Replace the fixed-element DefaultBlockSize with a byte target divided by
elem_size to get the block element count, so the per-block working set (and
thus cache behaviour) stays constant across pixel bit depths instead of halving
from 8- to 16- to 32-bit. The target is per-algorithm, following the measured
sweet spots on sparse data: LZ4 wants a small, cache-resident block for
throughput (16 kB), ZSTD/RLE want a large block for ratio (128 kB). The gap is
widest on extreme-sparsity inputs such as the uint32 pixel_mask, where
large-block ZSTD reaches 100-1800x vs ~160x for LZ4.
The block size is read back per-dataset from the bitshuffle stream header
(block_size = header_bytes / elem_size) and the HDF5 filter params, so the
decompressor and external readers (XDS/Neggia/Durin/CrystFEL) need no change.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
leonarski_fandClaude Opus 4.8
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