README.md
1LZ4 - Extremely fast compression
2================================
3
4LZ4 is lossless compression algorithm,
5providing compression speed at 400 MB/s per core,
6scalable with multi-cores CPU.
7It features an extremely fast decoder,
8with speed in multiple GB/s per core,
9typically reaching RAM speed limits on multi-core systems.
10
11Speed can be tuned dynamically, selecting an "acceleration" factor
12which trades compression ratio for more speed up.
13On the other end, a high compression derivative, LZ4_HC, is also provided,
14trading CPU time for improved compression ratio.
15All versions feature the same decompression speed.
16
17LZ4 library is provided as open-source software using BSD 2-Clause license.
18
19
20|Branch |Status |
21|------------|---------|
22|master | [![Build Status][travisMasterBadge]][travisLink] [![Build status][AppveyorMasterBadge]][AppveyorLink] [![coverity][coverBadge]][coverlink] |
23|dev | [![Build Status][travisDevBadge]][travisLink] [![Build status][AppveyorDevBadge]][AppveyorLink] |
24
25[travisMasterBadge]: https://travis-ci.org/lz4/lz4.svg?branch=master "Continuous Integration test suite"
26[travisDevBadge]: https://travis-ci.org/lz4/lz4.svg?branch=dev "Continuous Integration test suite"
27[travisLink]: https://travis-ci.org/lz4/lz4
28[AppveyorMasterBadge]: https://ci.appveyor.com/api/projects/status/jc2yhgwyc7qqtsko/branch/master?svg=true "Windows test suite"
29[AppveyorDevBadge]: https://ci.appveyor.com/api/projects/status/jc2yhgwyc7qqtsko/branch/dev?svg=true "Windows test suite"
30[AppveyorLink]: https://ci.appveyor.com/project/YannCollet/lz4-1lndh
31[coverBadge]: https://scan.coverity.com/projects/4735/badge.svg "Static code analysis of Master branch"
32[coverlink]: https://scan.coverity.com/projects/4735
33
34> **Branch Policy:**
35
36> - The "master" branch is considered stable, at all times.
37> - The "dev" branch is the one where all contributions must be merged
38 before being promoted to master.
39> + If you plan to propose a patch, please commit into the "dev" branch,
40 or its own feature branch.
41 Direct commit to "master" are not permitted.
42
43Benchmarks
44-------------------------
45
46The benchmark uses [lzbench], from @inikep
47compiled with GCC v6.2.0 on Linux 64-bits.
48The reference system uses a Core i7-3930K CPU @ 4.5GHz.
49Benchmark evaluates the compression of reference [Silesia Corpus]
50in single-thread mode.
51
52[lzbench]: https://github.com/inikep/lzbench
53[Silesia Corpus]: http://sun.aei.polsl.pl/~sdeor/index.php?page=silesia
54
55| Compressor | Ratio | Compression | Decompression |
56| ---------- | ----- | ----------- | ------------- |
57| memcpy | 1.000 | 7300 MB/s | 7300 MB/s |
58|**LZ4 fast 8 (v1.7.3)**| 1.799 |**911 MB/s** | **3360 MB/s** |
59|**LZ4 default (v1.7.3)**|**2.101**|**625 MB/s** | **3220 MB/s** |
60| LZO 2.09 | 2.108 | 620 MB/s | 845 MB/s |
61| QuickLZ 1.5.0 | 2.238 | 510 MB/s | 600 MB/s |
62| Snappy 1.1.3 | 2.091 | 450 MB/s | 1550 MB/s |
63| LZF v3.6 | 2.073 | 365 MB/s | 820 MB/s |
64| [Zstandard] 1.1.1 -1 | 2.876 | 330 MB/s | 930 MB/s |
65| [Zstandard] 1.1.1 -3 | 3.164 | 200 MB/s | 810 MB/s |
66| [zlib] deflate 1.2.8 -1| 2.730 | 100 MB/s | 370 MB/s |
67|**LZ4 HC -9 (v1.7.3)** |**2.720**| 34 MB/s | **3240 MB/s** |
68| [zlib] deflate 1.2.8 -6| 3.099 | 33 MB/s | 390 MB/s |
69
70[zlib]: http://www.zlib.net/
71[Zstandard]: http://www.zstd.net/
72
73LZ4 is also compatible and well optimized for x32 mode, for which it provides +10% speed performance.
74
75
76Documentation
77-------------------------
78
79The raw LZ4 block compression format is detailed within [lz4_Block_format].
80
81To compress an arbitrarily long file or data stream, multiple blocks are required.
82Organizing these blocks and providing a common header format to handle their content
83is the purpose of the Frame format, defined into [lz4_Frame_format].
84Interoperable versions of LZ4 must respect this frame format.
85
86[lz4_Block_format]: doc/lz4_Block_format.md
87[lz4_Frame_format]: doc/lz4_Frame_format.md
88
89
90Other source versions
91-------------------------
92
93Beyond the C reference source,
94many contributors have created versions of lz4 in multiple languages
95(Java, C#, Python, Perl, Ruby, etc.).
96A list of known source ports is maintained on the [LZ4 Homepage].
97
98[LZ4 Homepage]: http://www.lz4.org
99