CHANGELOG.md

Version 0.13.3 built on 2024-04-27

Fixes

• Reading after seeking could fail in some cases because of a bug with the window compression.
• RapidgzipFile verbose parameter did not have any effect.
• Add newline after --count or --count-lines result.

Version 0.13.2 built on 2024-04-22

Fixes

• Disable vmsplice usage on -c/--stdout because it can result in wrong output if rapidgzip quits before all of the splice output has been read from stdin of the piped to process.

Version 0.13.1 built on 2024-03-25

Fixes

• The verbose argument was accidentally used to initialize the chunk size with 0 or 1, resulting in the minimum chunk size of 8 KiB being used, which can result in decompression errors for false positives and which slows down decompression to a crawl.

Version 0.13.0 built on 2024-02-04

Added

• Use ISA-L CRC32 computation, which uses PCLMULQDQ if available
• Improve profiling output on --verbose.
• Add support for bzip2 decompression via the ParallelGzipReader architecture. This is one small step to a unified parallelized and seekable decoder for multiple formats.
• Expose chunk size and I/O read method to Python interface.

Performance

• Compress windows for chunks with large compression ratios in memory to reduce the memory footprint. This reduces the memory usage for working with wikidata-20220103-all.json.gz from 20 GB down to 12 GB and can have even larger effects for larger files. The compression ratio threshold and the compression being done in parallel keeps the overhead for this memory optimization to a minimum.
• Avoid temporary allocations for internal SharedFileReader::getLock calls.
• Automatically adjust chunk size for "small" files and large parallelizations.
• Use faster short-/long-LUT Huffman decoder if compiled without ISA-L.

API

• Change template parameter ENABLE_STATISTICS into a member.
• Move ChunkData statistics into a subclass.

Fixes

• Return only an appropriate exit code instead of showing a Python stacktrace in case of a broken pipe signal.
• Avoid segfault when exporting the index for an empty, invalid gzip file.
• Use isatty instead of poll with 100ms timeout to determine whether rapidgzip is piped to.
• Fix build error on macOS when no wheel are available.
• Many smaller adjustmenst to the profiling output with --verbose.
• Do not terminate with an error when trying to unlock the GIL during Python finalization

Version 0.12.1 built on 2024-01-08

Fixes

• Fix segmentation fault from rpmalloc because rpmalloc_thread_initialize was not called because the static thread_local global variable was not initialized at all because it was never used.

Version 0.12.0 built on 2024-01-07

Added

• Add support for zlib and raw deflate files.
• Add --oss-attributions-yaml command line option to generate a Conda-compatible THIRDPARTY.yml.

API

• Add rapidgzip::VERSION and other preprocessor version macros.
• Add setDeflateStreamCRC32s and addDeflateStreamCRC32 for providing CRC32s for raw deflate streams.
• Add RapidgzipFile.file_type getter and determineFileType to get the determined file type. Currently, it is one of the values GZIP, BGZF, ZLIB, DEFLATE, None.

Version 0.11.2 built on 2024-01-06

Fixes

• Fix segfault with rpmalloc when creating a ParallelGzipReader object on one thread and using it into another thread created manually in Python.

Version 0.11.1 built on 2023-12-22

Fixes

• Fix possible GIL deadlock when calling many RapidgzipFile methods in quick succession.

Version 0.11.0 built on 2023-12-19

Added

• Make parallel decompression work from stdin and other non-seekable inputs.
• The setup.py file now comes with fine-granular dependency control via the environment variables: RAPIDGZIP_BUILD_CXXOPT, RAPIDGZIP_BUILD_ISAL, RAPIDGZIP_BUILD_RPMALLOC, RAPIDGZIP_BUILD_ZLIB, which can be set to enable, disable, or system. Cxxopts and zlib may not be disabled.
• Include indexed_bzip2 classes and CLI method with the rapidgzip Python module. This only adds ~15% space overhead to the precompiled binaries. This is a step towards one Python module offering seekable access to many different file formats.
• Add import/export timings with --verbose.
• Enable checksum verification by default. This adds ~5 % overhead.
• Show a message about mismatching CRC32 during --analyze but try to read further.
• Track symbol usage in windows and show information with --analyze.
• Reorganize output of --help.
• Add --io-read-method=... option, which can be set to pread, sequential, or locked-read. --io-read-method=sequential is advisable when decompressing from files on slow I/O devices such as HDDs.
• Add RapidgzipFile.peek method.

