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BigInteger parsing optimizations #47842

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merged 4 commits into from May 9, 2021
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jfd16
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@jfd16 jfd16 commented Feb 4, 2021

Improves performance of BigInteger parsing from decimal and hex strings (both speed and memory allocations), according to the benchmark that I have included. The difference is particularly significant for large decimal strings, given that the current implementation allocates two BigInteger instances for each input digit.

Benchmark code

using System.Collections.Generic;
using System.Globalization;
using System.Linq;
using BenchmarkDotNet.Attributes;

public class BigIntegerParseBenchmarks
{
    public IEnumerable<object> NumberStrings =>
        new string[]
        {
            "123",
            int.MinValue.ToString(),
            string.Concat(Enumerable.Repeat("1234567890", 20)),
            string.Concat(Enumerable.Repeat("654719003", 57)),
        };

    public IEnumerable<object> NumberStringsHex =>
        new string[]
        {
            "12A",
            int.MinValue.ToString("X"),
            string.Concat(Enumerable.Repeat("1234567890abcdefffff", 10)),
            string.Concat(Enumerable.Repeat("18a473f5d", 57)),
        };

    [Benchmark]
    [ArgumentsSource(nameof(NumberStrings))]
    public BigInteger Parse(string numberString) => BigInteger.Parse(numberString);

    [Benchmark]
    [ArgumentsSource(nameof(NumberStringsHex))]
    public BigInteger ParseHex(string numberString) => BigInteger.Parse(numberString, NumberStyles.HexNumber);
}

Benchmark results (on master branch)

BenchmarkDotNet=v0.12.1.1466-nightly, OS=Windows 10.0.18363.1316 (1909/November2019Update/19H2)
Intel Core i7-8550U CPU 1.80GHz (Kaby Lake R), 1 CPU, 8 logical and 4 physical cores
.NET SDK=5.0.102
  [Host]     : .NET 6.0.0 (6.0.21.10203), X64 RyuJIT
  Job-NSGODO : .NET 6.0.0 (42.42.42.42424), X64 RyuJIT

PowerPlanMode=00000000-0000-0000-0000-000000000000  Arguments=/p:DebugType=portable  Toolchain=CoreRun  
IterationTime=250.0000 ms  MaxIterationCount=20  MinIterationCount=15  
WarmupCount=1  
Method numberString Mean Error StdDev Median Min Max Gen 0 Gen 1 Gen 2 Allocated
Parse 123 186.5 ns 3.43 ns 2.87 ns 187.0 ns 181.9 ns 192.6 ns 0.0246 - - 104 B
Parse -2147483648 418.0 ns 16.69 ns 18.55 ns 419.0 ns 359.6 ns 442.6 ns 0.0312 - - 136 B
Parse 123456789012(...)901234567890 [200] 17,866.9 ns 193.43 ns 180.93 ns 17,901.3 ns 17,527.7 ns 18,163.3 ns 13.1653 - - 55,176 B
Parse 654719003654(...)003654719003 [513] 69,284.7 ns 643.04 ns 536.97 ns 69,112.3 ns 68,447.0 ns 70,545.0 ns 65.5556 - - 274,272 B
ParseHex 12A 121.8 ns 0.64 ns 0.50 ns 121.7 ns 121.3 ns 123.2 ns 0.0323 - - 136 B
ParseHex 80000000 183.5 ns 1.28 ns 1.07 ns 183.6 ns 182.4 ns 185.5 ns 0.0319 - - 136 B
ParseHex 1234567890ab(...)90abcdefffff [200] 2,520.9 ns 17.84 ns 14.90 ns 2,511.0 ns 2,505.7 ns 2,544.7 ns 0.2609 - - 1,128 B
ParseHex 18a473f5d18a(...)f5d18a473f5d [513] 6,069.5 ns 83.14 ns 77.77 ns 6,045.6 ns 5,938.0 ns 6,202.7 ns 0.7287 - - 3,128 B

Results after changes

BenchmarkDotNet=v0.12.1.1466-nightly, OS=Windows 10.0.18363.1316 (1909/November2019Update/19H2)
Intel Core i7-8550U CPU 1.80GHz (Kaby Lake R), 1 CPU, 8 logical and 4 physical cores
.NET SDK=5.0.102
  [Host]     : .NET 6.0.0 (6.0.21.10203), X64 RyuJIT
  Job-WMUKDU : .NET 6.0.0 (42.42.42.42424), X64 RyuJIT

