10+10)
 837B ± 0%      768B ± 0%    -8.24%  (p=0.000 n=9+10)
 1.40kB ± 0%    1.39kB ± 0%    -0.71%  (p=0.000 n=10+10)
 3.22kB ± 0%    2.82kB ± 0%   -12.66%  (p=0.000 n=10+10)
 6.42kB ± 0%    5.89kB ± 0%    -8.34%  (p=0.000 n=10+10)
 12.3kB ± 0%    11.5kB ± 0%    -6.43%  (p=0.000 n=10+10)
 24.6kB ± 0%    22.5kB ± 0%    -8.42%  (p=0.000 n=10+10)
 49.2kB ± 0%    49.2kB ± 0%    -0.05%  (p=0.000 n=10+10)
 98.3kB ± 0%    90.1kB ± 0%    -8.36%  (p=0.000 n=10+10)
 197kB ± 0%     180kB ± 0%    -8.34%  (p=0.000 n=9+10)
 385kB ± 0%     360kB ± 0%    -6.39%  (p=0.000 n=10+8)
 3.03MB ± 0%    2.88MB ± 0%    -4.87%  (p=0.000 n=10+10)
 0.00B          0.00B           ~     (all equal)
 317B ± 0%      288B ± 0%    -9.15%  (p=0.000 n=10+10)
 591B ± 0%      576B ± 0%    -2.54%  (p=0.000 n=10+10)
 672B ± 0%      576B ± 0%   -14.29%  (p=0.000 n=10+10)
 1.17kB ± 0%    1.15kB ± 0%    -1.20%  (p=0.000 n=10+10)
 2.72kB ± 0%    2.30kB ± 0%   -15.29%  (p=0.000 n=10+10)
 5.42kB ± 0%    4.86kB ± 0%   -10.23%  (p=0.000 n=10+10)
 10.3kB ± 0%     9.5kB ± 0%    -8.03%  (p=0.000 n=10+10)
 20.6kB ± 0%    18.4kB ± 0%   -10.39%  (p=0.000 n=10+10)
 41.1kB ± 0%    41.0kB ± 0%    -0.37%  (p=0.000 n=10+10)
 82.2kB ± 0%    73.7kB ± 0%   -10.30%  (p=0.000 n=10+10)
 164kB ± 0%     147kB ± 0%   -10.29%  (p=0.006 n=7+9)
 321kB ± 0%     295kB ± 0%    -7.99%  (p=0.000 n=10+9)
 2.51MB ± 0%    2.36MB ± 0%    -6.19%  (p=0.000 n=10+10)
 0.00B          0.00B           ~     (all equal)
 248B ± 0%      224B ± 0%    -9.68%  (p=0.000 n=10+10)
 461B ± 0%      448B ± 0%    -2.82%  (p=0.000 n=10+10)
 528B ± 0%      448B ± 0%   -15.15%  (p=0.000 n=10+10)
 908B ± 0%      896B ± 0%    -1.32%  (p=0.000 n=10+10)
 2.08kB ± 0%    1.79kB ± 0%   -13.85%  (p=0.000 n=10+10)
 4.14kB ± 0%    4.10kB ± 0%    -1.01%  (p=0.000 n=10+10)
 8.25kB ± 0%    8.19kB ± 0%    -0.71%  (p=0.000 n=10+10)
 16.5kB ± 0%    14.3kB ± 0%   -12.98%  (p=0.000 n=10+10)
 32.9kB ± 0%    28.7kB ± 0%   -12.91%  (p=0.000 n=10+10)
 65.8kB ± 0%    57.3kB ± 0%   -12.87%  (p=0.000 n=10+10)
 123kB ± 0%     115kB ± 0%    -7.07%  (p=0.000 n=10+10)
 247kB ± 0%     229kB ± 0%    -7.06%  (p=0.000 n=10+10)
 1.96MB ± 0%    1.84MB ± 0%    -6.28%  (p=0.000 n=10+9)
 0.00B          0.00B           ~     (all equal)
 446B ± 0%      416B ± 0%    -6.73%  (p=0.000 n=10+10)
 912B ± 0%      896B ± 0%    -1.75%  (p=0.000 n=10+10)
 1.00kB ± 0%    0.90kB ± 0%   -10.04%  (p=0.002 n=8+10)
 1.81kB ± 0%    1.79kB ± 0%    -0.81%  (p=0.000 n=10+10)
 4.12kB ± 0%    3.46kB ± 0%   -16.12%  (p=0.000 n=10+10)
 8.22kB ± 0%    6.78kB ± 0%   -17.43%  (p=0.000 n=10+10)
 14.4kB ± 0%    13.6kB ± 0%    -5.52%  (p=0.000 n=10+10)
 28.7kB ± 0%    27.3kB ± 0%    -4.99%  (p=0.000 n=10+10)
 57.4kB ± 0%    57.3kB ± 0%    -0.04%  (p=0.000 n=10+10)
 115kB ± 0%     106kB ± 0%    -7.16%  (p=0.000 n=10+10)
 229kB ± 0%     213kB ± 0%    -7.15%  (p=0.000 n=10+8)
 459kB ± 0%     426kB ± 0%    -7.15%  (p=0.001 n=8+9)
 3.62MB ± 0%    3.41MB ± 0%    -5.88%  (p=0.000 n=9+10)
 48.0B ± 0%     48.0B ± 0%      ~     (all equal)
 117B ± 1%       96B ± 0%   -17.74%  (p=0.000 n=10+10)
 155B ± 0%      144B ± 0%    -7.10%  (p=0.000 n=10+10)
 261B ± 0%      192B ± 0%   -26.52%  (p=0.000 n=10+10)
 250B ± 0%      240B ± 0%    -4.00%  (p=0.000 n=10+10)
 512B ± 0%      512B ± 0%      ~     (all equal)
 1.02kB ± 0%    1.02kB ± 0%      ~     (all equal)
 2.05kB ± 0%    2.05kB ± 0%      ~     (all equal)
 4.10kB ± 0%    4.10kB ± 0%      ~     (all equal)
 8.19kB ± 0%    8.19kB ± 0%      ~     (all equal)
 16.4kB ± 0%    16.4kB ± 0%      ~     (all equal)
 32.8kB ± 0%    32.8kB ± 0%      ~     (all equal)
 65.5kB ± 0%    65.5kB ± 0%      ~     (all equal)
 524kB ± 0%     524kB ± 0%      ~     (p=0.137 n=10+8)
 0.00B          0.00B           ~     (all equal)
 25.0B ± 0%      0.0B       -100.00%  (p=0.000 n=10+10)
 13.0B ± 0%      0.0B       -100.00%  (p=0.000 n=10+10)
 85.0B ± 0%      0.0B       -100.00%  (p=0.000 n=10+10)
 12.0B ± 0%      0.0B       -100.00%  (p=0.000 n=10+10)
 8.00B ± 0%     0.00B       -100.00%  (p=0.000 n=10+10)
 18.0B ± 0%      0.0B       -100.00%  (p=0.000 n=10+10)
 34.0B ± 0%      0.0B       -100.00%  (p=0.000 n=10+10)
 66.0B ± 0%      0.0B       -100.00%  (p=0.000 n=10+10)
 128B ± 0%        0B       -100.00%  (p=0.000 n=9+10)
 252B ± 0%        0B       -100.00%  (p=0.000 n=10+10)
 506B ± 0%        0B       -100.00%  (p=0.000 n=10+10)
 1.03kB ± 0%    0.00kB       -100.00%  (p=0.000 n=9+10)
 8.21kB ± 0%    0.00kB       -100.00%  (p=0.000 n=10+10)
 0.00B          0.00B           ~     (all equal)
 20.7B ± 3%      0.0B       -100.00%  (p=0.000 n=10+10)
 11.0B ± 0%      0.0B       -100.00%  (p=0.000 n=10+10)
 69.0B ± 0%      0.0B       -100.00%  (p=0.000 n=10+10)
 10.0B ± 0%      0.0B       -100.00%  (p=0.000 n=10+10)
 8.00B ± 0%     0.00B       -100.00%  (p=0.000 n=10+10)
 18.0B ± 0%      0.0B       -100.00%  (p=0.000 n=10+10)
 34.0B ± 0%      0.0B       -100.00%  (p=0.002 n=8+10)
 66.0B ± 0%      0.0B       -100.00%  (p=0.000 n=10+10)
 128B ± 0%        0B       -100.00%  (p=0.000 n=9+10)
 252B ± 0%        0B       -100.00%  (p=0.000 n=10+10)
 506B ± 0%        0B       -100.00%  (p=0.000 n=10+10)
 1.03kB ± 0%    0.00kB       -100.00%  (p=0.000 n=10+10)
 8.21kB ± 0%    0.00kB       -100.00%  (p=0.000 n=10+10)
 0.00B          0.00B           ~     (all equal)
 30.0B ± 0%      0.0B       -100.00%  (p=0.000 n=10+10)
 16.0B ± 0%      0.0B       -100.00%  (p=0.000 n=10+10)
 100B ± 0%        0B       -100.00%  (p=0.000 n=10+10)
 14.7B ± 5%      0.0B       -100.00%  (p=0.000 n=10+10)
 0.00B          0.00B           ~     (all equal)
 0.00B          0.00B           ~     (all equal)
 0.30B ±233%     0.00B           ~     (p=0.211 n=10+10)
 0.00B          0.00B           ~     (all equal)
 0.00B          0.00B           ~     (all equal)
 0.00B          0.00B           ~     (all equal)
 0.00B          0.00B           ~     (all equal)
 0.00B          0.00B           ~     (all equal)
 0.00B          0.00B           ~     (all equal)
name                                   old allocs/op  new allocs/op  delta

MapIter/Int/6-16                           0.00           0.00           ~     (all equal)

MapIter/Int/12-16                          0.00           0.00           ~     (all equal)

MapIter/Int/18-16                          0.00           0.00           ~     (all equal)

MapIter/Int/24-16                          0.00           0.00           ~     (all equal)

MapIter/Int/30-16                          0.00           0.00           ~     (all equal)

MapIter/Int/64-16                          0.00           0.00           ~     (all equal)

MapIter/Int/128-16                         0.00           0.00           ~     (all equal)

MapIter/Int/256-16                         0.00           0.00           ~     (all equal)

MapIter/Int/512-16                         0.00           0.00           ~     (all equal)

MapIter/Int/1024-16                        0.00           0.00           ~     (all equal)

MapIter/Int/2048-16                        0.00           0.00           ~     (all equal)

MapIter/Int/4096-16                        0.00           0.00           ~     (all equal)

MapIter/Int/8192-16                        0.00           0.00           ~     (all equal)

MapIter/Int/65536-16                       0.00           0.00           ~     (all equal)

MapAccessHit/Int64/6-16                    0.00           0.00           ~     (all equal)

MapAccessHit/Int64/12-16                   0.00           0.00           ~     (all equal)

MapAccessHit/Int64/18-16                   0.00           0.00           ~     (all equal)

MapAccessHit/Int64/24-16                   0.00           0.00           ~     (all equal)

MapAccessHit/Int64/30-16                   0.00           0.00           ~     (all equal)

MapAccessHit/Int64/64-16                   0.00           0.00           ~     (all equal)

MapAccessHit/Int64/128-16                  0.00           0.00           ~     (all equal)

MapAccessHit/Int64/256-16                  0.00           0.00           ~     (all equal)

MapAccessHit/Int64/512-16                  0.00           0.00           ~     (all equal)

MapAccessHit/Int64/1024-16                 0.00           0.00           ~     (all equal)

MapAccessHit/Int64/2048-16                 0.00           0.00           ~     (all equal)

MapAccessHit/Int64/4096-16                 0.00           0.00           ~     (all equal)

MapAccessHit/Int64/8192-16                 0.00           0.00           ~     (all equal)

MapAccessHit/Int64/65536-16                0.00           0.00           ~     (all equal)

MapAccessHit/Int32/6-16                    0.00           0.00           ~     (all equal)

