Elementwise max relative error explodes on cancellation whenever a true
output element is near zero, so the mul_mat checks now gate on the
relative Frobenius norm and keep the max as information. The GEMM
fallback dequantizes to fp16 on fast-fp16 hardware and DT3 weights
(d1*t1 + d2*t2) are generally not fp16-representable, so that path is
judged against a reference computed from fp16-rounded weights (taking
the better of both references so GGML_CUDA_CUBLAS_COMPUTE_TYPE=f32 also
passes). Q4_1 (same non-fp16-exact regime) and Q4_0 (fp16-exact weights,
pure GEMM error floor) run through the identical comparison as controls.
Millaguie
b8ad6c3844