The first device decoder walked 256-byte tiles, one thread each, straight from global memory: on a
PILATUS 6M frame (~6 MB of stream) that is ~24k threads walking alone, and the two walks took
~0.5 ms of the card per frame - with the CBF decode gone from the workers the card is what bounds
the 7qij loops (kernels 67-78 % busy). Now each thread walks a 68-byte part that its block has read
into shared memory together (68, not 64, so the threads of a warp do not read the same banks), the
scan runs over tiles of 8 parts whose maps are composed first, and the write kernel stages a block's
pixels in shared memory and writes them out coalesced.
Measured on 36 real frames of 9 CBF sets (nsys, average per frame): 0.41 ms against ~0.6 ms before.
Output unchanged: the same tests, and the same 36 frames identical to the host decoder.
Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01EizBKhTqrAYago9KJG3dA3
leonarski_fandClaude Opus 5.5
11052bc376