ReadRaw opened each frame with TIFFOpen(path, "r"), which memory-maps the file; on macOS the 32 MB
frame is then paged in under libtiff's copy out of it, and that copy (DumpModeDecode's memmove) was
23% of rugnux's busy CPU samples during 4nwv's image passes. With "rm" libtiff reads the file instead:
memmove 0.9% of the samples. The pixels are the same bytes either way.
Apple M6, 4nwv (the timing benchmark's moved model), alternating runs, two each:
- wall 291.1/285.9 s -> 283.4/284.5 s; system CPU 197/172 s -> 160/160 s
- pre-scan 3.9/3.8 -> 3.4/3.3 s, indexing 8.7/7.5 -> 6.8/6.9 s, metric-symmetry check 5.0/5.1 ->
2.9/3.0 s; the integration passes, bound by the GPU, within 0.6 s
p.hkl and the placed model are byte-identical. (Reading by strips straight into the frame on top of
this, TIFFReadEncodedStrip: 282.2/273.6 s, not clearly apart from "rm" alone.) On Linux the three
read paths measured the same.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_018My7tqt8a4LyKKjP3FhScT
leonarski_fandClaude Opus 5.5
90abe8670e