| # Parallel Zstandard (PZstandard) |
| |
| 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. |
| 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 provides the `-p` option to specify the number of threads. |
| Dictionary mode is not currently supported. |
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| Basic usage |
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| pzstd input-file -o output-file -p num-threads -# # Compression |
| pzstd -d input-file -o output-file -p num-threads # Decompression |
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| PZstandard also supports piping and fifo pipes |
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| cat input-file | pzstd -p num-threads -# -c > /dev/null |
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| For more options |
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| pzstd --help |
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| 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 |
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| 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). |
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| Compression Speed vs Ratio with 4 Threads | Decompression Speed with 4 Threads |
| ------------------------------------------|----------------------------------- |
|  |  |
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| The test procedure was to run each of the following commands 2 times for each compression level, and take the minimum time. |
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| time pzstd -# -p 4 -c silesia.tar > silesia.tar.zst |
| time pzstd -d -p 4 -c silesia.tar.zst > /dev/null |
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| time pigz -# -p 4 -k -c silesia.tar > silesia.tar.gz |
| time pigz -d -p 4 -k -c silesia.tar.gz > /dev/null |
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| PZstandard was tested using compression levels 1-19, and Pigz was tested using compression levels 1-9. |
| Pigz cannot do parallel decompression, it simply does each of reading, decompression, and writing on separate threads. |
| |
| ## Tests |
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| Tests require that you have [gtest](https://github.com/google/googletest) installed. |
| Set `GTEST_INC` and `GTEST_LIB` in `Makefile` to specify the location of the gtest headers and libraries. |
| Alternatively, run `make googletest`, which will clone googletest and build it. |
| Run `make tests && make check` to run tests. |