Performance

• Clear seek points / windows when they are not needed, e.g., for one-pass sequential decompression without --export-index. This reduces the memory usage for decompressing wikidata-20220103-all.json.gz from 20 GB down to 10 GB and can have even larger effects for larger files.
• Avoid doubling memory usage during index import and export by streaming the data directly to the output file without an internal copy.

Fixes

• Show better error message when quitting via SIGINT during a long-running read loop over a RapidgzipFile object working on a Python file object without using Python context managers / the with-statement. This leads to the decompression threads being left running and trying to acquire a non-existing GIL while Python interpreter finalization has already started.
• Fix compile error when compiling with Conda because it defines __linux__ while not having F_GETPIPE_SZ.
• Improve error messages on EOF, for ISA-L and Zlib wrappers, and when file seeking fails.

API

• Change size_t FileReader::size() to std::optional<size_t> FileReader::size()

Version 0.10.5 built on 2024-02-22

Fixes

• Fix segfault with rpmalloc when creating a ParallelGzipReader object on one thread and using it into another thread created manually in Python.
• Fix possible GIL deadlock when calling many RapidgzipFile methods in quick succession.
• Fix many issues with the GIL acquirement code logic.
• Avoid segfault when exporting the index for an empty, invalid gzip file.
• Use isatty instead of poll with 100ms timeout to determine whether rapidgzip is piped to.
• Fix build error on macOS when no wheel are available.

Version 0.10.4 built on 2023-11-25

Fixes

• Do not warn about the output file when it is not used.
• The encoded end offset check on the chunk fired erroneously when decoding with an imported index.
• Do not needlessly decompress for these command line combinations:
  • rapidgzip --import-index <index> --export-index <index>, which currently can be used to check and copy an index and in the future can be used to convert index formats.
  • rapidgzip --import-index <index> --count, which can be used to quickly print the decompressed file size.
• The combination --export-index -d did not work.
• Size formatting with units did drop any parts larger than 1 TiB.
• Avoid error for --count --no-verify -P 1.
• Avoid error for --count --no-verify for some files with large compression ratios.
• Only print the decompression duration and bandwidth with -v.
• Fix some typos.
• Fix "Python memory allocator called without holding the GIL" consistency check with PYTHONDEVMODE=1 or python3 -X dev. No actual race condition has been observed. All Python callbacks were always serialized.
• Add tests for many command line parameter combinations.

Version 0.10.3 built on 2023-09-12

Fixes

• Do not build with ISA-L on aarch64 for now because it fails.

Version 0.10.2 built on 2023-09-10

Fixes

• fileno did not work because of an inverted smart pointer check.

Version 0.10.1 built on 2023-09-04

Fixes

• Avoid crash on some MSVC versions during building the project. This happened only for the Conda builds, not the Windows wheel builds.

Version 0.10.0 built on 2023-09-03

Performance

• Several miniscule performance improvements in BitReader and HuffmanCodingISAL: +10 %

Fixes

• Make export_index work with non-seekable output Python file objects.
• Add the -mmacosx-version-min=10.14 compiler option on macOS to avoid build problems.
• Avoid possible race condition when checking for markers in chunk data.

