A high-performance, concurrent hash table
C++ M4 Other
Latest commit 96ec0e7 Sep 12, 2016 @manugoyal manugoyal Removed SECTION from user exceptions test
Catch is not exactly thread safe, so it was breaking on some machines.


Note to existing users: the iterator implementation has changed significantly since we introduced the locked_table in this commit. Please see the locked_table documentation and examples directory for information and examples of how to use iterators.


libcuckoo provides a high-performance, compact hash table that allows multiple concurrent reader and writer threads.

The Doxygen-generated documentation is available at the project page.

Authors: Manu Goyal, Bin Fan, Xiaozhou Li, David G. Andersen, and Michael Kaminsky

For details about this algorithm and citations, please refer to our papers in NSDI 2013 and EuroSys 2014. Some of the details of the hashing algorithm have been improved since that work (e.g., the previous algorithm in 1 serializes all writer threads, while our current implementation supports multiple concurrent writers), however, and this source code is now the definitive reference.


This library has been tested on Mac OSX >= 10.8 and Ubuntu >= 12.04.

It compiles with clang++ >= 3.3 and g++ >= 4.7, however we strongly suggest using the latest versions of both compilers, as they have greatly improved support for atomic operations. Building the library requires the autotools. Install them on Ubuntu

$ sudo apt-get update && sudo apt-get install build-essential autoconf libtool


$ autoreconf -fis
$ ./configure
$ make
$ make install


To build a program with the hash table, include libcuckoo/cuckoohash_map.hh into your source file. If you want to use CityHash, which we recommend, we have provided a wrapper compatible with the std::hash type around it in the libcuckoo/city_hasher.hh file. If compiling with CityHash, add the -lcityhash flag. You must also enable C++11 features on your compiler. Compiling the file examples/count_freq.cc with g++ might look like this:

$ g++ -std=c++11 examples/count_freq.cc -lcityhash

The examples directory contains some simple demonstrations of some of the basic features of the hash table.


The tests directory directory contains a number of tests and benchmarks of the hash table, which also can serve as useful examples of how to use the table's various features. After running make all, the entire test suite can be run with the make check command. This will not run the benchmarks, which must be run individually. The test executables, which have the suffix .out, can be run individually as well.

Issue Report

To let us know your questions or issues, we recommend you report an issue on github. You can also email us at libcuckoo-dev@googlegroups.com.


Copyright (C) 2013, Carnegie Mellon University and Intel Corporation

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at


Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.

CityHash (lib/city.h, lib/city.cc) is Copyright (c) Google, Inc. and has its own license, as detailed in the source files.