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Merge pull request #386 from terrelln/readme 

[pzstd] Update README
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Yann Collet 2016-09-23 23:41:20 +02:00 committed by GitHub
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@ -4,24 +4,31 @@ Parallel Zstandard is a Pigz-like tool for Zstandard.
It provides Zstandard format compatible compression and decompression that is able to utilize multiple cores.
It breaks the input up into equal sized chunks and compresses each chunk independently into a Zstandard frame.
It then concatenates the frames together to produce the final compressed output.
Optionally, with the `-p` option, PZstandard will write a 12 byte header for each frame that is a skippable frame in the Zstandard format, which tells PZstandard the size of the next compressed frame.
When `-p` is specified for compression, PZstandard can decompress the output in parallel.
Pzstandard will write a 12 byte header for each frame that is a skippable frame in the Zstandard format, which tells PZstandard the size of the next compressed frame.
PZstandard supports parallel decompression of files compressed with PZstandard.
When decompressing files compressed with Zstandard, PZstandard does IO in one thread, and decompression in another.
## Usage
PZstandard supports the same command line interface as Zstandard, but also provies the `-p` option to specify the number of threads.
Dictionary mode is not currently supported.
Basic usage
pzstd input-file -o output-file -n num-threads [ -p ] -# # Compression
pzstd -d input-file -o output-file -n num-threads # Decompression
pzstd input-file -o output-file -p num-threads -# # Compression
pzstd -d input-file -o output-file -p num-threads # Decompression
PZstandard also supports piping and fifo pipes
cat input-file | pzstd -n num-threads [ -p ] -# -c > /dev/null
cat input-file | pzstd -p num-threads -# -c > /dev/null
For more options
pzstd --help
PZstandard tries to pick a smart default number of threads if not specified (displayed in `pzstd --help`).
If this number is not suitable, during compilation you can define `PZSTD_NUM_THREADS` to the number of threads you prefer.
## Benchmarks
As a reference, PZstandard and Pigz were compared on an Intel Core i7 @ 3.1 GHz, each using 4 threads, with the [Silesia compression corpus](http://sun.aei.polsl.pl/~sdeor/index.php?page=silesia).
@ -32,8 +39,8 @@ Compression Speed vs Ratio with 4 Threads | Decompression Speed with 4 Threads
The test procedure was to run each of the following commands 2 times for each compression level, and take the minimum time.
time pzstd -# -n 4 -p -c silesia.tar > silesia.tar.zst
time pzstd -d -n 4 -c silesia.tar.zst > /dev/null
time pzstd -# -p 4 -c silesia.tar > silesia.tar.zst
time pzstd -d -p 4 -c silesia.tar.zst > /dev/null
time pigz -# -p 4 -k -c silesia.tar > silesia.tar.gz
time pigz -d -p 4 -k -c silesia.tar.gz > /dev/null