1 # Parallel Zstandard (PZstandard)
3 Parallel Zstandard is a Pigz-like tool for Zstandard.
4 It provides Zstandard format compatible compression and decompression that is able to utilize multiple cores.
5 It breaks the input up into equal sized chunks and compresses each chunk independently into a Zstandard frame.
6 It then concatenates the frames together to produce the final compressed output.
7 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.
8 PZstandard supports parallel decompression of files compressed with PZstandard.
9 When decompressing files compressed with Zstandard, PZstandard does IO in one thread, and decompression in another.
13 PZstandard supports the same command line interface as Zstandard, but also provides the `-p` option to specify the number of threads.
14 Dictionary mode is not currently supported.
18 pzstd input-file -o output-file -p num-threads -# # Compression
19 pzstd -d input-file -o output-file -p num-threads # Decompression
21 PZstandard also supports piping and fifo pipes
23 cat input-file | pzstd -p num-threads -# -c > /dev/null
29 PZstandard tries to pick a smart default number of threads if not specified (displayed in `pzstd --help`).
30 If this number is not suitable, during compilation you can define `PZSTD_NUM_THREADS` to the number of threads you prefer.
34 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](https://sun.aei.polsl.pl//~sdeor/index.php?page=silesia).
36 Compression Speed vs Ratio with 4 Threads | Decompression Speed with 4 Threads
37 ------------------------------------------|-----------------------------------
38 ![Compression Speed vs Ratio](images/Cspeed.png "Compression Speed vs Ratio") | ![Decompression Speed](images/Dspeed.png "Decompression Speed")
40 The test procedure was to run each of the following commands 2 times for each compression level, and take the minimum time.
42 time pzstd -# -p 4 -c silesia.tar > silesia.tar.zst
43 time pzstd -d -p 4 -c silesia.tar.zst > /dev/null
45 time pigz -# -p 4 -k -c silesia.tar > silesia.tar.gz
46 time pigz -d -p 4 -k -c silesia.tar.gz > /dev/null
48 PZstandard was tested using compression levels 1-19, and Pigz was tested using compression levels 1-9.
49 Pigz cannot do parallel decompression, it simply does each of reading, decompression, and writing on separate threads.
53 Tests require that you have [gtest](https://github.com/google/googletest) installed.
54 Set `GTEST_INC` and `GTEST_LIB` in `Makefile` to specify the location of the gtest headers and libraries.
55 Alternatively, run `make googletest`, which will clone googletest and build it.
56 Run `make tests && make check` to run tests.