MapAccessHit/Int32/12-16                   0.00           0.00           ~     (all equal)

MapAccessHit/Int32/18-16                   0.00           0.00           ~     (all equal)

MapAccessHit/Int32/24-16                   0.00           0.00           ~     (all equal)

MapAccessHit/Int32/30-16                   0.00           0.00           ~     (all equal)

MapAccessHit/Int32/64-16                   0.00           0.00           ~     (all equal)

MapAccessHit/Int32/128-16                  0.00           0.00           ~     (all equal)

MapAccessHit/Int32/256-16                  0.00           0.00           ~     (all equal)

MapAccessHit/Int32/512-16                  0.00           0.00           ~     (all equal)

MapAccessHit/Int32/1024-16                 0.00           0.00           ~     (all equal)

MapAccessHit/Int32/2048-16                 0.00           0.00           ~     (all equal)

MapAccessHit/Int32/4096-16                 0.00           0.00           ~     (all equal)

MapAccessHit/Int32/8192-16                 0.00           0.00           ~     (all equal)

MapAccessHit/Int32/65536-16                0.00           0.00           ~     (all equal)

MapAccessHit/Str/6-16                      0.00           0.00           ~     (all equal)

MapAccessHit/Str/12-16                     0.00           0.00           ~     (all equal)

MapAccessHit/Str/18-16                     0.00           0.00           ~     (all equal)

MapAccessHit/Str/24-16                     0.00           0.00           ~     (all equal)

MapAccessHit/Str/30-16                     0.00           0.00           ~     (all equal)

MapAccessHit/Str/64-16                     0.00           0.00           ~     (all equal)

MapAccessHit/Str/128-16                    0.00           0.00           ~     (all equal)

MapAccessHit/Str/256-16                    0.00           0.00           ~     (all equal)

MapAccessHit/Str/512-16                    0.00           0.00           ~     (all equal)

MapAccessHit/Str/1024-16                   0.00           0.00           ~     (all equal)

MapAccessHit/Str/2048-16                   0.00           0.00           ~     (all equal)

MapAccessHit/Str/4096-16                   0.00           0.00           ~     (all equal)

MapAccessHit/Str/8192-16                   0.00           0.00           ~     (all equal)

MapAccessHit/Str/65536-16                  0.00           0.00           ~     (all equal)

MapAccessMiss/Int64/6-16                   0.00           0.00           ~     (all equal)

MapAccessMiss/Int64/12-16                  0.00           0.00           ~     (all equal)

MapAccessMiss/Int64/18-16                  0.00           0.00           ~     (all equal)

MapAccessMiss/Int64/24-16                  0.00           0.00           ~     (all equal)

MapAccessMiss/Int64/30-16                  0.00           0.00           ~     (all equal)

MapAccessMiss/Int64/64-16                  0.00           0.00           ~     (all equal)

MapAccessMiss/Int64/128-16                 0.00           0.00           ~     (all equal)

MapAccessMiss/Int64/256-16                 0.00           0.00           ~     (all equal)

MapAccessMiss/Int64/512-16                 0.00           0.00           ~     (all equal)

MapAccessMiss/Int64/1024-16                0.00           0.00           ~     (all equal)

MapAccessMiss/Int64/2048-16                0.00           0.00           ~     (all equal)

MapAccessMiss/Int64/4096-16                0.00           0.00           ~     (all equal)

MapAccessMiss/Int64/8192-16                0.00           0.00           ~     (all equal)

MapAccessMiss/Int64/65536-16               0.00           0.00           ~     (all equal)

MapAccessMiss/Int32/6-16                   0.00           0.00           ~     (all equal)

MapAccessMiss/Int32/12-16                  0.00           0.00           ~     (all equal)

MapAccessMiss/Int32/18-16                  0.00           0.00           ~     (all equal)

MapAccessMiss/Int32/24-16                  0.00           0.00           ~     (all equal)

MapAccessMiss/Int32/30-16                  0.00           0.00           ~     (all equal)

MapAccessMiss/Int32/64-16                  0.00           0.00           ~     (all equal)

MapAccessMiss/Int32/128-16                 0.00           0.00           ~     (all equal)

MapAccessMiss/Int32/256-16                 0.00           0.00           ~     (all equal)

MapAccessMiss/Int32/512-16                 0.00           0.00           ~     (all equal)

MapAccessMiss/Int32/1024-16                0.00           0.00           ~     (all equal)

MapAccessMiss/Int32/2048-16                0.00           0.00           ~     (all equal)

MapAccessMiss/Int32/4096-16                0.00           0.00           ~     (all equal)

MapAccessMiss/Int32/8192-16                0.00           0.00           ~     (all equal)

MapAccessMiss/Int32/65536-16               0.00           0.00           ~     (all equal)

MapAccessMiss/Str/6-16                     0.00           0.00           ~     (all equal)

MapAccessMiss/Str/12-16                    0.00           0.00           ~     (all equal)

MapAccessMiss/Str/18-16                    0.00           0.00           ~     (all equal)

MapAccessMiss/Str/24-16                    0.00           0.00           ~     (all equal)

MapAccessMiss/Str/30-16                    0.00           0.00           ~     (all equal)

MapAccessMiss/Str/64-16                    0.00           0.00           ~     (all equal)

MapAccessMiss/Str/128-16                   0.00           0.00           ~     (all equal)

MapAccessMiss/Str/256-16                   0.00           0.00           ~     (all equal)

MapAccessMiss/Str/512-16                   0.00           0.00           ~     (all equal)

MapAccessMiss/Str/1024-16                  0.00           0.00           ~     (all equal)

MapAccessMiss/Str/2048-16                  0.00           0.00           ~     (all equal)

MapAccessMiss/Str/4096-16                  0.00           0.00           ~     (all equal)

MapAccessMiss/Str/8192-16                  0.00           0.00           ~     (all equal)

MapAccessMiss/Str/65536-16                 0.00           0.00           ~     (all equal)

MapAssignGrow/Int64/6-16                   0.00           0.00           ~     (all equal)

MapAssignGrow/Int64/12-16                  1.00 ± 0%      1.00 ± 0%      ~     (all equal)

MapAssignGrow/Int64/18-16                  3.00 ± 0%      2.00 ± 0%   -33.33%  (p=0.000 n=10+10)

MapAssignGrow/Int64/24-16                  4.00 ± 0%      2.00 ± 0%   -50.00%  (p=0.000 n=10+10)

MapAssignGrow/Int64/30-16                  6.00 ± 0%      3.00 ± 0%   -50.00%  (p=0.000 n=10+10)

MapAssignGrow/Int64/64-16                  12.0 ± 0%       4.0 ± 0%   -66.67%  (p=0.000 n=10+10)

MapAssignGrow/Int64/128-16                 19.0 ± 0%       5.0 ± 0%   -73.68%  (p=0.000 n=10+10)

MapAssignGrow/Int64/256-16                 27.0 ± 0%       6.0 ± 0%   -77.78%  (p=0.000 n=10+10)

MapAssignGrow/Int64/512-16                 42.0 ± 0%       7.0 ± 0%   -83.33%  (p=0.000 n=10+10)

MapAssignGrow/Int64/1024-16                64.0 ± 0%       8.0 ± 0%   -87.50%  (p=0.000 n=10+10)

MapAssignGrow/Int64/2048-16                 100 ± 1%         9 ± 0%   -90.96%  (p=0.000 n=10+10)

MapAssignGrow/Int64/4096-16                 162 ± 0%        10 ± 0%   -93.81%  (p=0.000 n=10+10)

MapAssignGrow/Int64/8192-16                 274 ± 0%        11 ± 0%   -95.99%  (p=0.000 n=10+10)

MapAssignGrow/Int64/65536-16              2.35k ± 0%     0.01k ± 0%   -99.40%  (p=0.000 n=10+10)

MapAssignGrow/Int32/6-16                   0.00           0.00           ~     (all equal)

MapAssignGrow/Int32/12-16                  1.00 ± 0%      1.00 ± 0%      ~     (all equal)

MapAssignGrow/Int32/18-16                  3.00 ± 0%      2.00 ± 0%   -33.33%  (p=0.000 n=10+10)

MapAssignGrow/Int32/24-16                  4.00 ± 0%      2.00 ± 0%   -50.00%  (p=0.000 n=10+10)

MapAssignGrow/Int32/30-16                  6.00 ± 0%      3.00 ± 0%   -50.00%  (p=0.000 n=10+10)

MapAssignGrow/Int32/64-16                  12.0 ± 0%       4.0 ± 0%   -66.67%  (p=0.000 n=10+10)

MapAssignGrow/Int32/128-16                 19.0 ± 0%       5.0 ± 0%   -73.68%  (p=0.000 n=10+10)

MapAssignGrow/Int32/256-16                 28.0 ± 0%       6.0 ± 0%   -78.57%  (p=0.000 n=10+10)

MapAssignGrow/Int32/512-16                 41.0 ± 0%       7.0 ± 0%   -82.93%  (p=0.000 n=10+10)

MapAssignGrow/Int32/1024-16                59.0 ± 0%       8.0 ± 0%   -86.44%  (p=0.000 n=10+10)

MapAssignGrow/Int32/2048-16                86.5 ± 1%       9.0 ± 0%   -89.60%  (p=0.000 n=10+10)

MapAssignGrow/Int32/4096-16                 131 ± 1%        10 ± 0%   -92.38%  (p=0.000 n=10+10)

MapAssignGrow/Int32/8192-16                 284 ± 0%        11 ± 0%   -96.13%  (p=0.002 n=8+10)

MapAssignGrow/Int32/65536-16              2.37k ± 0%     0.01k ± 0%   -99.41%  (p=0.000 n=10+10)

MapAssignGrow/Str/6-16                     0.00           0.00           ~     (all equal)

MapAssignGrow/Str/12-16                    1.00 ± 0%      1.00 ± 0%      ~     (all equal)

MapAssignGrow/Str/18-16                    2.00 ± 0%      2.00 ± 0%      ~     (all equal)

MapAssignGrow/Str/24-16                    2.00 ± 0%      2.00 ± 0%      ~     (all equal)

MapAssignGrow/Str/30-16                    4.00 ± 0%      3.00 ± 0%   -25.00%  (p=0.000 n=10+10)

MapAssignGrow/Str/64-16                    7.00 ± 0%      4.00 ± 0%   -42.86%  (p=0.000 n=10+10)

MapAssignGrow/Str/128-16                   9.00 ± 0%      5.00 ± 0%   -44.44%  (p=0.000 n=10+10)

MapAssignGrow/Str/256-16                   10.0 ± 0%       6.0 ± 0%   -40.00%  (p=0.000 n=10+10)

MapAssignGrow/Str/512-16                   20.0 ± 0%       7.0 ± 0%   -65.00%  (p=0.000 n=10+10)

MapAssignGrow/Str/1024-16                  39.0 ± 0%       8.0 ± 0%   -79.49%  (p=0.000 n=10+10)

MapAssignGrow/Str/2048-16                  74.0 ± 0%       9.0 ± 0%   -87.84%  (p=0.000 n=10+10)

MapAssignGrow/Str/4096-16                   143 ± 0%        10 ± 0%   -93.01%  (p=0.000 n=10+10)

MapAssignGrow/Str/8192-16                   280 ± 0%        11 ± 0%   -96.07%  (p=0.002 n=8+10)

MapAssignGrow/Str/65536-16                2.33k ± 0%     0.01k ± 0%   -99.40%  (p=0.000 n=10+10)

MapAssignPreAllocate/Pointer/6-16          6.00 ± 0%      6.00 ± 0%      ~     (all equal)

MapAssignPreAllocate/Pointer/12-16         13.0 ± 0%      13.0 ± 0%      ~     (all equal)

MapAssignPreAllocate/Pointer/18-16         19.0 ± 0%      19.0 ± 0%      ~     (all equal)

MapAssignPreAllocate/Pointer/24-16         25.0 ± 0%      25.0 ± 0%      ~     (all equal)

MapAssignPreAllocate/Pointer/30-16         31.0 ± 0%      31.0 ± 0%      ~     (all equal)

