The device scaling's peak, measured with nsys on four large sets (33-123 M observations, 4-16 M
distinct hkl), is 81 bytes an observation plus 291 bytes a distinct hkl to within 5%. Once the
ingest has counted both, an engine whose estimate is over 80% of the card's total memory scales on
the CPU instead, with one warning line saying why; a resident ingest is made again on the host,
which the CPU path needs. Decided once, before anything is scaled, on the card's total memory: the
answer depends on the card, not on the moment.
On a simulated 8 GB card (total clamped to 8.2e9, 7.75 GB free) a 33 M-observation, 15 M-hkl set
whose final merge alone needs ~7.5 GB on the GPU ran out of memory there; it now completes, and its
merged MTZ matches the 16 GB GPU run to float rounding (max relative difference 9e-7 on any
intensity column, same reflections, cell, space group and resolution cut). The largest estimate on
the battery is 12.45 GB, under 80% of a 16 GB card, so nothing changes there.
The all-observations arm is copied from the engine's card arrays only when that engine is on the
GPU.
Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
leonarski_fandClaude Opus 5.5
beba8f0301