Function fa512_wide_warps 

pub fn fa512_wide_warps() -> usize

4-warp sp16 experiment arm (MEMRA_FA512_W4=1, requires the f16pv door): GEMM0 split-K 4-way + GEMM1 4x128 O-dims. Own partial-sum order — oracle-band gated. Returns warp count (2 = base sp16). 8-warp arm measured NEGATIVE 2026-07-23 (jsonl) and removed.