MapAssignPreAllocate/Pointer/64-16         66.0 ± 0%      65.0 ± 0%    -1.52%  (p=0.000 n=10+10)

MapAssignPreAllocate/Pointer/128-16         130 ± 0%       129 ± 0%    -0.77%  (p=0.000 n=10+10)

MapAssignPreAllocate/Pointer/256-16         258 ± 0%       257 ± 0%    -0.39%  (p=0.000 n=10+10)

MapAssignPreAllocate/Pointer/512-16         514 ± 0%       513 ± 0%    -0.19%  (p=0.000 n=10+10)

MapAssignPreAllocate/Pointer/1024-16      1.03k ± 0%     1.02k ± 0%    -0.10%  (p=0.000 n=10+10)

MapAssignPreAllocate/Pointer/2048-16      2.05k ± 0%     2.05k ± 0%    -0.05%  (p=0.000 n=10+10)

MapAssignPreAllocate/Pointer/4096-16      4.10k ± 0%     4.10k ± 0%    -0.02%  (p=0.000 n=10+10)

MapAssignPreAllocate/Pointer/8192-16      8.19k ± 0%     8.19k ± 0%    -0.01%  (p=0.000 n=10+10)

MapAssignPreAllocate/Pointer/65536-16     65.5k ± 0%     65.5k ± 0%    -0.00%  (p=0.000 n=10+10)

MapAssignPreAllocate/Int64/6-16            0.00           0.00           ~     (all equal)

MapAssignPreAllocate/Int64/12-16           1.00 ± 0%      1.00 ± 0%      ~     (all equal)

MapAssignPreAllocate/Int64/18-16           1.00 ± 0%      1.00 ± 0%      ~     (all equal)

MapAssignPreAllocate/Int64/24-16           2.00 ± 0%      1.00 ± 0%   -50.00%  (p=0.000 n=10+10)

MapAssignPreAllocate/Int64/30-16           1.00 ± 0%      1.00 ± 0%      ~     (all equal)

MapAssignPreAllocate/Int64/64-16           2.00 ± 0%      1.00 ± 0%   -50.00%  (p=0.000 n=10+10)

MapAssignPreAllocate/Int64/128-16          3.00 ± 0%      1.00 ± 0%   -66.67%  (p=0.000 n=10+10)

MapAssignPreAllocate/Int64/256-16          4.00 ± 0%      1.00 ± 0%   -75.00%  (p=0.000 n=10+10)

MapAssignPreAllocate/Int64/512-16          5.00 ± 0%      1.00 ± 0%   -80.00%  (p=0.000 n=10+10)

MapAssignPreAllocate/Int64/1024-16         6.00 ± 0%      1.00 ± 0%   -83.33%  (p=0.000 n=10+10)

MapAssignPreAllocate/Int64/2048-16         7.00 ± 0%      1.00 ± 0%   -85.71%  (p=0.000 n=10+10)

MapAssignPreAllocate/Int64/4096-16         8.00 ± 0%      1.00 ± 0%   -87.50%  (p=0.000 n=10+10)

MapAssignPreAllocate/Int64/8192-16         9.00 ± 0%      1.00 ± 0%   -88.89%  (p=0.000 n=10+10)

MapAssignPreAllocate/Int64/65536-16        13.0 ± 0%       1.0 ± 0%   -92.31%  (p=0.000 n=10+10)

MapAssignPreAllocate/Int32/6-16            0.00           0.00           ~     (all equal)

MapAssignPreAllocate/Int32/12-16           1.00 ± 0%      1.00 ± 0%      ~     (all equal)

MapAssignPreAllocate/Int32/18-16           1.00 ± 0%      1.00 ± 0%      ~     (all equal)

MapAssignPreAllocate/Int32/24-16           2.00 ± 0%      1.00 ± 0%   -50.00%  (p=0.000 n=10+10)

MapAssignPreAllocate/Int32/30-16           1.00 ± 0%      1.00 ± 0%      ~     (all equal)

MapAssignPreAllocate/Int32/64-16           2.00 ± 0%      1.00 ± 0%   -50.00%  (p=0.000 n=10+10)

MapAssignPreAllocate/Int32/128-16          3.00 ± 0%      1.00 ± 0%   -66.67%  (p=0.000 n=10+10)

MapAssignPreAllocate/Int32/256-16          4.00 ± 0%      1.00 ± 0%   -75.00%  (p=0.000 n=10+10)

MapAssignPreAllocate/Int32/512-16          5.00 ± 0%      1.00 ± 0%   -80.00%  (p=0.000 n=10+10)

MapAssignPreAllocate/Int32/1024-16         6.00 ± 0%      1.00 ± 0%   -83.33%  (p=0.000 n=10+10)

MapAssignPreAllocate/Int32/2048-16         7.00 ± 0%      1.00 ± 0%   -85.71%  (p=0.000 n=10+10)

MapAssignPreAllocate/Int32/4096-16         8.00 ± 0%      1.00 ± 0%   -87.50%  (p=0.000 n=10+10)

MapAssignPreAllocate/Int32/8192-16         9.00 ± 0%      1.00 ± 0%   -88.89%  (p=0.000 n=10+10)

MapAssignPreAllocate/Int32/65536-16        13.0 ± 0%       1.0 ± 0%   -92.31%  (p=0.000 n=10+10)

MapAssignPreAllocate/Str/6-16              0.00           0.00           ~     (all equal)

MapAssignPreAllocate/Str/12-16             1.00 ± 0%      1.00 ± 0%      ~     (all equal)

MapAssignPreAllocate/Str/18-16             1.00 ± 0%      1.00 ± 0%      ~     (all equal)

MapAssignPreAllocate/Str/24-16             1.00 ± 0%      1.00 ± 0%      ~     (all equal)

MapAssignPreAllocate/Str/30-16             1.00 ± 0%      1.00 ± 0%      ~     (all equal)

MapAssignPreAllocate/Str/64-16             2.00 ± 0%      1.00 ± 0%   -50.00%  (p=0.000 n=10+10)

MapAssignPreAllocate/Str/128-16            2.00 ± 0%      1.00 ± 0%   -50.00%  (p=0.000 n=10+10)

MapAssignPreAllocate/Str/256-16            2.00 ± 0%      1.00 ± 0%   -50.00%  (p=0.000 n=10+10)

MapAssignPreAllocate/Str/512-16            2.00 ± 0%      1.00 ± 0%   -50.00%  (p=0.000 n=10+10)

MapAssignPreAllocate/Str/1024-16           2.00 ± 0%      1.00 ± 0%   -50.00%  (p=0.000 n=10+10)

MapAssignPreAllocate/Str/2048-16           2.00 ± 0%      1.00 ± 0%   -50.00%  (p=0.000 n=10+10)

MapAssignPreAllocate/Str/4096-16           2.00 ± 0%      1.00 ± 0%   -50.00%  (p=0.000 n=10+10)

MapAssignPreAllocate/Str/8192-16           2.00 ± 0%      1.00 ± 0%   -50.00%  (p=0.000 n=10+10)

MapAssignPreAllocate/Str/65536-16          2.00 ± 0%      1.00 ± 0%   -50.00%  (p=0.000 n=10+10)

MapAssignReuse/Pointer/6-16                6.00 ± 0%      6.00 ± 0%      ~     (all equal)

MapAssignReuse/Pointer/12-16               12.0 ± 0%      12.0 ± 0%      ~     (all equal)

MapAssignReuse/Pointer/18-16               18.0 ± 0%      18.0 ± 0%      ~     (all equal)

MapAssignReuse/Pointer/24-16               24.0 ± 0%      24.0 ± 0%      ~     (all equal)

MapAssignReuse/Pointer/30-16               30.0 ± 0%      30.0 ± 0%      ~     (all equal)

MapAssignReuse/Pointer/64-16               64.0 ± 0%      64.0 ± 0%      ~     (all equal)

MapAssignReuse/Pointer/128-16               128 ± 0%       128 ± 0%      ~     (all equal)

MapAssignReuse/Pointer/256-16               256 ± 0%       256 ± 0%      ~     (all equal)

MapAssignReuse/Pointer/512-16               512 ± 0%       512 ± 0%      ~     (all equal)

MapAssignReuse/Pointer/1024-16            1.02k ± 0%     1.02k ± 0%      ~     (all equal)

MapAssignReuse/Pointer/2048-16            2.05k ± 0%     2.05k ± 0%      ~     (all equal)

MapAssignReuse/Pointer/4096-16            4.10k ± 0%     4.10k ± 0%      ~     (all equal)

MapAssignReuse/Pointer/8192-16            8.19k ± 0%     8.19k ± 0%      ~     (all equal)

MapAssignReuse/Pointer/65536-16           65.5k ± 0%     65.5k ± 0%      ~     (all equal)

MapAssignReuse/Int64/6-16                  0.00           0.00           ~     (all equal)

MapAssignReuse/Int64/12-16                 0.00           0.00           ~     (all equal)

MapAssignReuse/Int64/18-16                 0.00           0.00           ~     (all equal)

MapAssignReuse/Int64/24-16                 1.00 ± 0%      0.00       -100.00%  (p=0.000 n=10+10)

MapAssignReuse/Int64/30-16                 0.00           0.00           ~     (all equal)

MapAssignReuse/Int64/64-16                 0.00           0.00           ~     (all equal)

MapAssignReuse/Int64/128-16                1.00 ± 0%      0.00       -100.00%  (p=0.000 n=10+10)

MapAssignReuse/Int64/256-16                2.00 ± 0%      0.00       -100.00%  (p=0.000 n=10+10)

MapAssignReuse/Int64/512-16                3.00 ± 0%      0.00       -100.00%  (p=0.000 n=10+10)

MapAssignReuse/Int64/1024-16               4.00 ± 0%      0.00       -100.00%  (p=0.000 n=10+10)

MapAssignReuse/Int64/2048-16               5.00 ± 0%      0.00       -100.00%  (p=0.000 n=10+10)

MapAssignReuse/Int64/4096-16               6.00 ± 0%      0.00       -100.00%  (p=0.000 n=10+10)

MapAssignReuse/Int64/8192-16               7.00 ± 0%      0.00       -100.00%  (p=0.000 n=10+10)

MapAssignReuse/Int64/65536-16              11.0 ± 0%       0.0       -100.00%  (p=0.000 n=10+10)

MapAssignReuse/Int32/6-16                  0.00           0.00           ~     (all equal)

MapAssignReuse/Int32/12-16                 0.00           0.00           ~     (all equal)

MapAssignReuse/Int32/18-16                 0.00           0.00           ~     (all equal)

MapAssignReuse/Int32/24-16                 1.00 ± 0%      0.00       -100.00%  (p=0.000 n=10+10)

MapAssignReuse/Int32/30-16                 0.00           0.00           ~     (all equal)

MapAssignReuse/Int32/64-16                 0.00           0.00           ~     (all equal)

MapAssignReuse/Int32/128-16                1.00 ± 0%      0.00       -100.00%  (p=0.000 n=10+10)

MapAssignReuse/Int32/256-16                2.00 ± 0%      0.00       -100.00%  (p=0.000 n=10+10)

MapAssignReuse/Int32/512-16                3.00 ± 0%      0.00       -100.00%  (p=0.000 n=10+10)

MapAssignReuse/Int32/1024-16               4.00 ± 0%      0.00       -100.00%  (p=0.000 n=10+10)

MapAssignReuse/Int32/2048-16               5.00 ± 0%      0.00       -100.00%  (p=0.000 n=10+10)

MapAssignReuse/Int32/4096-16               6.00 ± 0%      0.00       -100.00%  (p=0.000 n=10+10)

MapAssignReuse/Int32/8192-16               7.00 ± 0%      0.00       -100.00%  (p=0.000 n=10+10)

MapAssignReuse/Int32/65536-16              11.0 ± 0%       0.0       -100.00%  (p=0.000 n=10+10)

MapAssignReuse/Str/6-16                    0.00           0.00           ~     (all equal)

MapAssignReuse/Str/12-16                   0.00           0.00           ~     (all equal)

MapAssignReuse/Str/18-16                   0.00           0.00           ~     (all equal)

MapAssignReuse/Str/24-16                   0.00           0.00           ~     (all equal)

MapAssignReuse/Str/30-16                   0.00           0.00           ~     (all equal)

MapAssignReuse/Str/64-16                   0.00           0.00           ~     (all equal)

MapAssignReuse/Str/128-16                  0.00           0.00           ~     (all equal)

MapAssignReuse/Str/256-16                  0.00           0.00           ~     (all equal)

MapAssignReuse/Str/512-16                  0.00           0.00           ~     (all equal)

MapAssignReuse/Str/1024-16                 0.00           0.00           ~     (all equal)

MapAssignReuse/Str/2048-16                 0.00           0.00           ~     (all equal)

MapAssignReuse/Str/4096-16                 0.00           0.00           ~     (all equal)

MapAssignReuse/Str/8192-16                 0.00           0.00           ~     (all equal)

MapAssignReuse/Str/65536-16                0.00           0.00           ~     (all equal)

Benchmark-2

The benchmarks from runtime.