PowerPlanMode=00000000-0000-0000-0000-000000000000  Arguments=/p:DebugType=portable  Toolchain=CoreRun  
IterationTime=250.0000 ms  MaxIterationCount=20  MinIterationCount=15  
WarmupCount=1  
Method numberString Mean Error StdDev Median Min Max Gen 0 Gen 1 Gen 2 Allocated
Parse 123 126.0 ns 1.81 ns 1.51 ns 125.8 ns 123.7 ns 128.9 ns 0.0248 - - 104 B
Parse -2147483648 176.5 ns 3.55 ns 3.65 ns 174.7 ns 171.9 ns 182.6 ns 0.0322 - - 136 B
Parse 123456789012(...)901234567890 [200] 1,843.5 ns 21.83 ns 20.42 ns 1,843.6 ns 1,819.9 ns 1,875.5 ns 0.2339 - - 984 B
Parse 654719003654(...)003654719003 [513] 5,197.3 ns 23.14 ns 20.51 ns 5,206.4 ns 5,134.6 ns 5,210.8 ns 0.6656 - - 2,792 B
ParseHex 12A 116.3 ns 1.23 ns 1.09 ns 116.2 ns 114.9 ns 118.8 ns 0.0245 - - 104 B
ParseHex 80000000 166.1 ns 1.76 ns 1.56 ns 165.9 ns 164.2 ns 169.3 ns 0.0320 - - 136 B
ParseHex 1234567890ab(...)90abcdefffff [200] 1,705.1 ns 10.51 ns 8.77 ns 1,703.0 ns 1,692.7 ns 1,715.7 ns 0.2362 - - 1,000 B
ParseHex 18a473f5d18a(...)f5d18a473f5d [513] 3,905.5 ns 34.60 ns 30.67 ns 3,907.6 ns 3,866.8 ns 3,975.6 ns 0.6660 - - 2,840 B

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Tagging subscribers to this area: @tannergooding, @pgovind
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Issue Details

Improves performance of BigInteger parsing from decimal and hex strings (both speed and memory allocations), according to the benchmark that I have included. The difference is particularly significant for large decimal strings, given that the current implementation allocates two BigInteger instances for each input digit.

Benchmark code

using System.Collections.Generic;
using System.Globalization;
using System.Linq;
using BenchmarkDotNet.Attributes;

public class BigIntegerParseBenchmarks
{
    public IEnumerable<object> NumberStrings =>
        new string[]
        {
            "123",
            int.MinValue.ToString(),
            string.Concat(Enumerable.Repeat("1234567890", 20)),
            string.Concat(Enumerable.Repeat("654719003", 57)),
        };

    public IEnumerable<object> NumberStringsHex =>
        new string[]
        {
            "12A",
            int.MinValue.ToString("X"),
            string.Concat(Enumerable.Repeat("1234567890abcdefffff", 10)),
            string.Concat(Enumerable.Repeat("18a473f5d", 57)),
        };

    [Benchmark]
    [ArgumentsSource(nameof(NumberStrings))]
    public BigInteger Parse(string numberString) => BigInteger.Parse(numberString);

    [Benchmark]
    [ArgumentsSource(nameof(NumberStringsHex))]
    public BigInteger ParseHex(string numberString) => BigInteger.Parse(numberString, NumberStyles.HexNumber);
}

Benchmark results (on master branch)

BenchmarkDotNet=v0.12.1.1466-nightly, OS=Windows 10.0.18363.1316 (1909/November2019Update/19H2)
Intel Core i7-8550U CPU 1.80GHz (Kaby Lake R), 1 CPU, 8 logical and 4 physical cores
.NET SDK=5.0.102
  [Host]     : .NET 6.0.0 (6.0.21.10203), X64 RyuJIT
  Job-NSGODO : .NET 6.0.0 (42.42.42.42424), X64 RyuJIT

PowerPlanMode=00000000-0000-0000-0000-000000000000  Arguments=/p:DebugType=portable  Toolchain=CoreRun  
IterationTime=250.0000 ms  MaxIterationCount=20  MinIterationCount=15  
WarmupCount=1  
Method numberString Mean Error StdDev Median Min Max Gen 0 Gen 1 Gen 2 Allocated
Parse 123 186.5 ns 3.43 ns 2.87 ns 187.0 ns 181.9 ns 192.6 ns 0.0246 - - 104 B
Parse -2147483648 418.0 ns 16.69 ns 18.55 ns 419.0 ns 359.6 ns 442.6 ns 0.0312 - - 136 B
Parse 123456789012(...)901234567890 [200] 17,866.9 ns 193.43 ns 180.93 ns 17,901.3 ns 17,527.7 ns 18,163.3 ns 13.1653 - - 55,176 B
Parse 654719003654(...)003654719003 [513] 69,284.7 ns 643.04 ns 536.97 ns 69,112.3 ns 68,447.0 ns 70,545.0 ns 65.5556 - - 274,272 B
ParseHex 12A 121.8 ns 0.64 ns 0.50 ns 121.7 ns 121.3 ns 123.2 ns 0.0323 - - 136 B
ParseHex 80000000 183.5 ns 1.28 ns 1.07 ns 183.6 ns 182.4 ns 185.5 ns 0.0319 - - 136 B
ParseHex 1234567890ab(...)90abcdefffff [200] 2,520.9 ns 17.84 ns 14.90 ns 2,511.0 ns 2,505.7 ns 2,544.7 ns 0.2609 - - 1,128 B
ParseHex 18a473f5d18a(...)f5d18a473f5d [513] 6,069.5 ns 83.14 ns 77.77 ns 6,045.6 ns 5,938.0 ns 6,202.7 ns 0.7287 - - 3,128 B

