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RELEASE_NOTES.rst

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Release notes for C-Blosc2 2.0.0a4 (fourth alpha)

Author: Francesc Alted
Contact: [email protected]
URL:http://www.blosc.org

Changes from 2.0.0a3 to 2.0.0a4

  • New filter pipeline designed to work inside a chunk. The pipeline has a current capacity of 5 slots, and is designed to apply different filters sequentially over the same chunk. For this, a new extended header for the chunk has been put in place (see README_HEADER.rst).
  • New delta filter meant to work inside a chunk. Previously delta was working inside a super-chunk, but the new implementation is both faster and simpler and gets better compression ratios (at least for the tested datasets).
  • New re-parametrization of BloscLZ for improved compression ratio and also more speed (at least on modern Intel/AMD CPUs). Version for internal BloscLZ codec bumped to 1.0.6.
  • Internal zstd sources bumbed to 1.3.0.

Changes from 2.0.0a2 to 2.0.0a3

  • New blosc2_create_context() and blosc2_free_context() for creating contexts so that Blosc can be used from threaded applications without the global lock. For now contexts can be only used from blosc2_compress_ctx() and blosc2_decompress_ctx() (see below).
  • The blosc_compress_ctx() and blosc_decompress_ctx() have been replaced by blosc2_compress_ctx() and blosc2_decompress_ctx() that do accept actual contexts.
  • Added support for new Zstd codec (https://github.com/Cyan4973/zstd). This is a new compressor by Yann Collet, the author of LZ4 and LZ4HC. For details on Zstd, see this nice intro: http://fastcompression.blogspot.com.es/2015/01/zstd-stronger-compression-algorithm.html.
  • The blosc2_append_chunk() has been removed. This is this because an existing chunk may not fulfill the sequence of filters in super header. It is best that the user will use blosc2_append_buffer() and compress it internally.
  • The split of blocks only happens for BLOSCLZ and SNAPPY codecs. All the rest are not split at all. This allows for faster operation for the rest of codecs (most specially zstd).
  • The internal zlib 1.2.8 sources have been replaced by the miniz library, which is meant to be fully compatible with Zlib, but much smaller and besides tends to be a bit faster. Also, miniz is preferred to an external Zlib.
  • The internal snappy sources have been removed. If snappy library is found, the support for it is still there.
  • Internal LZ4 sources upgraded to 1.7.1.

Changes from 2.0.0a1 to 2.0.0a2

  • The delta filter runs inside of the compression pipeline.
  • Many fixes for the delta filter in super-chunks.
  • Added tests for delta filter in combination with super-chunks.