Version 0.9.0 built on 2023-08-30

Added

• Support BGZI with --import-index. These can be created with bgzip --reindex.
• Check against a wrong index being loaded.
• Improve error messages when zlib or ISA-l wrappers are used.
• New output with --analyze:
  • Show information about extra bytes written by pgzf, MiGz, QATzip, pgzip/mgzip, bgzip, dictzip.
  • Print stream size statistics.
  • Print out the position after the block header, i.e., the begin of the Huffman data.
• New profiling output with --verbose:
  • Decompression durations split by ISA-l, zlib, rapidgzip internal
  • The number of block offsets found with a block finder, from which decoding failed inside a chunk

Performance

• Avoid allocations by replacing the markers in-place by reinterpreting the buffer: Silesia +11 %, FASTQ +36 %.
• Allocate fixed 128 KiB chunks instead of one allocation per deflate block: FASTQ +3 %.
• Use ISA-L, if available, with -P 1: +110%.
• Use ISA-L when a window has become resolve inside a chunk: Silesia +12%, Random Base64 +70%.
• Use ISA-l Huffman decoder for literal/length alphabet in internal decoder: +20-40%.

Fixes

• Only show informational message about internal chunk fetcher with --verbose.
• Smaller fixes in the inflate wrappers.
• Check against zero-length end-of-block symbol.
• Reintroduce the error detection for distance code counts equal to 31 or 32, which was removed in 0.5.0.

API

• Add stopping points to inflate wrappers.
• SharedFileReader: Decouple statistics recording from printing.
• Add VectorView constructor taking a start and end pointer.
• Remove unused deflate::Block::window method.
• Make SHOW_PROFILE a simple bool member instead of template parameter.
• Make DecodedData::data private and a vector of views to actual buffers.
• Add BufferViewFileReader(void*, size_t) overload
• Remove unused argument to ParallelGzipReader::maxDecompressedChunkSize() getter.

Version 0.8.1 built on 2023-08-04

Fixes

• The CRC32 checksum was not correctly read from the footer when ISA-l was used.
• Limit the minimum chunk size to 8 KiB, especially forbid a chunk size of 0, which lead to an infinite loop.

Version 0.8.0 built on 2023-08-04

Performance

• Use ISA-l instead of zlib when decompressing with an existing index: 5.5 GB/s -> 8.0 GB/s. Probably even better speedups depending on the file and number of available cores. In single-threaded benchmarks, ISA-l often outperformed zlib by factor 2 to 3.
• Use ISA-l for BGZF files (.bgz) even when an index is not available: 3.5 GB/s -> 8.0 GB/s. This obviates the need for indexes for BGZF files.

Version 0.7.1 built on 2023-08-01

Fixes

• Add exception for some BGZF files when decompressing when with an imported index. Bug got introduced in 0.5.0 when adding additional seek points for one heuristically chosen large chunk.

Performance

• Avoid overallocations when decompressing BGZF files with an imported index: 3.5 GB/s -> 5.8 GB/s.

Version 0.7.0 built on 2023-06-04

• Rename pragzip to rapidgzip. See the About section in the Readme for some background.

Version 0.6.0 built on 2023-05-30

Added

• Add --verify option to turn on CRC32 computation. The overhead is ~6% thanks to parallelizing the CRC32 computation and thanks to using the the slice-by-n implementation where n is a template argument and n=16 was found to be optimal. It achieves 4.5 GB/s on a single core and parallelizes almost trivially thanks to crc32_combine.
• Add Open-Source Software attributions listing option with: --oss-attributions.
• Profile the time spent allocating and copying when using the --verbose argument.
• Show SharedFileReader statistics with --verbose.
• pragzip --analyze:
  • Print code length histograms for the whole file for all three alphabets.
  • Print gzip footer information.

Performance

• Reduce the maximum memory usage by 50x by limiting the chunk size. This means that for compression ratios larger than 20x, the decompression gets effectively serialized. However, in cases of very large compression ratios, the optimizations below will reach much faster speeds to offset this slowdown. This puts the estimate for the maximum memory usage during decompression using pragzip at:
  • chunk size * ( prefetch count + resident cache size ) * maximum compression ratio * parallelization
  • = 4 MiB * ( 2 * parallelization + 1 ) * 20 * parallelization
  • ≈ 160 MiB * parallelization
• Inflate:
  • Use memset and memcpy to resolve backreferences. This speeds up performance for files consisting only of zeros from 360 MB/s -> 1940 MB/s. The performance on the Silesia dataset is: 201 MB/s -> 250 MB/s.
  • Check for rare output buffer wrap-around once per back-reference. Performance with Silesia: 182 -> 201 MB/s.
• Block fetcher:
  • Avoid waiting for non-existing blocks.
  • Avoid prefetching the same failed offsets multiple times.
• Stop looking for blocks after 512 KiB to avoid slower than single-core performance for BGZF-like files: 100 -> 230 MB/s.
• Use rpmalloc to increase multi-threaded malloc performance: 2.5 GB/s -> 3.1 GBs. The performance benefits are less noticable for files larger than ~10 GB.
• Add verbose option to the Python interfaces open and PragzipFile.
• Spawn threads only when needed instead of all at once at startup.
• Reduce memory usage by not storing the decompressed result when using only --count.

