ggml-org/llama.cpp b10908

on GitHub

metal : fix idle threads in the remaining iq mul_mv kernels for ne00 < 1024 (#28692)

• metal : fix idle threads in the remaining iq mul_mv kernels for ne00 < 1024

Generalize the row split from #28086 to the six other kernels that use the
same lane-to-block mapping: iq1_s, iq1_m, iq2_xxs, iq2_xs, iq2_s and iq3_s.

Each of them assigns one 32-element chunk per thread, so when a row has
fewer than 32 chunks the rest of the simdgroup is idle. When nb32 < 32 and
nb32 divides 32, 32/nb32 threads now share each chunk and each takes a
slice of the rows, reusing the FC_mul_mv_split function constant and the
dispatch wrapper introduced for iq3_xxs.

The plain path is untouched: wide matrices keep one thread per chunk and
N_R0_ = 4. Only the split path uses N_R0__SPLIT = 8. The
K-quants have the same idle-thread issue but a different lane mapping, so
they are left for a separate change.

• metal : offset the src0 row pointer once in the iq mul_mv kernels

q2, dh, sc, qh and signs are all derived from xr, so the row slice
offset only has to be applied to xr.

• metal : fold iq mul_mv row split into offset0

Compute row0 and row1 before initializing the source pointers and apply
the row slice directly to offset0.

This keeps x and its derived pointers on the existing path while applying
the split row offset once.