AuroraMiddleware/zstd
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Merge branch 'dev' into clevel_doc

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Yann Collet 2020-05-08 11:59:45 -07:00
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@ -142,23 +142,34 @@ Advanced arguments :
-q : suppress warnings; specify twice to suppress errors too
-c : force write to standard output, even if it is the console
-l : print information about zstd compressed files
--exclude-compressed: only compress files that are not previously compressed
--ultra : enable levels beyond 19, up to 22 (requires more memory)
--long : enable long distance matching (requires more memory)
--long[=#]: enable long distance matching with given window log (default: 27)
--fast[=#]: switch to very fast compression levels (default: 1)
--adapt : dynamically adapt compression level to I/O conditions
--stream-size=# : optimize compression parameters for streaming input of given number of bytes
--size-hint=# optimize compression parameters for streaming input of approximately this size
--target-compressed-block-size=# : make compressed block near targeted size
-T# : spawns # compression threads (default: 1, 0==# cores)
-B# : select size of each job (default: 0==automatic)
--rsyncable : compress using a rsync-friendly method (-B sets block size)
--no-dictID : don't write dictID into header (dictionary compression)
--[no-]check : integrity check (default: enabled)
--[no-]compress-literals : force (un)compressed literals
-r : operate recursively on directories
--output-dir-flat[=directory]: all resulting files stored into `directory`.
--format=zstd : compress files to the .zst format (default)
--format=gzip : compress files to the .gz format
--format=xz : compress files to the .xz format
--format=lzma : compress files to the .lzma format
--test : test compressed file integrity
--[no-]sparse : sparse mode (default: disabled)
-M# : Set a memory usage limit for decompression
--no-progress : do not display the progress bar
-- : All arguments after "--" are treated as files
Dictionary builder :
--train ## : create a dictionary from a training set of files
--train-cover[=k=#,d=#,steps=#,split=#,shrink[=#]] : use the cover algorithm with optional args
--train-fastcover[=k=#,d=#,f=#,steps=#,split=#,shrink[=#],accel=#] : use the fastcover algorithm with optional args
--train-fastcover[=k=#,d=#,f=#,steps=#,split=#,accel=#,shrink[=#]] : use the fast cover algorithm with optional args
--train-legacy[=s=#] : use the legacy algorithm with selectivity (default: 9)
-o file : `file` is dictionary name (default: dictionary)
--maxdict=# : limit dictionary to specified size (default: 112640)
@ -208,12 +219,12 @@ Compression Speed vs Ratio | Decompression Speed
| Method | Compression ratio | Compression speed | Decompression speed |
|:-------|------------------:|-------------------------:|---------------------------:|
| `zstd -1` | `5.065` | `284.8 MB/s` | `759.3 MB/s` |
| `zstd -1` | `5.065` | `284.8 MB/s` | `759.3 MB/s` |
| `zstd -5` | `5.826` | `124.9 MB/s` | `674.0 MB/s` |
| `zstd -10` | `6.504` | `29.5 MB/s` | `771.3 MB/s` |
| `zstd -1 --long` | `17.426` | `220.6 MB/s` | `1638.4 MB/s` |
| `zstd -5 --long` | `19.661` | `165.5 MB/s` | `1530.6 MB/s`|
| `zstd -10 --long`| `21.949` | `75.6 MB/s` | `1632.6 MB/s`|
| `zstd -5 --long` | `19.661` | `165.5 MB/s` | `1530.6 MB/s` |
| `zstd -10 --long`| `21.949` | `75.6 MB/s` | `1632.6 MB/s` |
On this file, the compression ratio improves significantly with minimal impact
on compression speed, and the decompression speed doubles.