Results after changes

BenchmarkDotNet=v0.12.1.1466-nightly, OS=Windows 10.0.18363.1316 (1909/November2019Update/19H2)
Intel Core i7-8550U CPU 1.80GHz (Kaby Lake R), 1 CPU, 8 logical and 4 physical cores
.NET SDK=5.0.102
  [Host]     : .NET 6.0.0 (6.0.21.10203), X64 RyuJIT
  Job-WMUKDU : .NET 6.0.0 (42.42.42.42424), X64 RyuJIT

PowerPlanMode=00000000-0000-0000-0000-000000000000  Arguments=/p:DebugType=portable  Toolchain=CoreRun  
IterationTime=250.0000 ms  MaxIterationCount=20  MinIterationCount=15  
WarmupCount=1  
Method numberString Mean Error StdDev Median Min Max Gen 0 Gen 1 Gen 2 Allocated
Parse 123 126.0 ns 1.81 ns 1.51 ns 125.8 ns 123.7 ns 128.9 ns 0.0248 - - 104 B
Parse -2147483648 176.5 ns 3.55 ns 3.65 ns 174.7 ns 171.9 ns 182.6 ns 0.0322 - - 136 B
Parse 123456789012(...)901234567890 [200] 1,843.5 ns 21.83 ns 20.42 ns 1,843.6 ns 1,819.9 ns 1,875.5 ns 0.2339 - - 984 B
Parse 654719003654(...)003654719003 [513] 5,197.3 ns 23.14 ns 20.51 ns 5,206.4 ns 5,134.6 ns 5,210.8 ns 0.6656 - - 2,792 B
ParseHex 12A 116.3 ns 1.23 ns 1.09 ns 116.2 ns 114.9 ns 118.8 ns 0.0245 - - 104 B
ParseHex 80000000 166.1 ns 1.76 ns 1.56 ns 165.9 ns 164.2 ns 169.3 ns 0.0320 - - 136 B
ParseHex 1234567890ab(...)90abcdefffff [200] 1,705.1 ns 10.51 ns 8.77 ns 1,703.0 ns 1,692.7 ns 1,715.7 ns 0.2362 - - 1,000 B
ParseHex 18a473f5d18a(...)f5d18a473f5d [513] 3,905.5 ns 34.60 ns 30.67 ns 3,907.6 ns 3,866.8 ns 3,975.6 ns 0.6660 - - 2,840 B
Author: jfd16
Assignees: -
Labels:

area-System.Numerics

Milestone: -

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dnfadmin commented Feb 4, 2021

CLA assistant check
All CLA requirements met.

@danmoseley
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The use of ArrayPool is much more common than ArrayPool

Grepped under libraries/*/src/**cs for interest and I see

object - 2
IntPtr, GCHandle - 4 each
char - 118
byte - 301

there are no uses I see for int or uint.

@tannergooding
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Grepped under libraries/*/src/**cs for interest and I see

I wonder if there is something we can do here to promote better sharing. Particularly when using Span the underlying data type doesn't really matter too much (provided it has the correct alignment)

@jfd16
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jfd16 commented Feb 5, 2021

The use of ArrayPool is much more common than ArrayPool

Grepped under libraries/*/src/**cs for interest and I see

object - 2
IntPtr, GCHandle - 4 each
char - 118
byte - 301

there are no uses I see for int or uint.

ArrayPool<int> is being used indirectly in some places through ValueListBuilder: https://github.com/dotnet/runtime/search?q=ValueListBuilder+path%3Asrc

@jfd16 jfd16 force-pushed the bigint-parse-perf branch 3 times, most recently from 3041198 to 2383bd3 Compare February 9, 2021 01:42
{
char c = number.digits[i];
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@stephentoub, is this an opportunity for an analyzer? Indexing into StringBuilder can be deceptively slow due to its internal chunking.

isNegative = true;
foreach (ReadOnlyMemory<char> digitsChunkMem in number.digits.GetChunks())
{
ReadOnlySpan<char> chunkDigits = digitsChunkMem.Span;
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Likewise, I wonder if we should have a (internal for now) CurrentSpan property that is slightly more efficient.

We don't really need to return a ReadOnlyMemory when we only want to extract the underlying Span<T>, particularly when the ROM<T> is just being constructed over a backing array.

It's, in practice, no more unsafe than say CollectionsMarshal.AsSpan

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LGTM. I think it can be merged provided @stephentoub has no additional feedback

@danmoseley
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I wonder if there is something we can do here to promote better sharing. Particularly when using Span the underlying data type doesn't really matter too much (provided it has the correct alignment

Worth an issue do you think @tannergooding

Base automatically changed from master to main March 1, 2021 09:07
@jeffhandley
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/azp run runtime

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@jeffhandley jeffhandley merged commit b3278ca into dotnet:main May 9, 2021
@karelz karelz added this to the 6.0.0 milestone May 20, 2021
@jfd16 jfd16 deleted the bigint-parse-perf branch May 21, 2021 04:16
@jfd16 jfd16 restored the bigint-parse-perf branch June 16, 2021 02:12
@msftbot msftbot bot locked as resolved and limited conversation to collaborators Jul 16, 2021
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7 participants