Fixes

• Quit on SIGINT (Ctrl+C) while using the CLI via Python with the --analyze argument.
• Do not throw an EOF exception for an empty gzip-compressed file when decompression in parallel.
• Show default chunk size in pragzip CLI help.
• Do not open an output file when only --export-index but -d has not been specified.
• Improve error message for non-existing or empty input file.
• Fix tellCompressed to return the file size instead of 0 at the end of the file.
• Profiling output displayed with --verbose:
  • Also count decode time of blocks that do not need marker replacement.
  • Seek back/forward statistics were wrong when using pread.
  • Fix cache misses metric.
• Avoid std::regex initialization during dlopen.

API

• Remove pragzip/blockfinder/Combined.hpp and pragzip/blockfinder/Skipping.hpp
• Move ZlibDeflateWrapper into pragzip/zlib.hpp.
• Move DecodedDataView into pragzip/DecodedDataView.hpp.
• Return smart pointer on FileReader::clone.
• Add BlockFinderInterface, which all block finders derive from and implement.
• Add FileReaderStream, which is a thin wrapper around a given FileReader, including ParallelGzipReader, and adapts the std::istream interface so that it can be used interchangibly to std::ifstream and others in C++ code.

Version 0.5.0 built on 2023-01-29

Added

• Add --count-lines option to count lines faster by avoiding to pipe to wc -l.
• Add a performance profile and index seek point statistics when using the --verbose option.
• By default, start only as many threads as there are cores pragzip has affinity for.
• The seek points are now chosen such that the decompressed size instead of the compressed size approximates the chunk size. This behavior is similar to indexed_gzip and improves decompression speed and memory usage when loading such an optimized index.
• Add --export-index and --import-index options. Using an existing index is not only faster but also reduces the maximum memory consumption significantly.

Performance

• Uncompressed block finder
  • Avoid full seeks: 90 -> 380 MB/s.
  • Keep track of buffer outside of BitReader: 380 -> 430 MB/s.
• Marker replacement:
  • Reduce branches: 800 -> 1400 MB/s (8-bit output bandwidth).
  • Parallelize marker replacement to scale parallel decompression for files with lots of LZSS backward pointers like the Silesia corpus to 16 cores and more.
• File writing:
  • Use vectorized I/O output to avoid many small calls of 30 KiB: 2.3 GB/s -> 2.4 GB/s.
  • Reuse an existing output file to avoid costly fallocate: 2.4 GB/s -> 3.0 GB/s.

Fixes

• Quit when SIGINT has been sent while using the CLI via Python.
• Also print errno as string when I/O write fails.
• Fix erroneous error detection for distance code counts equal to 31 or 32. I was not able to find or reproduce a gzip file with those code counts but in principle they are possible.
• Avoid crash when using --analyze to print alphabet information for uncompressed blocks.
• Ensure sure that Huffman coding structures can be reused after initializeFromLengths.
• Improve error message for truncated gzip files.
• Remove special case handling for /dev/null.
• Fix multi-stream gzip file support by reading over gzip footers when decoding with zlib.

API

• Renamings:
  • GzipBlockFetcher -> GzipChunkFetcher
  • ThreadPool::submitTask -> ThreadPool::submit
  • FetchNext -> FetchNextFixed
  • FetchNextSmart -> FetchNextAdaptive
  • FetchNextMulti -> FetchMultiStream
• Call write callback with full results instead of once per contiguous memory chunk.
• Make the SharedFileReader constructor with unclear ownership semantic private.
• Add thread pool priorities.

