pub fn sphere_kernel_decision(n: usize, m: usize, lmax: usize) -> GpuDecisionExpand description
Decide whether the GPU sphere kernel matrix path is eligible for
(n, m, lmax). Heuristic per the math spec:
n * m >= 1_000_000lmax <= 200- device memory budget admits at least one
(ld × m)design atld = ((n + 31) / 32) * 32.