INFO

name                              old time/op    new time/op      delta
MegMap-16                           9.01ns ± 1%      8.83ns ± 1%       -2.00%  (p=0.000 n=8+8)
MegOneMap-16                        4.59ns ± 1%      9.21ns ± 2%     +100.52%  (p=0.000 n=9+10)
MegEqMap-16                         20.4µs ± 2%      20.1µs ± 2%       -1.49%  (p=0.011 n=9+9)
MegEmptyMap-16                      2.18ns ± 3%      2.06ns ± 1%       -5.42%  (p=0.000 n=10+10)
SmallStrMap-16                      8.27ns ± 1%      7.17ns ± 4%      -13.31%  (p=0.000 n=8+10)
MapStringKeysEight_16-16            6.89ns ± 3%      7.79ns ± 1%      +13.09%  (p=0.000 n=9+8)
MapStringKeysEight_32-16            7.75ns ± 5%      7.97ns ± 0%       +2.83%  (p=0.000 n=10+7)
MapStringKeysEight_64-16            7.66ns ± 3%      8.76ns ± 1%      +14.43%  (p=0.000 n=10+7)
MapStringKeysEight_1M-16            7.72ns ± 3%  16483.00ns ± 1%  +213363.36%  (p=0.000 n=10+8)
IntMap-16                           5.21ns ± 1%      6.42ns ±16%      +23.30%  (p=0.000 n=8+10)
MapFirst/1-16                       2.68ns ± 1%      2.45ns ± 1%       -8.78%  (p=0.000 n=10+9)
MapFirst/2-16                       2.68ns ± 1%      2.43ns ± 1%       -9.34%  (p=0.000 n=9+9)
MapFirst/3-16                       2.66ns ± 2%      2.44ns ± 1%       -7.98%  (p=0.000 n=10+9)
MapFirst/4-16                       2.68ns ± 1%      2.44ns ± 0%       -8.67%  (p=0.000 n=8+9)
MapFirst/5-16                       2.69ns ± 1%      2.45ns ± 0%       -8.73%  (p=0.000 n=8+8)
MapFirst/6-16                       2.68ns ± 0%      2.44ns ± 1%       -8.78%  (p=0.000 n=8+9)
MapFirst/7-16                       2.69ns ± 1%      2.45ns ± 1%       -9.10%  (p=0.000 n=10+9)
MapFirst/8-16                       2.67ns ± 1%      4.79ns ± 1%      +79.47%  (p=0.000 n=10+9)
MapFirst/9-16                       4.66ns ± 1%      4.75ns ± 2%       +1.98%  (p=0.000 n=10+9)
MapFirst/10-16                      4.68ns ± 2%      4.73ns ± 1%       +1.19%  (p=0.016 n=9+10)
MapFirst/11-16                      4.69ns ± 2%      4.78ns ± 1%       +1.93%  (p=0.000 n=9+8)
MapFirst/12-16                      4.64ns ± 2%      4.75ns ± 2%       +2.47%  (p=0.005 n=10+10)
MapFirst/13-16                      4.69ns ± 1%      4.78ns ± 1%       +1.86%  (p=0.000 n=8+9)
MapFirst/14-16                      4.68ns ± 2%      4.79ns ± 1%       +2.34%  (p=0.000 n=10+8)
MapFirst/15-16                      4.67ns ± 1%      6.90ns ± 2%      +47.88%  (p=0.000 n=8+10)
MapFirst/16-16                      4.65ns ± 2%      6.95ns ± 1%      +49.60%  (p=0.000 n=10+9)
MapMid/1-16                         2.68ns ± 1%      2.62ns ± 1%       -2.15%  (p=0.000 n=10+9)
MapMid/2-16                         3.23ns ± 1%      2.95ns ± 1%       -8.59%  (p=0.000 n=10+9)
MapMid/3-16                         3.21ns ± 1%      2.94ns ± 0%       -8.33%  (p=0.000 n=10+7)
MapMid/4-16                         3.64ns ± 2%      3.46ns ± 1%       -4.84%  (p=0.000 n=10+8)
MapMid/5-16                         3.67ns ± 1%      3.47ns ± 1%       -5.46%  (p=0.000 n=10+8)
MapMid/6-16                         4.15ns ± 2%      3.93ns ± 1%       -5.25%  (p=0.000 n=10+9)
MapMid/7-16                         4.19ns ± 1%      3.91ns ± 1%       -6.55%  (p=0.000 n=10+10)
MapMid/8-16                         4.84ns ± 2%      5.76ns ±11%      +19.02%  (p=0.000 n=10+10)
MapMid/9-16                         5.66ns ±10%      5.83ns ± 9%         ~     (p=0.393 n=10+10)
MapMid/10-16                        5.81ns ± 5%      6.20ns ± 4%       +6.67%  (p=0.001 n=8+7)
MapMid/11-16                        5.80ns ± 4%      6.17ns ±11%         ~     (p=0.278 n=9+10)
MapMid/12-16                        5.87ns ±10%      6.26ns ± 2%       +6.48%  (p=0.008 n=9+7)
MapMid/13-16                        6.15ns ±13%      5.92ns ± 8%         ~     (p=0.315 n=10+8)
MapMid/14-16                        5.29ns ± 8%      6.18ns ±14%      +16.89%  (p=0.001 n=9+10)
MapMid/15-16                        5.44ns ±12%      7.04ns ± 2%      +29.37%  (p=0.000 n=10+10)
MapMid/16-16                        5.91ns ±11%      7.18ns ± 3%      +21.44%  (p=0.000 n=10+9)
MapLast/1-16                        2.69ns ± 1%      2.64ns ± 2%       -2.00%  (p=0.000 n=8+10)
MapLast/2-16                        3.22ns ± 2%      2.93ns ± 1%       -9.05%  (p=0.000 n=9+10)
MapLast/3-16                        3.66ns ± 2%      3.47ns ± 1%       -5.17%  (p=0.000 n=10+8)
MapLast/4-16                        4.20ns ± 1%      3.88ns ± 2%       -7.54%  (p=0.000 n=8+9)
MapLast/5-16                        4.85ns ± 2%      4.39ns ± 2%       -9.53%  (p=0.000 n=9+9)
MapLast/6-16                        5.33ns ± 1%      5.10ns ± 8%       -4.27%  (p=0.017 n=9+10)
MapLast/7-16                        5.79ns ± 1%      5.33ns ± 2%       -7.93%  (p=0.000 n=9+8)
MapLast/8-16                        6.28ns ± 1%      6.55ns ±17%         ~     (p=0.704 n=9+10)
MapLast/9-16                        6.90ns ±18%      6.87ns ±12%         ~     (p=1.000 n=9+9)
MapLast/10-16                       6.83ns ±15%      7.32ns ± 7%       +7.10%  (p=0.010 n=9+8)
MapLast/11-16                       7.84ns ± 3%      7.46ns ± 5%       -4.78%  (p=0.006 n=7+8)
MapLast/12-16                       7.58ns ± 9%      7.58ns ±12%         ~     (p=0.743 n=8+9)
MapLast/13-16                       9.15ns ±25%     14.06ns ± 2%      +53.70%  (p=0.000 n=10+8)
MapLast/14-16                       6.31ns ±15%      7.95ns ± 8%      +25.94%  (p=0.000 n=9+8)
MapLast/15-16                       6.20ns ±16%      7.11ns ± 2%      +14.59%  (p=0.004 n=10+10)
MapLast/16-16                       6.78ns ±19%      7.19ns ± 1%         ~     (p=0.139 n=9+8)
MapCycle-16                         11.5ns ± 2%      15.8ns ± 2%      +36.83%  (p=0.000 n=10+10)
RepeatedLookupStrMapKey32-16        9.37ns ± 2%      7.81ns ± 1%      -16.67%  (p=0.000 n=9+9)
RepeatedLookupStrMapKey1M-16        16.6µs ± 1%      16.6µs ± 2%         ~     (p=0.604 n=10+9)
MakeMap/[Byte]Byte-16                120ns ± 1%       116ns ± 1%       -3.61%  (p=0.000 n=10+10)
MakeMap/[Int]Int-16                  164ns ± 1%       160ns ± 0%       -2.36%  (p=0.000 n=10+9)
NewEmptyMap-16                      4.32ns ± 1%      4.55ns ± 3%       +5.26%  (p=0.000 n=10+10)
NewSmallMap-16                      19.4ns ± 2%      24.1ns ± 1%      +24.31%  (p=0.000 n=10+10)
MapIter-16                          73.7ns ± 2%      82.3ns ± 3%      +11.60%  (p=0.000 n=10+10)
MapIterEmpty-16                     3.65ns ± 1%      4.11ns ± 2%      +12.80%  (p=0.000 n=9+9)
SameLengthMap-16                    3.14ns ± 2%      3.38ns ± 2%       +7.50%  (p=0.000 n=9+10)
BigKeyMap-16                        10.0ns ± 4%      11.9ns ± 1%      +18.84%  (p=0.000 n=10+10)
BigValMap-16                        10.0ns ± 3%      11.9ns ± 2%      +18.74%  (p=0.000 n=10+10)
SmallKeyMap-16                      8.51ns ± 1%      9.91ns ± 1%      +16.44%  (p=0.000 n=10+9)
MapPopulate/1-16                    10.4ns ± 1%      14.4ns ± 2%      +38.28%  (p=0.000 n=9+9)
MapPopulate/10-16                    608ns ± 1%       495ns ± 1%      -18.58%  (p=0.000 n=10+10)
MapPopulate/100-16                  9.32µs ± 1%      6.28µs ± 1%      -32.59%  (p=0.000 n=9+10)
MapPopulate/1000-16                  111µs ± 0%        86µs ± 0%      -22.28%  (p=0.000 n=10+10)
MapPopulate/10000-16                 965µs ± 0%       745µs ± 1%      -22.78%  (p=0.000 n=10+10)
MapPopulate/100000-16               10.4ms ± 1%       7.4ms ± 0%      -28.46%  (p=0.000 n=10+10)
ComplexAlgMap-16                    20.6ns ± 1%      22.9ns ± 1%      +10.86%  (p=0.000 n=9+10)
GoMapClear/Reflexive/1-16           19.3ns ± 1%      17.9ns ± 1%       -7.39%  (p=0.000 n=10+10)
GoMapClear/Reflexive/10-16          21.2ns ± 1%      18.9ns ± 2%      -10.91%  (p=0.000 n=10+9)
GoMapClear/Reflexive/100-16         37.3ns ± 1%      40.2ns ± 1%       +7.90%  (p=0.000 n=9+9)
GoMapClear/Reflexive/1000-16         345ns ± 2%       433ns ± 1%      +25.73%  (p=0.000 n=10+10)
GoMapClear/Reflexive/10000-16       2.62µs ± 1%      3.94µs ± 1%      +50.33%  (p=0.000 n=10+10)
GoMapClear/NonReflexive/1-16        80.2ns ± 2%      62.8ns ± 2%      -21.61%  (p=0.000 n=9+9)
GoMapClear/NonReflexive/10-16       92.2ns ± 2%      72.5ns ± 2%      -21.42%  (p=0.000 n=10+10)
GoMapClear/NonReflexive/100-16       216ns ± 2%       101ns ± 1%      -53.49%  (p=0.000 n=9+8)
GoMapClear/NonReflexive/1000-16     2.13µs ± 1%      0.34µs ± 2%      -84.02%  (p=0.000 n=10+9)
GoMapClear/NonReflexive/10000-16    16.4µs ± 1%       2.1µs ± 1%      -86.96%  (p=0.000 n=10+8)
MapStringConversion/32/simple-16    7.79ns ± 1%     12.22ns ± 1%      +56.92%  (p=0.000 n=9+9)
MapStringConversion/32/struct-16    7.72ns ± 1%     12.32ns ± 2%      +59.70%  (p=0.000 n=9+10)
MapStringConversion/32/array-16     7.72ns ± 3%     12.00ns ± 3%      +55.34%  (p=0.000 n=10+9)
MapStringConversion/64/simple-16    7.47ns ± 1%     11.77ns ± 3%      +57.65%  (p=0.000 n=9+10)
MapStringConversion/64/struct-16    7.49ns ± 1%     11.94ns ± 2%      +59.38%  (p=0.000 n=9+10)
MapStringConversion/64/array-16     7.50ns ± 1%     11.92ns ± 2%      +58.89%  (p=0.000 n=9+10)
MapInterfaceString-16               11.2ns ± 5%      13.7ns ±61%         ~     (p=1.000 n=8+10)
MapInterfacePtr-16                  10.8ns ±29%      11.3ns ±52%         ~     (p=0.684 n=10+10)
NewEmptyMapHintLessThan8-16         6.54ns ± 1%      6.04ns ± 1%       -7.56%  (p=0.000 n=9+9)
NewEmptyMapHintGreaterThan8-16       271ns ± 2%       268ns ± 1%         ~     (p=0.062 n=10+9)
MapPop100-16                        10.8µs ± 6%       7.2µs ±14%      -33.41%  (p=0.000 n=10+10)
MapPop1000-16                        170µs ± 1%       101µs ± 1%      -40.54%  (p=0.000 n=9+9)
MapPop10000-16                      3.35ms ± 3%      1.74ms ± 4%      -48.15%  (p=0.000 n=10+9)
MapAssign/Int32/256-16              10.1ns ± 4%       8.9ns ± 1%      -12.13%  (p=0.000 n=10+9)
MapAssign/Int32/65536-16            22.0ns ± 1%      12.9ns ± 1%      -41.11%  (p=0.000 n=10+8)
MapAssign/Int64/256-16              10.7ns ± 2%       8.6ns ± 2%      -19.79%  (p=0.000 n=8+9)
MapAssign/Int64/65536-16            23.2ns ± 2%      13.1ns ± 2%      -43.39%  (p=0.000 n=10+9)
MapAssign/Str/256-16                16.6ns ± 4%      13.1ns ± 3%      -21.18%  (p=0.000 n=10+9)
MapAssign/Str/65536-16              27.5ns ± 3%      20.5ns ± 3%      -25.66%  (p=0.000 n=10+9)
MapOperatorAssign/Int32/256-16      9.89ns ± 2%      8.69ns ± 3%      -12.15%  (p=0.000 n=9+9)
MapOperatorAssign/Int32/65536-16    21.9ns ± 1%      12.8ns ± 3%      -41.52%  (p=0.000 n=10+10)
MapOperatorAssign/Int64/256-16      10.9ns ± 3%       8.6ns ± 1%      -21.20%  (p=0.000 n=9+8)
MapOperatorAssign/Int64/65536-16    22.4ns ± 0%      13.2ns ± 2%      -41.15%  (p=0.000 n=7+9)
MapOperatorAssign/Str/256-16        1.43µs ± 2%      1.40µs ± 1%       -1.93%  (p=0.000 n=10+10)
MapOperatorAssign/Str/65536-16       234ns ± 3%       237ns ± 4%         ~     (p=0.138 n=10+10)
MapAppendAssign/Int32/256-16        21.0ns ± 2%      20.1ns ± 4%       -4.43%  (p=0.000 n=8+10)
MapAppendAssign/Int32/65536-16      38.5ns ± 2%      33.9ns ± 2%      -12.00%  (p=0.000 n=10+10)
MapAppendAssign/Int64/256-16        21.4ns ± 3%      20.4ns ± 6%       -4.26%  (p=0.008 n=9+10)
MapAppendAssign/Int64/65536-16      39.8ns ± 2%      34.9ns ± 1%      -12.40%  (p=0.000 n=10+8)
MapAppendAssign/Str/256-16          52.8ns ± 7%      52.1ns ± 5%         ~     (p=0.739 n=10+10)
MapAppendAssign/Str/65536-16        66.5ns ± 2%      67.7ns ± 1%       +1.94%  (p=0.004 n=9+9)
MapDelete/Int32/100-16              27.7ns ± 2%      17.8ns ± 2%      -35.77%  (p=0.000 n=10+10)
MapDelete/Int32/1000-16             22.6ns ± 2%      12.8ns ± 1%      -43.31%  (p=0.000 n=9+9)
MapDelete/Int32/10000-16            25.0ns ± 2%      15.2ns ± 1%      -39.33%  (p=0.000 n=7+10)
MapDelete/Int64/100-16              29.8ns ± 3%      17.6ns ± 2%      -40.98%  (p=0.000 n=10+9)
MapDelete/Int64/1000-16             23.3ns ± 2%      13.1ns ± 1%      -43.77%  (p=0.000 n=10+8)
MapDelete/Int64/10000-16            25.6ns ± 2%      16.1ns ± 1%      -37.13%  (p=0.000 n=9+9)
MapDelete/Str/100-16                38.4ns ± 4%      24.8ns ± 2%      -35.29%  (p=0.000 n=10+10)
MapDelete/Str/1000-16               30.8ns ± 2%      20.7ns ± 1%      -32.72%  (p=0.000 n=10+10)
MapDelete/Str/10000-16              35.8ns ± 2%      24.4ns ± 2%      -31.95%  (p=0.000 n=10+10)
MapDelete/Pointer/100-16            30.7ns ± 2%      21.0ns ± 1%      -31.69%  (p=0.000 n=10+10)
MapDelete/Pointer/1000-16           24.5ns ± 2%      16.6ns ± 1%      -32.37%  (p=0.000 n=10+10)
MapDelete/Pointer/10000-16          27.1ns ± 3%      19.8ns ± 2%      -26.87%  (p=0.000 n=10+10)
name                              old alloc/op   new alloc/op     delta

