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Nick Terrell 54c4babd8f Always check Huffman tables for ZSTD_lazy+ 
The compressor always reuses the existing Huffman table if the literals
size is at most 1 KiB. If the compression strategy is `ZSTD_lazy` or
stronger always check to see if reusing the previous table or creating
a new table is better.

This doesn't yet weigh in decompression speed. I don't want to add any
heuristics there until I have real data to work with to ensure that the
heuristic works for at least one use case, preferably more.
2017-03-03 16:49:38 -08:00
build Added compile flags to pzstd 2017-02-28 10:57:09 +01:00
contrib Merge branch 'dev' into doc 2017-02-23 15:23:24 -08:00
doc zstdmt : fix : loading prefix from previous segments 2017-02-23 23:42:12 -08:00
examples fixed malloc(0) potential issue 2017-02-22 11:08:00 -08:00
lib Always check Huffman tables for ZSTD_lazy+ 2017-03-03 16:49:38 -08:00
programs fixed : build zstd cli after libzstd 2017-03-01 21:02:06 -08:00
tests make : added target shortest 2017-03-01 17:02:49 -08:00
zlibWrapper zlibWrapper: better description of ZWRAP_useZSTDcompression 2017-02-23 18:28:48 +01:00
.buckconfig Add BUCK files for Nuclide support 2017-01-27 10:43:12 -08:00
.buckversion Add BUCK files for Nuclide support 2017-01-27 10:43:12 -08:00
.gitattributes zstd.exe has FileVersion and ProductVersion 2016-09-13 13:53:43 +02:00
.gitignore Add BUCK files for Nuclide support 2017-01-27 10:43:12 -08:00
.travis.yml travis.yml: fixed pull_request 2017-02-28 18:34:39 +01:00
appveyor.yml appveyor.yml: fixed clang test 2017-02-10 13:10:25 +01:00
circle.yml Create a tool that generates random, valid, Zstd frames for decoder testing 2017-02-22 16:08:34 -08:00
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README.md Fix for a small Typo 2017-02-27 16:28:22 +05:30

README.md

Zstandard, or zstd as short version, is a fast lossless compression algorithm, targeting real-time compression scenarios at zlib-level and better compression ratios.

It is provided as an open-source BSD-licensed C library, and a command line utility producing and decoding .zst and .gz files. For other programming languages, you can consult a list of known ports on Zstandard homepage.

Branch Status
master Build Status
dev Build Status

As a reference, several fast compression algorithms were tested and compared on a Core i7-3930K CPU @ 4.5GHz, using lzbench, an open-source in-memory benchmark by @inikep compiled with GCC 5.4.0, with the Silesia compression corpus.

Name Ratio C.speed D.speed
MB/s MB/s
zstd 0.8.2 -1 2.877 330 940
zlib 1.2.8 deflate -1 2.730 95 360
brotli 0.4 -0 2.708 320 375
QuickLZ 1.5 2.237 510 605
LZO 2.09 2.106 610 870
LZ4 r131 2.101 620 3100
Snappy 1.1.3 2.091 480 1600
LZF 3.6 2.077 375 790

Zstd can also offer stronger compression ratios at the cost of compression speed. Speed 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.

The following tests were run on a Core i7-3930K CPU @ 4.5GHz, using lzbench, an open-source in-memory benchmark by @inikep compiled with GCC 5.2.1, on the Silesia compression corpus.

Compression Speed vs Ratio Decompression Speed
Compression Speed vs Ratio Decompression Speed

Several algorithms can produce higher compression ratios, but at slower speeds, falling outside of the graph. For a larger picture including very slow modes, click on this link .

The case for Small Data compression

Previous charts provide results applicable to typical file and stream scenarios (several MB). Small data comes with different perspectives.

The 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.

To solve this situation, Zstd offers a training mode, which can be used to tune the algorithm for a selected type of data. Training Zstandard is achieved by provide 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. Using this dictionary, the compression ratio achievable on small data improves dramatically.

The following example uses the github-users sample set, created from github public API. It consists of roughly 10K records weighting about 1KB each.

Compression Ratio Compression Speed Decompression Speed
Compression Ratio Compression Speed Decompression Speed

These compression gains are achieved while simultaneously providing faster compression and decompression speeds.

Training 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). Hence, deploying one dictionary per type of data will provide the greatest benefits. Dictionary 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.

Dictionary compression How To :

  1. Create the dictionary

zstd --train FullPathToTrainingSet/* -o dictionaryName

  1. Compress with dictionary

zstd -D dictionaryName FILE

  1. Decompress with dictionary

zstd -D dictionaryName --decompress FILE.zst

Build

Once you have the repository cloned, there are multiple ways provided to build Zstandard.

Makefile

If your system is compatible with a standard make (or gmake) binary generator, you can simply run it at the root directory. It will generate zstd within root directory.

Other available options include :

  • make install : create and install zstd binary, library and man page
  • make test : create and run zstd and test tools on local platform

cmake

A cmake project generator is provided within build/cmake. It can generate Makefiles or other build scripts to create zstd binary, and libzstd dynamic and static libraries.

Meson

A Meson project is provided within contrib/meson.

Visual Studio (Windows)

Going into build directory, you will find additional possibilities :

  • Projects for Visual Studio 2005, 2008 and 2010
    • VS2010 project is compatible with VS2012, VS2013 and VS2015
  • Automated build scripts for Visual compiler by @KrzysFR , in build/VS_scripts, which will build zstd cli and libzstd library without any need to open Visual Studio solution.

Status

Zstandard is currently deployed within Facebook. It is used daily to compress and decompress very large amounts of data in multiple formats and use cases. Zstandard is considered safe for production environments.

License

Zstandard is BSD-licensed. We also provide an additional patent grant.

Contributing

The "dev" branch is the one where all contributions will be merged before reaching "master". If you plan to propose a patch, please commit into the "dev" branch or its own feature branch. Direct commit to "master" are not permitted. For more information, please read CONTRIBUTING.

Miscellaneous

Zstd entropy stage is provided by Huff0 and FSE, from Finite State Entropy library.