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 license.s
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/Cyan4973/lz4.svg?branch=master "Continuous Integration test suite"
26[travisDevBadge]: https://travis-ci.org/Cyan4973/lz4.svg?branch=dev "Continuous Integration test suite"
27[travisLink]: https://ci.appveyor.com/project/YannCollet/lz4
28[AppveyorMasterBadge]: https://ci.appveyor.com/api/projects/status/v6kxv9si529477cq/branch/master?svg=true "Visual test suite"
29[AppveyorDevBadge]: https://ci.appveyor.com/api/projects/status/v6kxv9si529477cq/branch/dev?svg=true "Visual test suite"
30[AppveyorLink]: https://ci.appveyor.com/project/YannCollet/lz4
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 the [Open-Source Benchmark program by m^2 (v0.14.3)]
47compiled with GCC v4.8.2 on Linux Mint 64-bits v17.
48The reference system uses a Core i5-4300U @1.9GHz.
49Benchmark evaluates the compression of reference [Silesia Corpus]
50in single-thread mode.
51
52| Compressor | Ratio | Compression | Decompression |
53| ---------- | ----- | ----------- | ------------- |
54| memcpy | 1.000 | 4200 MB/s | 4200 MB/s |
55|**LZ4 fast 17 (r129)**| 1.607 |**690 MB/s** | **2220 MB/s** |
56|**LZ4 default (r129)**|**2.101**|**385 MB/s** | **1850 MB/s** |
57| LZO 2.06 | 2.108 | 350 MB/s | 510 MB/s |
58| QuickLZ 1.5.1.b6 | 2.238 | 320 MB/s | 380 MB/s |
59| Snappy 1.1.0 | 2.091 | 250 MB/s | 960 MB/s |
60| LZF v3.6 | 2.073 | 175 MB/s | 500 MB/s |
61| zlib 1.2.8 -1 | 2.730 | 59 MB/s | 250 MB/s |
62|**LZ4 HC (r129)** |**2.720**| 22 MB/s | **1830 MB/s** |
63| zlib 1.2.8 -6 | 3.099 | 18 MB/s | 270 MB/s |
64
65
66Documentation
67-------------------------
68
69The raw LZ4 block compression format is detailed within [lz4_Block_format].
70
71To compress an arbitrarily long file or data stream, multiple blocks are required.
72Organizing these blocks and providing a common header format to handle their content
73is the purpose of the Frame format, defined into [lz4_Frame_format].
74Interoperable versions of LZ4 must respect this frame format.
75
76
77Other source versions
78-------------------------
79
80Beyond the C reference source,
81many contributors have created versions of lz4 in multiple languages
82(Java, C#, Python, Perl, Ruby, etc.).
83A list of known source ports is maintained on the [LZ4 Homepage].
84
85
86[Open-Source Benchmark program by m^2 (v0.14.3)]: http://encode.ru/threads/1371-Filesystem-benchmark?p=34029&viewfull=1#post34029
87[Silesia Corpus]: http://sun.aei.polsl.pl/~sdeor/index.php?page=silesia
88[lz4_Block_format]: lz4_Block_format.md
89[lz4_Frame_format]: lz4_Frame_format.md
90[LZ4 Homepage]: http://www.lz4.org
91
