1 __Zstandard__, or `zstd` as short version, is a fast lossless compression algorithm, 2 targeting real-time compression scenarios at zlib-level and better compression ratios. 3 4It is provided as an open-source BSD-licensed **C** library, 5and a command line utility producing and decoding `.zst` and `.gz` files. 6For other programming languages, 7you can consult a list of known ports on [Zstandard homepage](http://www.zstd.net/#other-languages). 8 9| dev branch status | 10|-------------------| 11| [![Build Status][travisDevBadge]][travisLink] [![Build status][AppveyorDevBadge]][AppveyorLink] [![Build status][CircleDevBadge]][CircleLink] 12 13[travisDevBadge]: https://travis-ci.org/facebook/zstd.svg?branch=dev "Continuous Integration test suite" 14[travisLink]: https://travis-ci.org/facebook/zstd 15[AppveyorDevBadge]: https://ci.appveyor.com/api/projects/status/xt38wbdxjk5mrbem/branch/dev?svg=true "Windows test suite" 16[AppveyorLink]: https://ci.appveyor.com/project/YannCollet/zstd-p0yf0 17[CircleDevBadge]: https://circleci.com/gh/facebook/zstd/tree/dev.svg?style=shield "Short test suite" 18[CircleLink]: https://circleci.com/gh/facebook/zstd 19 20 21As a reference, several fast compression algorithms were tested and compared 22on a server running Linux Debian (`Linux version 4.8.0-1-amd64`), 23with a Core i7-6700K CPU @ 4.0GHz, 24using [lzbench], an open-source in-memory benchmark by @inikep 25compiled with GCC 6.3.0, 26on the [Silesia compression corpus]. 27 28[lzbench]: https://github.com/inikep/lzbench 29[Silesia compression corpus]: http://sun.aei.polsl.pl/~sdeor/index.php?page=silesia 30 31| Compressor name | Ratio | Compression| Decompress.| 32| --------------- | ------| -----------| ---------- | 33| **zstd 1.1.3 -1** | 2.877 | 430 MB/s | 1110 MB/s | 34| zlib 1.2.8 -1 | 2.743 | 110 MB/s | 400 MB/s | 35| brotli 0.5.2 -0 | 2.708 | 400 MB/s | 430 MB/s | 36| quicklz 1.5.0 -1 | 2.238 | 550 MB/s | 710 MB/s | 37| lzo1x 2.09 -1 | 2.108 | 650 MB/s | 830 MB/s | 38| lz4 1.7.5 | 2.101 | 720 MB/s | 3600 MB/s | 39| snappy 1.1.3 | 2.091 | 500 MB/s | 1650 MB/s | 40| lzf 3.6 -1 | 2.077 | 400 MB/s | 860 MB/s | 41 42[zlib]:http://www.zlib.net/ 43[LZ4]: http://www.lz4.org/ 44 45Zstd can also offer stronger compression ratios at the cost of compression speed. 46Speed vs Compression trade-off is configurable by small increments. Decompression speed is preserved and remains roughly the same at all settings, a property shared by most LZ compression algorithms, such as [zlib] or lzma. 47 48The following tests were run 49on a server running Linux Debian (`Linux version 4.8.0-1-amd64`) 50with a Core i7-6700K CPU @ 4.0GHz, 51using [lzbench], an open-source in-memory benchmark by @inikep 52compiled with GCC 6.3.0, 53on the [Silesia compression corpus]. 54 55Compression Speed vs Ratio | Decompression Speed 56---------------------------|-------------------- 57 |  58 59Several algorithms can produce higher compression ratios, but at slower speeds, falling outside of the graph. 60For a larger picture including very slow modes, [click on this link](doc/images/DCspeed5.png) . 61 62 63### The case for Small Data compression 64 65Previous charts provide results applicable to typical file and stream scenarios (several MB). Small data comes with different perspectives. 66 67The smaller the amount of data to compress, the more difficult it is to compress. This problem is common to all compression algorithms, and reason is, compression algorithms learn from past data how to compress future data. But at the beginning of a new data set, there is no "past" to build upon. 68 69To solve this situation, Zstd offers a __training mode__, which can be used to tune the algorithm for a selected type of data. 70Training Zstandard is achieved by providing it with a few samples (one file per sample). The result of this training is stored in a file called "dictionary", which must be loaded before compression and decompression. 71Using this dictionary, the compression ratio achievable on small data improves dramatically. 72 73The following example uses the `github-users` [sample set](https://github.com/facebook/zstd/releases/tag/v1.1.3), created from [github public API](https://developer.github.com/v3/users/#get-all-users). 74It consists of roughly 10K records weighing about 1KB each. 75 76Compression Ratio | Compression Speed | Decompression Speed 77------------------|-------------------|-------------------- 78 |  |  79 80 81These compression gains are achieved while simultaneously providing _faster_ compression and decompression speeds. 82 83Training works if there is some correlation in a family of small data samples. The more data-specific a dictionary is, the more efficient it is (there is no _universal dictionary_). 84Hence, deploying one dictionary per type of data will provide the greatest benefits. 85Dictionary gains are mostly effective in the first few KB. Then, the compression algorithm will gradually use previously decoded content to better compress the rest of the file. 86 87#### Dictionary compression How To : 88 891) Create the dictionary 90 91`zstd --train FullPathToTrainingSet/* -o dictionaryName` 92 932) Compress with dictionary 94 95`zstd -D dictionaryName FILE` 96 973) Decompress with dictionary 98 99`zstd -D dictionaryName --decompress FILE.zst` 100 101 102### Build 103 104Once you have the repository cloned, there are multiple ways provided to build Zstandard. 105 106#### Makefile 107 108If your system is compatible with a standard `make` (or `gmake`) binary generator, 109you can simply run it at the root directory. 110It will generate `zstd` within root directory. 111 112Other available options include : 113- `make install` : create and install zstd binary, library and man page 114- `make test` : create and run `zstd` and test tools on local platform 115 116#### cmake 117 118A `cmake` project generator is provided within `build/cmake`. 119It can generate Makefiles or other build scripts 120to create `zstd` binary, and `libzstd` dynamic and static libraries. 121 122#### Meson 123 124A Meson project is provided within `contrib/meson`. 125 126#### Visual Studio (Windows) 127 128Going into `build` directory, you will find additional possibilities : 129- Projects for Visual Studio 2005, 2008 and 2010 130 + VS2010 project is compatible with VS2012, VS2013 and VS2015 131- Automated build scripts for Visual compiler by @KrzysFR , in `build/VS_scripts`, 132 which will build `zstd` cli and `libzstd` library without any need to open Visual Studio solution. 133 134 135### Status 136 137Zstandard is currently deployed within Facebook. It is used continuously to compress large amounts of data in multiple formats and use cases. 138Zstandard is considered safe for production environments. 139 140### License 141 142Zstandard is dual-licensed under [BSD](LICENSE) and [GPLv2](COPYING). 143 144### Contributing 145 146The "dev" branch is the one where all contributions will be merged before reaching "master". 147If you plan to propose a patch, please commit into the "dev" branch or its own feature branch. 148Direct commit to "master" are not permitted. 149For more information, please read [CONTRIBUTING](CONTRIBUTING.md). 150 151### Miscellaneous 152 153Zstd entropy stage is provided by [Huff0 and FSE, from Finite State Entropy library](https://github.com/Cyan4973/FiniteStateEntropy). 154