Version 0.4.0 built on 2022-11-10

API

• Move ParallelGzipReader into pragzip namespace.

Added

• Show compression type and ratio statistics with pragzip --analyze.

Fixes

• An empty precode alphabet was not detected as a faulty block and threw instead.
• There was an erroneous exception for a block with a single symbol with code length 1.
• Bit-reversing was bugged in rare if not impossible instance.
• When piping the output, splicing might have resulted in invalid data in some circumstances.

Performance

• Decoding of uncompressed blocks:
  • Unaligned uncompressed blocks are now correctly found.
  • Speed up deflate loop by unrolling and avoid calls to std::fread and BitReader::read.
  • Fall back to memcpy for uncompressed blocks.
  • Use pread to reduce locks inside SharedFileReader for better uncompressed bandwidth: 2.7 -> 3.6 GB/s.
• Block finder:
  • Make checkPrecode constexpr.
  • Keep 74 bits of buffer to avoid seek backs.
  • Use different Huffman Coding implementation for precode.
  • Replace uninteresting zero-count with non-zero-count in histogram.
  • Only do Huffman Coding checks and skip preparations for actual decoding.
  • Compile-time calculate all possible 1526 precode Huffman Codings.
• Huffman decoding:
  • Only create Huffman LUT up to max code length in block: 140 -> 195 MB/s.
  • Decrease double-cached Huffman LUT cached bits: 165 -> 255 MB/s.
• Reduce memory usage:
  • Remove previous blocks from the cache for the purely-sequential use case.
  • Avoid std::vector overallocations and reallocations.
• Prefetching did not work when calling ParallelGzipReader::read multiple times with small values.
• Uncompressed blocks directly before untilOffset were not found.
• The very last block was never prefetched.
• Avoid cache eviction when key already exists and value can be replaced.
• Prefetch more blocks while waiting for non-completed block.
• Actively avoiding cache-spilling was disfunctional.

Version 0.3.0 built on 2022-08-24

Added

• --count-lines option to integrate the functionality of wc -l and saving time piping the output.
• --chunk-size option to adjust the work chunk size. The preset of 2 MiB should be good enough in most cases but it still might be desirable to reduce the memory usage by reducing the chunk size at the cost of speed.
• Default argument (SEEK_SET) for "whence" in the "seek" method.

Performance

• Alternatingly look for uncompressed blocks and deflate blocks in small chunks. This fixes a performance degradation from 1.4 GB/s down to 1.0 GB/s introduced in 0.2.2.
• Speed up the compressed block finder by more than 3x.
• Double the work chunk size to increase speed by ~30%.
• Increase speed when piping by ~10% by using vmsplice on Linux.

Version 0.2.2 built on 2022-08-09

Fixes

• Specified output (-o) was ignored by pragzip.
• An exception was thrown for very large runs of incompressible data because only 2147479552 B could be written.

Performance

• Improve performance for gzips with uncompressed deflate blocks.

Version 0.2.1 built on 2022-08-07

Fixes

• An exception was thrown when decoding gzips with many consecutive uncompressed blocks in parallel.

Version 0.2.0 built on 2022-08-05

Added

• Add support for parallel decompression of arbitrary gzip files even without a preexisting gzip index file.
• Add the command line tool pragzip to be used as a replacement for decoding gzip files.
• Add import_index method that actually works to Python interface.
• Add export_index method to Python interface.

Fixes

• Fix segmentation fault when the IndexedBzip2File constructor fails.
• Fix exception being thrown when gzip index is empty, which might happen for gzip smaller than approximately 64 KiB.
• Fix race condition for fixed Huffmann coding deflate blocks.

Performance

• Speed up parallel decoding by reducing prefetcher cache pollution.
• Speed up parallel decompression speed by 2x when the gzip index is known by using zlib in that case.

Version 0.1.0 built on 2022-07-03

• First prototype to be used with ratarmount for significant speedups over indexed_gzip.