NewEmptyMap-16                       0.00B            0.00B              ~     (all equal)

NewSmallMap-16                       0.00B            0.00B              ~     (all equal)

MapPopulate/1-16                     0.00B            0.00B              ~     (all equal)

MapPopulate/10-16                     179B ± 0%        176B ± 0%       -1.68%  (p=0.000 n=10+10)

MapPopulate/100-16                  3.35kB ± 0%      2.64kB ± 0%      -21.16%  (p=0.000 n=10+10)

MapPopulate/1000-16                 53.3kB ± 0%      48.7kB ± 0%       -8.62%  (p=0.000 n=9+10)

MapPopulate/10000-16                 428kB ± 0%       368kB ± 0%      -13.87%  (p=0.000 n=9+10)

MapPopulate/100000-16               3.62MB ± 0%      2.89MB ± 0%      -20.08%  (p=0.000 n=8+10)

MapStringConversion/32/simple-16     0.00B            0.00B              ~     (all equal)

MapStringConversion/32/struct-16     0.00B            0.00B              ~     (all equal)

MapStringConversion/32/array-16      0.00B            0.00B              ~     (all equal)

MapStringConversion/64/simple-16     0.00B            0.00B              ~     (all equal)

MapStringConversion/64/struct-16     0.00B            0.00B              ~     (all equal)

MapStringConversion/64/array-16      0.00B            0.00B              ~     (all equal)

NewEmptyMapHintLessThan8-16          0.00B            0.00B              ~     (all equal)

NewEmptyMapHintGreaterThan8-16      1.15kB ± 0%      1.15kB ± 0%         ~     (all equal)

MapAppendAssign/Int32/256-16         45.5B ± 3%       43.5B ±13%         ~     (p=0.291 n=8+10)

MapAppendAssign/Int32/65536-16       18.3B ± 4%       16.7B ± 4%       -8.74%  (p=0.000 n=10+10)

MapAppendAssign/Int64/256-16         42.8B ±12%       44.5B ±15%         ~     (p=0.466 n=10+10)

MapAppendAssign/Int64/65536-16       18.6B ± 8%       17.0B ± 0%       -8.60%  (p=0.000 n=10+9)

MapAppendAssign/Str/256-16           88.1B ± 4%       87.9B ± 4%         ~     (p=1.000 n=10+10)

MapAppendAssign/Str/65536-16         35.0B ± 0%       33.4B ± 4%       -4.57%  (p=0.000 n=6+10)
name                              old allocs/op  new allocs/op    delta

NewEmptyMap-16                        0.00             0.00              ~     (all equal)

NewSmallMap-16                        0.00             0.00              ~     (all equal)

MapPopulate/1-16                      0.00             0.00              ~     (all equal)

MapPopulate/10-16                     1.00 ± 0%        1.00 ± 0%         ~     (all equal)

MapPopulate/100-16                    17.0 ± 0%         4.0 ± 0%      -76.47%  (p=0.000 n=10+10)

MapPopulate/1000-16                   72.7 ± 1%         8.0 ± 0%      -89.00%  (p=0.000 n=10+10)

MapPopulate/10000-16                   319 ± 0%          11 ± 0%      -96.55%  (p=0.002 n=8+10)

MapPopulate/100000-16                4.00k ± 0%       0.01k ± 0%      -99.65%  (p=0.000 n=10+10)

MapStringConversion/32/simple-16      0.00             0.00              ~     (all equal)

MapStringConversion/32/struct-16      0.00             0.00              ~     (all equal)

MapStringConversion/32/array-16       0.00             0.00              ~     (all equal)

MapStringConversion/64/simple-16      0.00             0.00              ~     (all equal)

MapStringConversion/64/struct-16      0.00             0.00              ~     (all equal)

MapStringConversion/64/array-16       0.00             0.00              ~     (all equal)

NewEmptyMapHintLessThan8-16           0.00             0.00              ~     (all equal)

NewEmptyMapHintGreaterThan8-16        1.00 ± 0%        1.00 ± 0%         ~     (all equal)

MapAppendAssign/Int32/256-16          0.00             0.00              ~     (all equal)

MapAppendAssign/Int32/65536-16        0.00             0.00              ~     (all equal)

MapAppendAssign/Int64/256-16          0.00             0.00              ~     (all equal)

MapAppendAssign/Int64/65536-16        0.00             0.00              ~     (all equal)

MapAppendAssign/Str/256-16            0.00             0.00              ~     (all equal)

MapAppendAssign/Str/65536-16          0.00             0.00              ~     (all equal)

gopherbot · 2022-08-30T06:51:03Z

Change https://go.dev/cl/426614 mentions this issue: runtime: use SwissTable

seankhliao · 2022-08-30T07:37:39Z

cc @golang/runtime

prattmic · 2022-08-30T14:36:01Z

cc @randall77

Overall this sounds great. The main concern I have up front here is that growing happens all at once rather than incrementally. Could you explain more why that is and if it is possible to do so incrementally?

aaronbee · 2022-08-30T16:45:45Z

Do iterators get invalidated when the map is modified? This is common for open-addressing hash tables. An important feature of the current map is that you can modify the map while iterating and the iterator still works.

aaronbee · 2022-08-30T18:47:42Z

Do iterators get invalidated when the map is modified? This is common for open-addressing hash tables. An important feature of the current map is that you can modify the map while iterating and the iterator still works.

