On P100 (GP100, sm_60) the fp16 vec kernel used for decode (batch<=8)
accumulates the online-softmax denominator and the P*V product in fp16,
flipping ~3-4% of decode top-1 tokens vs an all-fp32 reference
(llama.cpp#25593). Decode is memory-bandwidth-bound on P100, so routing
sm_60 decode to the in-tree vec_f32 kernel is free (tg128 ~identical).
Gated on cc == CC_PASCAL && Q->ne[1] <= 8 (decode only) inside the
!fp16_mma_available block, so the prefill tile_f16 path, the D=256 prefill
vec path, and fast_fp16_available() are untouched, and the
is_pascal_mla_absorbed_decode early-return (MLA) is unaffected.
Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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