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Life & fun · August 6, 2022

Thread-Parallel Decompression and Random Access to Gzip Files (Pragzip)

Hello HN, I'm very excited to have finished a gzip decoder that can speed up decompression using threads. On my Ryzen 3900X, I measured a 8x speedup over standard gzip, reaching 1.6 GB/s for a synthetic file with a consistent compression ratio of 1.3. A functional decompressor like this is kind of a first, that's why I am excited. Pragzip implements the two-staged decompression idea put forward with pugz, which unfortunately only works with gzipped text files not arbitrary files and has many more limitations. I think my main contribution over pugz might be a fast (~10 MB/s)…

Thread-Parallel Decompression and Random Access to Gzip Files (Pragzip) launched on August 6, 2022 with 15 votes, #897 of 3,307 launches that month and more than 75% of that year's launches. The site was still online in September 2026, 4 years on.

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In plain words

Pragzip is a gzip decompressor that uses multi-threading to speed up decompression of compressed files. It achieves up to 8x faster decompression than standard gzip by implementing parallel decompression across multiple threads, reaching speeds of 1.6 GB/s on compatible hardware. Unlike similar tools, Pragzip works with arbitrary gzip files rather than just text, and includes a fast deflate block finder for locating compressed data blocks. It is available as both a C++ tool and through PyPI.

written from the facts on this page · September 2026

From the sources

Gzip Decompression and Random Access for Modern Multi-Core Machines - mxmlnkn/rapidgzip

In the maker’s words, at launch

Hello HN, I'm very excited to have finished a gzip decoder that can speed up decompression using threads. On my Ryzen 3900X, I measured a 8x speedup over standard gzip, reaching 1.6 GB/s for a synthetic file with a consistent compression ratio of 1.3. A functional decompressor like this is kind of a first…

Does a similar job

all alternatives →
  • Rapidgzip – Truly Parallel Gzip Decompression with 10 GB/s2023 · github.com · ▲35

    I have posted a much earlier version of this over a year ago [0]. Since then a lot has changed. Obviously, the name has changed. This happened for the paper publication [1]. I have also optimized the speed, integrated ISA-L for special cases, limited the compression-ratio-dependent maximum memory consumption, and finally added parallelized CRC32 computation, which adds ~5% overhead no matter the number of cores used. At this point, I am leaning towards calling it production-ready although there are still many ideas for improvements. Redoing the benchmarks of the older Show HN, would look…

  • pzip- blazing fast concurrent zip archiver and extractor2023 · github.com · ▲26

    A blazing fast concurrent zip archiver and extractor. - ybirader/pzip

  • 10-40% faster LZMA decoder using x86 CMOVcc2021 · gist.github.com · ▲205

    Faster LZMA decoder for x86 CPUs (patch for XZ Utils). - faster_lzma_decoder_x86.patch

  • Mini_gzip – embeddable, minimal, in-memory Gzip API2015 · github.com · ▲21

    Embeddable minimal in-memory GZIP decompression library for embedded systems - wkoszek/mini_gzip

  • A better zip decoder2019 · github.com · ▲35

    Robust ZIP decoder with defenses against dangerous compression ratios, spec deviations, malicious archive signatures, mismatching local and central directory headers, ambiguous UTF-8 filenames, directory and symlink traversals, invalid MS-DOS dates, overlapping headers, overflow, underflow, sparsene

  • misa77 - a codec that decodes 2x faster than LZ4 (at better ratios)Jul 2026 · github.com · ▲164

    I've spent the last few months working on this codec. It has the following characteristics: - SOTA decompression throughput in its ratio class - Decent ratios (comparable to LZ4 at high effort levels) - Slow compression Most of the gains can be attributed to reducing branches and making decompression very friendly to out-of-order cores, by using a smart format. Results on the tarred Silesia corpus on Intel x86-64 follow: codec decode ratio encode misa77 -0 5219 MB/s 42.64% 54.5 MB/s misa77 -1 4274 MB/s 39.65% 51.2 MB/s lz4 2505 MB/s 47.59% 371 MB/s lz4hc -12…

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