I checked the implementation and it does look like iterators stay valid when the map is modified.

randall77 · 2022-08-30T19:27:05Z

The semantics of Go iterators basically mean you can't move items in the map data structure once you've placed them. So, for instance, you can't move a valid item to fill in a deleted one - you need to always use a tombstone. But other than that, iterators don't add much of a restriction to the implementation.

aclements · 2022-08-31T15:56:35Z

This is really exciting. Thanks for doing all of this work.

The benchmarks from runtime.

There are many slowdowns in these benchmarks, some quite significant. Do you understand the source of these slowdowns? Is it something that can be fixed?

The previous implementation uses incremental rehash

This is an important property to maintain because it can significantly impact the tail latency of services. We've done a lot of work throughout the Go runtime over the years to avoid unpredictable performance spikes and it would be a shame to regress here.

I'm not personally familiar with the details of SwissTable. Is incremental rehashing something that can be done and just hasn't been implemented yet, or is it fundamentally difficult?

If it's fundamentally difficult to do directly in SwissTable, I've been kickaround the the idea of adopting aspects of extendible hashing for a while, which could be a general solution to incremental resizing. I should probably just file an "idea" issue about this, but I'll try to lay it out here.

The idea is that, once a hash table grows beyond some size threshold based on bounding how long it takes to resize a map, you switch to a two-level scheme. I'm guessing that threshold would be around 4MiB, but that would have to be determined experimentally. In the two-level scheme, the top level is an index array keyed by the top k bits of the hash, which then points to map shards, which are individual SwissTables. The Wikipedia article I linked has some good diagrams for visualizing this. Each shard s contains only the items whose top j_s <= k bits are all identical, and multiple index entries will point to the same shard if that shard's j_s < k. When an individual shard overflows the threshold size, you split just that shard into two new shards s1 and s2 with j_s1 = j_s2 = j_s+1, and update the index. If j_s1 > k, then you also double the index array in order to increase k by 1.

This would enable incremental growth and bound the resize cost paid by any single map operation. Iterators can continue to work while a map is resized by holding on to the pre-resize shard they are currently iterating (let the GC collect this once all iterators have moved past it). It would also reduce overall memory footprint because the total memory size of a map doesn't have to be a power of two (even if each individual shard is). It would result in less memory fragmentation caused by large maps because it limits the size of each individual allocation. And it would address problems with our current map resizing algorithm where, if a map is grown to a size that puts it into resizing mode, but then modifications stop and the application switches to only reading from the map, accesses are relatively slow and the map continues to consume additional memory (#51410).

mknyszek · 2022-08-31T19:26:53Z

I placed this in the Unplanned milestone for now since it seems like there's still a bunch to discuss before landing it (it's non-committal). I assigned it to @zhangyunhao116 since you're driving the effort at the moment.

zhangyunhao116 · 2022-09-02T09:28:47Z

Thanks for your advice! @aclements

We hope to get more feedback from the community and the Go team.

Do you understand the source of these slowdowns? Is it something that can be fixed?

Many reasons affect the performance degradation of these benchmarks(for basic version):

Most benchmarks from the Go runtime are running on a small map(contains very few elements). The original implementation has a feature called emptyRest that would break the current loop after encountering it. SwissTable does not have this feature. In this case, the previous implementation is better(the situation is usually reversed with the larger map. ). This affects the performance of BigKeyMap and MapStringConversion. In most cases, the larger the number of map elements, the better performance of the SwissTable.
The Go runtime's mapaccess benchmarks only test the hit case ( MapFirst MapMid MapLast). SwissTable tends to perform better in the case of Miss.
The growth of SwissTable is done at once, which means in some cases, the performance will be significantly degraded. For MapStringKeysEight, because it inserts a total of 8 elements if using SwissTable, now the map is composed of two buckets; this invalidates our optimization when the number of buckets is 1 in map_faststr.go. We can also observe a similar case in MapFirst, where there is a significant performance change when the number of buckets changes. Some of these problems may be solved by adding special optimizations, such as growing the capacity after the first bucket is full.
We removed some optimizations to avoid a CL containing many changes, such as
- Store bucketmask instead of B. So that we don't need to calculate the bucketmask every time, it can save about 0.3ns each time, about 10% improvement for some benchmarks that consume less time.
- Remove the overflow pointer in the bucket. It will help the overall performance and GC.

Is incremental rehashing something that can be done and just hasn't been implemented yet, or is it fundamentally difficult?

I think it is fundamentally difficult since a single empty slot in SwissTable can break the search process(https://faultlore.com/blah/hashbrown-tldr/#deletion).

If it's fundamentally difficult to do directly in SwissTable, I've been kickaround the the idea of adopting aspects of extendible hashing for a while, which could be a general solution to incremental resizing. I should probably just file an "idea" issue about this, but I'll try to lay it out here.

That sounds like a great idea! I'll think about this idea carefully later.
We plan to internally deploy this change to some latency-sensitive services to observe the impact. If there is a significant impact on the latency, we will also consider using different ways to solve it if possible.

beoran · 2022-09-05T13:08:24Z

I like to use small maps for many purposes, so it worries me a bit that SwissTable seems to perform worse for them. Maybe a special case is needed for small maps?

zhangyunhao116 · 2022-09-06T10:24:01Z

Maybe a special case is needed for small maps?

Yes, but it may have to consider carefully(optimizing the small map may cause performance impact in other situations).

SwissTable does not always cause worse performance for small maps, and we can see the cases in the benchmark(e.g., in most key miss scenarios, the performance improves instead). Could you please tell me the cases where the small maps are often used?

Some of the slowdowns in the benchmarks can be fixed. PatchSet 10 should fix the slowdown of Pop in the runtime benchmark. I will update the benchmark result later :)

beoran · 2022-09-06T10:27:29Z

Well I use small maps often in stead of case statements, or for mapping a few input file names to processors, or for lookups such as os.Substitute can do. I am looking forward to the improved results.

aclements · 2022-09-07T16:38:42Z

Thanks for the detailed breakdown of the performance losses! My take is that there are two things that need to happen on that front:

Work on improving the small map case. I'm okay with some slowdown here, but I also think these are common enough that it's worth some effort to improve.
Optionally, improve the runtime's map benchmarks. It seems like we just don't have great benchmarks. :) We should continue to cover the small map case, though. If I'm interpreting the names of the benchmarks from your suite correctly, it looks like you are covering small maps.

You mentioned that SwissTable is better for the "miss" case than the "hit" case. If I understand your layout correctly (I haven't looked closely), you're already packing the tophash and the data together, so you'd expect one cache miss for a hit. Is that right? Does the SIMD version of SwissTable level the field between the hit and miss cases at all?

aclements · 2022-09-07T16:52:34Z

Stepping back, I think there are three high-level potential concerns to address with this:

Incremental resizing. We've already been discussing this above. :)

DoS prevention. Currently, Go maps have fairly strong denial-of-service properties. The main concern is if an attacker can control the placement of items to induce collisions, leading to n^2 behavior. Having a good, per-map seed that is factored into the hash computation (not just combined at the end) goes a long way toward preventing this. Beyond this, the concern becomes leaking too much information about long-lived maps such that an attacker could reconstruct the seed. Having non-deterministic iteration order helps a lot here. A third problem is that copying elements one-by-one from one map into another, newly allocated map can easily go n^2, but having a per-map seed also mitigates that. I think all of these mechanisms are still in place in your implementation, but wanted to confirm that.

SIMD, specifically how to actually use SIMD instructions in the map implementation. The most straightforward approach is to write the SIMD bits in assembly, but that has significant maintainability problems and may even perform worse because of the cost of transitioning to and from assembly. So, that suggests adding compiler intrinsics. General SIMD intrinsics are a wide-open area right now and I don't think we want to block the map implementation on solving that problem. :) A lot of proposals have floated around (admittedly, some of which have not been published). We could start trying them out just in the runtime. Or, if I understand correctly, SwissTable doesn't need very many or any particularly fancy SIMD operations, so maybe we just hack in some intrinsics (which we could use as a starting point for more general exploration).

CAFxX · 2022-09-08T05:51:41Z

The main concern is if an attacker can control the placement of items to induce collisions, leading to n^2 behavior. Having a good, per-map seed that is factored into the hash computation (not just combined at the end) goes a long way toward preventing this. Beyond this, the concern becomes leaking too much information about long-lived maps such that an attacker could reconstruct the seed. Having non-deterministic iteration order helps a lot here. A third problem is that copying elements one-by-one from one map into another, newly allocated map can easily go n^2, but having a per-map seed also mitigates that. I think all of these mechanisms are still in place in your implementation, but wanted to confirm that.

Another option that would help alleviate most n^2 concerns is having a per-map seed that changes when the map grows/shrinks.

josharian · 2022-09-08T08:49:16Z

a per-map seed that changes when the map grows/shrinks.

This is challenging with incremental map growth. FWIW, I believe we do opportunistically reset the seed when the length hits zero.

zhangyunhao116 · 2022-09-13T10:01:14Z

Thanks for all of the feedback :)

Work on improving the small map case.

PatchSet-11 adding the optimization of bucketmask into it, the benchmark has been improved for almost all cases(updated the benchmark result).

There are still two optimizations that can be added

Using a two-level scheme for map_fast32 and map_fast64. The idea is that we can iterate the bucket instead of using matchTopHash if iterating the bucket can have better performance. Now the threshold is 2, meaning that if 0 <= buckets <= 2, we iterate the bucket(bucket == 0 is a special case, we don't need to calculate the hash). For buckets > 2, we use the matchTopHash scheme. We can change the threshold based on the experiment, and uint32 and uint64 can have different thresholds.
Remove the overflow pointer in the bucket. ~~I have encountered some problems due to memory overlap, which is still a work in progress.~~ It has been added in PatchSet 12.

Improving the runtime's map benchmarks.

Indeed. We can add some new benchmarks to it. I feel like adding the new one into https://github.com/zhangyunhao116/gomapbench first and then migrating some of it into the runtime is a good idea.

DoS prevention.

Yes! All of these mechanisms are still in the current implementation, including the non-deterministic iteration and resetting the map's seed when the length hits zero.

SIMD

We planned to write the SIMD directly in assembly, but the experiments outside the runtime show that their performance is almost the same. I wonder if we can use ABIInternal can make the assembly run faster?

I think SIMD intrinsics is a great idea! Agree that we can start trying SIMD intrinsics just in the runtime. After some basic optimizations are done, I will start to implement the SIMD version :) Most SIMD in the SwissTable is not very tricky except the prepareSameSizeGrow, and this function is rarely called(only used in sameSizeGrow).

zhangyunhao116 · 2022-09-14T09:58:29Z

Another challenge of SIMD is that its default bucket size is 16(the basic version is 8, which is the same as before), which means memory consumption may increase significantly in some cases.

aclements · 2022-09-19T21:07:54Z

Indeed. We can add some new benchmarks to it. I feel like adding the new one into https://github.com/zhangyunhao116/gomapbench first and then migrating some of it into the runtime is a good idea.

Sounds good. Possibly we should fold your package into bent, so they run as part of the performance dashboard.

Yes! All of these mechanisms are still in the current implementation, including the non-deterministic iteration and resetting the map's seed when the length hits zero.

Perfect!

We planned to write the SIMD directly in assembly, but the experiments outside the runtime show that their performance is almost the same. I wonder if we can use ABIInternal can make the assembly run faster?

Yeah, this doesn't surprise me if you're jumping to assembly just to run a few instructions. ABIInternal would certainly improve that, since it would probably allow the entire call to be registerized. I'm not sure exactly what operations you need, but if they're taking or returning vector values there's still going to be some overhead since ABIInternal doesn't know anything about passing vector registers.

I'm not sure how much effort it is to add a few one-off SIMD intrinsics. You just need SSE, right, not AVX? The operations themselves are probably not hard to add. The register allocator already knows about the XMM registers, but only as non-vector 64-bit floating-point. That mostly shouldn't matter unless it decides to spill one (thanks @cherrymui for pointing that out). If you need AVX, things may get a lot more complicated, or maybe not since the YMM registers are just aliased onto the XMM registers, so we would just call them X registers anyway.

