The unshuffle of a deflated + shuffled chunk (a panel-table HDF5 run: 8.4 MB per frame) moved one byte at
a time with the pixel size read at run time, and wrote the whole frame before it was converted. It now
assembles each 2- or 4-byte pixel from its byte planes in a loop the compiler vectorises, a 128 kB piece
at a time, and each piece is converted into the image while it is in the cache, as for an unshuffled
chunk.
Bit-identical: the FNV pixel hashes of 2000 frames on the five reader configurations are unchanged.
Reader alone on the panel-table run, 16 threads, 2000 frames: the unshuffle went from 58% of the
reader's cycles to 13%; wall 7.7-8.6 -> 5.1-7.0 s on a loaded machine.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_015CeEGgpKdfkCTJb3YNMJcu
leonarski_fandClaude Opus 5.5
33eacea54c