Another challenge of SIMD is that its default bucket size is 16(the basic version is 8, which is the same as before), which means memory consumption may increase significantly in some cases.

It's hard to say how concerning this is. Sure, if an application has a huge number of small maps, perhaps with large key or value types (though they can't go over 128 bytes each), this could add up to a lot. But the relative overhead of this decreases as map size increases. I'll see if we can get some data on this.

Are you considering the trick described in this video, where you need to allocate 16 bytes of control (or a little more for unaligned groups) but the actual bucket array can be smaller? The net result of that might actually be that the tables would be smaller than current tables.

josharian · 2022-09-19T21:18:21Z

This is exciting, but before going too far down the optimization path, it seems to me it’d be good to figure out incremental growth, as that could be a dealbreaker.

aclements · 2022-09-19T21:25:38Z

I asked @mcy for useful references to learn more about SwissTables and he pointed me to these:

Matt Kulukundis's CppCon 2017 talk is a good overview. It also has some nice insights on benchmarking. @zhangyunhao116 's top post pointed to this, and I can confirm it's worth watching. :)
Matt Kulukundis's CppCon 2019 talk gives various updates. In particular, overlapping groups and small table optimizations. A lot of this talk is specific to C++ issues.
The comments in the Abseil header describe the design and implementation in quite a bit of detail. (This is much better than Abseil's "design doc".)

aclements · 2022-09-19T21:29:25Z

I totally agree with @josharian . Making sure there's a workable incremental growth story is higher priority than SIMD optimizations.

or a little more for unaligned groups

I have not had a chance to look closely at your code yet, but I just realized you mentioned interleaving the control bytes and the values, so you must be using aligned groups. De-interleaving them may be worth exploring, but again incremental growth is more important to figure out.

thepudds · 2022-09-20T03:24:22Z

Hi there, this is indeed quite exciting!

Two other references I found useful:

This thread here, where the authors of Swisstable compare notes with the authors of the related Facebook Folly F14.
A related C++ hashtable-benchmarks repo comparing Swisstable, F14, and some others.
- The numbers are somewhat artificially improved because it bypasses the hashing of values to focus on the performance of the different containers.

(My possibly incorrect understanding of the history is the Facebook team was inspired by the 2017 CppCon Swisstable talk, but before any Swisstable code was released to the public, the Facebook team implemented their own version of the core idea along with some different tradeoffs. One difference of interest might be the recommended F14FastMap variant that based on entry size chooses between values inline vs. values packed in a contiguous array).

Also, FWIW, I had an older rough Swisstable implemented outside the runtime that used SSE for the 16-way probing, but which did not support incremental growth.

Inspired by this issue here, I dusted it off recently and I am attempting to add incremental growth. I have a sketch of how it could work, but it is a bit subtle, so before adding too much noise here, I am trying to implement at least a first cut of incremental growth. I will hopefully post more details here within a few days (which might be "whoops, sorry, flawed idea").

Finally, just to be clear, what I am doing is a simple prototype. I don't want to derail any work on the current CLs, and I would be more than happy for the talented team at ByteDance to be the ones to make something real in the runtime. ;-)

zhangyunhao116 · 2022-09-26T12:00:18Z

You just need SSE, right, not AVX?

Yes, we only need the SSE2 actually, the AVX2(including SSE3) doesn't faster than SSE2 in our tests, but it is a platform-related case, it could be different if we have different CPUs.

Are you considering the trick described in this video, where you need to allocate 16 bytes of control (or a little more for unaligned groups) but the actual bucket array can be smaller?

We don't need this trick yet :) Since the current implementation puts the tophash array and the key/value pairs in the same bucket as before. If we can put all the tophash as a separate field in the future(the plan in the TODOs), I'm happy to add this optimization.

Making sure there's a workable incremental growth story is higher priority than SIMD optimizations.

Agree! I'm benchmarking the SwissTable to see the impact of the growing mode now. The main concern I have for the incremental growth is its overhead, we need a fast algorithm. I will try to implement it later :)

thepudds · 2022-10-06T16:38:17Z

Hi there. A quick update is that I did change my older swisstable implementation at thepudds/swisstable to do incremental growth without invalidating iterators. It hopefully preserves the semantics of the runtime map.

There may still be bugs of course, but there are some tests, along with some fun fuzzing that creates coverage-guided permutations of calling sequences & arguments (via fzgen.Chain) in a self-validating map that attempts to track for example whether or not the same key is allowed to be emitted twice during a range operations based on the history of that key (e.g., a sample interesting sequence generated by the fuzzer might be: populate a map, add key X, start iteration, add key Y to trigger growth, delete X, then re-add X, finish iteration).

The performance results seem promising so far. I will post some benchmark results shortly.

Overall, I suspect some flavor of swisstable implementation in the runtime would be a nice win.

The short version of the iterator approach is:

Evacuation status is maintained during growth in a separate growth status slice. (This growth status slice uses memory, but it is not per element bur rather per group info, and it uses less than the memory overhead of the overflow buckets used by the current runtime map, even for small keys).
Iterators hold on to references to the current table and an immutable-during-growth old table. (The runtime iterators also hold on to references to tables, but the runtime's old buckets are not immutable).
Iterators walk both the old and current tables, with de-duplication to avoid emitting the same key twice and checking the live tables when needed to emit the golden data. It has some logic to avoid some hashing while doing this, and I think it does less overall hashing during mid-move iteration than the runtime map iterator (but need to confirm the hashing frequency vs. the runtime a bit more).

There are almost certainly better approaches, but this is one example of swisstables respecting the current Go map semantics with incremental resize.

thepudds · 2022-10-06T18:44:11Z

Here are some benchmark results for thepudds/swisstable. These are all for int64 keys/values. The sub-benchmark names are the count of elements in a map. Fill factor is lower than the C++ implementation to match the runtime map fill factor, mainly to make comparisons easier.

Benchmark Results

old is the runtime map, new is this swisstable implementation.
-
name                      old time/op    new time/op    delta
FillGrow/664-4            63.3µs ± 1%    58.9µs ± 2%   -6.87%  (p=0.000 n=20+20)
FillGrow/999-4             112µs ± 3%     105µs ± 2%   -5.77%  (p=0.000 n=20+20)
FillGrow/681575-4          141ms ± 4%     111ms ± 3%  -21.37%  (p=0.000 n=20+19)
FillGrow/1022362-4         262ms ± 4%     207ms ± 4%  -20.95%  (p=0.000 n=20+20)
FillGrow/5452596-4         1.51s ± 5%     1.24s ± 4%  -17.81%  (p=0.000 n=18+19)
FillGrow/8178894-4         2.72s ± 3%     2.22s ± 2%  -18.54%  (p=0.000 n=20+18)
FillPresize/664-4         29.3µs ± 2%    22.5µs ± 3%  -23.22%  (p=0.000 n=20+20)
FillPresize/999-4         45.0µs ± 4%    36.8µs ± 4%  -18.12%  (p=0.000 n=20+20)
FillPresize/681575-4      80.6ms ± 7%    66.1ms ± 7%  -17.93%  (p=0.000 n=20+20)
FillPresize/1022362-4      117ms ± 5%     122ms ± 6%   +4.54%  (p=0.000 n=20+20)
FillPresize/5452596-4      761ms ±15%     866ms ± 3%  +13.80%  (p=0.000 n=19+20)
FillPresize/8178894-4      1.12s ± 7%     1.43s ± 4%  +27.42%  (p=0.000 n=20+20)
GetHitHot/664-4           20.7µs ±15%    16.3µs ±12%  -21.28%  (p=0.000u n=20+18)
GetHitHot/999-4           19.5µs ±15%    16.5µs ± 9%  -15.62%  (p=0.000 n=20+19)
GetHitHot/681575-4        21.5µs ± 8%    17.8µs ±11%  -17.44%  (p=0.000 n=20+20)
GetHitHot/1022362-4       19.8µs ±11%    16.7µs ±11%  -15.32%  (p=0.000 n=19+19)
GetHitHot/5452596-4       21.4µs ±13%    17.0µs ±10%  -20.66%  (p=0.000 n=20+19)
GetHitHot/8178894-4       19.8µs ±17%    17.0µs ± 9%  -14.04%  (p=0.000 n=20+20)
GetMissHot/664-4          17.2µs ±23%    21.6µs ±19%  +25.54%  (p=0.000 n=20+20)
GetMissHot/999-4          15.7µs ±12%    20.2µs ±13%  +28.61%  (p=0.000 n=20+20)
GetMissHot/681575-4       17.7µs ±20%    22.6µs ±23%  +27.68%  (p=0.000 n=20+20)
GetMissHot/1022362-4      15.5µs ± 5%    19.6µs ±10%  +26.30%  (p=0.000 n=20+18)
GetMissHot/5452596-4      17.8µs ±12%    20.9µs ±19%  +17.80%  (p=0.000 n=20+19)
GetMissHot/8178894-4      15.3µs ± 6%    19.8µs ±11%  +28.92%  (p=0.000 n=19+20)
GetAllStartCold/664-4      1.10s ± 1%     0.87s ± 0%  -20.85%  (p=0.000 n=10+8)
GetAllStartCold/999-4      1.15s ± 1%     0.91s ± 1%  -20.34%  (p=0.000 n=10+10)
GetAllStartCold/681575-4   3.22s ± 3%     2.96s ± 1%   -8.04%  (p=0.000 n=9+10)
GetAllStartCold/1022362-4  3.25s ± 1%     3.44s ± 4%   +5.75%  (p=0.000 n=10+10)
GetAllStartCold/5452596-4  4.50s ± 2%     5.90s ± 3%  +31.27%  (p=0.000 n=10+10)
GetAllStartCold/8178894-4  4.77s ± 1%     6.82s ± 3%  +43.15%  (p=0.000 n=9+10)

Some comments on the results:

GetAllStartCold difference for larger maps might be greater cold penalty for swisstable's separate control bytes compared to the runtime map layout.
GetMissHot result here I think is probably not because of probing at these particular sizes (though that might be a factor at different sizes). Instead, it might be at least in part due to two transitions between Go/asm for a miss -- first transition to look for a match, then second transition to look for the presence of EMPTY slots. A typical hit in contrast only does the first Go/asm transition. (One improvement could be to have a version of the ASM that does both operations in a single transition).

Those seem promising, including this is not a fully optimized implementation (for example, no real attempt to eliminate bounds and shift checks, the Go/asm interface is heavier weight than it needs to be, there is some code reuse for convenience but that causes some unneeded work, and so on).

This is also comparing thepudds/swisstable to mapaccess2_fast64, which takes some shortcuts (e.g., in some cases skipping comparing topHash if comparing the values is faster).

On the other hand, these are only preliminary results, and this implementation ignores some corner cases like NaNs and -0.0 vs +0.0, which at least has the potential to slow things down.

This next benchmark replicates #51410 (though with a larger table to make the pattern clearer), and is the only benchmark here with strings. This is a case of a map getting "stuck" mid-growth, which then slows down iteration. Note that the runtime map and this swisstable implementation have opposite best/worst cases for the percentage of the map in mid-growth evacuation, which are called out in the comments.

Mid-move Iterator Benchmark Results

name                     time/op
RangeString_Swiss/414    2.80µs ± 4%
RangeString_Swiss/415    2.84µs ± 3%
RangeString_Swiss/416    2.82µs ± 4%
RangeString_Swiss/417    5.06µs ± 5% // best mid-move evac % for this implementation
RangeString_Swiss/418    5.61µs ± 6%
RangeString_Swiss/419    6.79µs ± 2%
[...]                  
RangeString_Swiss/445    28.4µs ± 3%
RangeString_Swiss/446    29.2µs ± 2%
RangeString_Swiss/447    30.3µs ± 3% // worst mid-move evac % for this implementation
RangeString_Swiss/448    4.30µs ± 1%
RangeString_Swiss/449    4.27µs ± 1%
-
name                     time/op
RangeString_Std/414      5.77µs ± 3%
RangeString_Std/415      5.76µs ± 4%
RangeString_Std/416      5.86µs ± 6%
RangeString_Std/417      36.6µs ± 2%  // worst mid-move evac % for stdlib map
RangeString_Std/418      35.8µs ± 3%
RangeString_Std/419      34.7µs ± 2%
RangeString_Std/420      34.0µs ± 2%
RangeString_Std/421      33.2µs ± 2%
[...]

For those mid-move iteration results, one caveat is the current iteration benchmark might not yet be a fair enough apples-to-apples comparision, including I need to tweak the swisstable calling sequence for iteration to better match the runtime map approach.

Next steps include doing a sweep over a finer-grained set of element counts, as well as smaller and larger table sizes. I think it naturally supports the memory optimization from the later C++ swisstable for small table sizes, but not yet attempted.

I had a few different sketches of how incremental growth could work, but this was a less complex approach compared to some of the other sketches. Part of the reason for this approach is also that aspirationally I'd like to try a simple or even simplistic "throw some atomics" at it, including because part of the appeal of doing growth work when reading is the nice attribute that growth penalties are then short-lived or not forever, which might open up some tradeoffs on the growth approach.

zhangyunhao116 · 2022-10-24T08:01:13Z

@thepudds Thanks! The github.com/thepudds/swisstable is a nice approach! Agree that we need a simple way to implement it.

I'm considering using a mechanism similar to the original hashmap(also like the thepudds/swisstable, but convert the fixedTable to buckets, for small map, it requires less memory, since we don't need extra headers for each map), do the incremental rehash if we need to resize the hashmap. It looks like a workable plan, and the simplest way for now.

We need to modify some features of the SwissTable:

We need a special sentinel to represent an evacuated bucket. The SwissTable C++ implementation's kSentinel looks like a good example.

They may be some differences compared to the original hashmap:

SwissTable evacuates a bucket chain instead of one bucket with its overflow buckets. For SwissTable, says we have an item that should be in bucket A, but in fact, it could be in every bucket probing from bucket A until we can find an empty slot. In most cases, the length of the bucket chain is less than 2, most for 1.

Here is a simple benchmark: SwissTable(without incremental rehash) VS hashmap(Go1.19)
(It makes me think that incremental rehash is a necessary mechanism for some latency-sensitive servers.)

zhangyunhao116 · 2022-11-11T09:51:27Z

After some explorations, I think the mechanism used by the original hashmap is not a workable plan for SwissTable. The key problem is that, in the original hashmap, we can use evacuatedX and evacuatedY to make sure that we iterate an item only once if the hash isn't repeatable(it is based on the rule that an old bucket expands to 2 buckets in the new buckets).

For SwissTable, we can't ensure that an oldbucket expands to 2 buckets during the growth, actually, an item can go to any slot in the new buckets using triangular probing. This case breaks the compatibility.

I will try other approaches, extendible hashing is a good plan, but it still requires some time to verify and implement :)

thepudds · 2023-03-03T17:06:54Z

I will try other approaches, extendible hashing is a good plan, but it still requires some time to verify and implement :)

Hi @zhangyunhao116, I'm curious if you have had time to work on this? As of November it sounded like you were thinking about going a different direction than the initial SwissTable CL you had sent, including due to the constraints of the current runtime map around incremental resizing and iterator invalidation and so on.

I'm tempted to try to put together a CL following a couple of the prototype approaches from thepudds/swisstable. I might see a plausible path to success, including respecting the current constraints of the runtime map while still getting good performance.

However, I don't want to duplicate work or step on any toes if you are still working on this or were planning on returning to it soon?

And of course, I'm not 100% sure of success, including maybe the performance ends up not being compelling enough, and I need to flesh things out more including probably changing the layout and more extensive performance testing and so on, but I've been holding off spending time on it in part because I wanted to see what happened here, as well as to explicitly check what you thought about me trying something.

Finally, thanks again for moving this forward!!

zhangyunhao116 · 2023-03-07T09:24:16Z

Hi @thepudds , feel free to send a CL if you have a workable idea on this :)

On the way to implementing this feature, I'm still considering the necessity, because it will make the SwissTable become more complicated and hard to verify its correctness. And I'm still not sure if some services in the real world require this feature (or in some rare cases, using the SIMD can solve the problem?).

These days I'm trying to use the SwissTable in our company services. The SwissTable implementation works well for simple situations like binary tools and RPC servers. The main task, for me now, is to verify its correctness, performance improvement, and corner cases. The extra abstraction from the incremental growth will probably cause performance degradation, especially for the small map.

We still need to collect more feedback from the service owners (from other teams in our company) to see the impact of immediately growing and whether or not some services need this feature.

If we think this feature is necessary for some of our internal services, I will continue to work on it. The feedback collection stage may last about 1 ~ 2 months, and I will update some information on this issue :)

rip-create-your-account · 2023-05-02T21:23:35Z

Hey! I had a use case of inserting millions of key-value pairs into a hashmap with only a relatively small amount of look-ups. I had prior experience with extendible hashing and so I implemented a new extendible hashing hashmap tuned for insertion speed in huge maps. I'm not well studied on hashmaps so beware - I basically just winged it and somehow I feel that there's a fatal flaw somewhere. My software and tests works just fine so I dunno.

Inserting 100 * 1000 * 1000 [int64, int64] key-value pairs to it takes ~13s while for the built-in map it takes ~19s. Also the built-in map uses 2x the amount of physical memory. That particular implementation I specialized to my use case so all hashmaps had a fixed amount 64 buckets and each bucket had 8 key-value pairs.

Motivated by the insertion performance and the reduced memory overhead I modified it to use dynamic amount of buckets so that small maps don't waste memory. See this gist for that hastily modified version of my original implementation. Note that this dynamic version is almost 2x slower for my use case when it comes to inserting and look-ups. Also note that only Put and Get are implemented in a mostly proper manner. No random iteration order, no shrinking after Delete, etc etc etc. In my gist implementation Put has competitive performance against the built-in map but Get and Delete fail somewhat.

A few interesting aspects about it that I want to point out:

By storing additional 8 bits of the hash value (triehash8) per key-value pair we get to grow the size of the map 8 times without having to recalculate the full hash for the keys. See the split() function for that where the 8 bits are used to split the key-value pairs correctly to the two maps. These 8 bits can also be used during probing to reduce false positives when matching hashes. Very useful property when your keys are long strings.
In my original implementation all hashmaps had 64 buckets each. In the gist version I start with 1 bucket and after a few splits I start doubling the amount of buckets per hashmap until they grow up to 64 buckets. 64 buckets because it got me the best insert performance. So when inserting the 9th key-value pair a new hashmap with 1 bucket is allocated and ~half of the key-value pairs from the first map are moved to it. In total there's 8+8 slots between the two maps and so we got our doubling in size.
Growing produces hardly any garbage for the GC to collect if implemented properly. If the hashmap that is being split is reused then there is nothing left behind to collect (if we don't allocate more buckets for the hashmap). Gist does not do this. Iterating could mess up this plan though.
All around interesting behaviour when it comes to CPU caches. Growth doesn't pollute the cache with the totality of the old and new map, lookup has some additional cache-miss spots, etc etc.
The hashmap can be limited to mostly make only ~smallish allocations and I would assume that it would help the allocator/GC in mysterious ways when all of the hashmaps in the software makes allocations of roughly the same size. The BenchmarkShortUse in main_test.go kind of tries to showcase this and it has really interesting results when multiple CPU cores are available to the Go runtime (works on my machine).

It would be nice to have someone with a wrinkly brain have a go at extendible hashing, perhaps with a SwissTable in the insides. All the literature that I find on extendible hashing (outside of database stuff) is very surface level and my search engine only brought me to this issue. Thank you for visiting my blog.

*** Next up: Visit a cleaned up version of it here.

gopherbot added the compiler/runtime Issues related to the Go compiler and/or runtime. label Aug 30, 2022

seankhliao added the NeedsInvestigation Someone must examine and confirm this is a valid issue and not a duplicate of an existing one. label Aug 30, 2022

egonelbre mentioned this issue Aug 30, 2022

sync: improve Map performance with lock free list #54720

Open

marco-m-pix4d mentioned this issue Aug 31, 2022

add a generic set data structure Pix4D/cogito#99

Merged

mknyszek added this to the Unplanned milestone Aug 31, 2022

mknyszek assigned zhangyunhao116 Aug 31, 2022

thepudds mentioned this issue Oct 21, 2022

spec: add clear(x) builtin, to clear map, zero content of slice #56351

Closed

dsnet mentioned this issue Apr 26, 2023

suggestions about its performance / additon to the benchmarks go-json-experiment/json#8

Open

runtime: use SwissTable #54766

runtime: use SwissTable #54766

zhangyunhao116 commented Aug 30, 2022 •

edited

zhangyunhao116 commented Aug 30, 2022 •

edited

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zhangyunhao116 commented Sep 6, 2022 •

edited

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zhangyunhao116 commented Sep 13, 2022 •

edited

zhangyunhao116 commented Sep 14, 2022

aclements commented Sep 19, 2022

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aclements commented Sep 19, 2022

aclements commented Sep 19, 2022

thepudds commented Sep 20, 2022

zhangyunhao116 commented Sep 26, 2022

thepudds commented Oct 6, 2022 •

edited

thepudds commented Oct 6, 2022 •

edited

zhangyunhao116 commented Oct 24, 2022

zhangyunhao116 commented Nov 11, 2022

thepudds commented Mar 3, 2023

zhangyunhao116 commented Mar 7, 2023 •

edited

rip-create-your-account commented May 2, 2023 •

edited

runtime: use SwissTable #54766

runtime: use SwissTable #54766

Comments

zhangyunhao116 commented Aug 30, 2022 • edited

Abstract

Motivations

Implementations

Tasks

Advantages compared to the original implementation

Disadvantages compared to the original implementation

Implementation details

Differences with SwissTable

Differences with the original implementation

References

zhangyunhao116 commented Aug 30, 2022 • edited

Performance comparison

Platform

Benchmark-1

Benchmark-2

gopherbot commented Aug 30, 2022

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prattmic commented Aug 30, 2022

aaronbee commented Aug 30, 2022

aaronbee commented Aug 30, 2022

randall77 commented Aug 30, 2022

aclements commented Aug 31, 2022

mknyszek commented Aug 31, 2022

zhangyunhao116 commented Sep 2, 2022

beoran commented Sep 5, 2022

zhangyunhao116 commented Sep 6, 2022 • edited

beoran commented Sep 6, 2022

aclements commented Sep 7, 2022

aclements commented Sep 7, 2022

CAFxX commented Sep 8, 2022

josharian commented Sep 8, 2022

zhangyunhao116 commented Sep 13, 2022 • edited

zhangyunhao116 commented Sep 14, 2022

aclements commented Sep 19, 2022

josharian commented Sep 19, 2022

aclements commented Sep 19, 2022

aclements commented Sep 19, 2022

thepudds commented Sep 20, 2022

zhangyunhao116 commented Sep 26, 2022

thepudds commented Oct 6, 2022 • edited

thepudds commented Oct 6, 2022 • edited

zhangyunhao116 commented Oct 24, 2022

zhangyunhao116 commented Nov 11, 2022

thepudds commented Mar 3, 2023

zhangyunhao116 commented Mar 7, 2023 • edited

rip-create-your-account commented May 2, 2023 • edited

zhangyunhao116 commented Aug 30, 2022 •

edited

zhangyunhao116 commented Aug 30, 2022 •

edited

zhangyunhao116 commented Sep 6, 2022 •

edited

zhangyunhao116 commented Sep 13, 2022 •

edited

thepudds commented Oct 6, 2022 •

edited

thepudds commented Oct 6, 2022 •

edited

zhangyunhao116 commented Mar 7, 2023 •

edited

rip-create-your-account commented May 2, 2023 •

edited