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Stage C: add validation harness with real softmax reference (C1)

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biondizzle
2026-05-21 17:49:26 +00:00
parent e8485b9cf5
commit 58ca480fd1
1 changed files with 38 additions and 0 deletions
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38
tests/unit/test_fmha_v3_softmax.py
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@@ -381,3 +381,41 @@ class FmhaV3Softmax:
c_pipe.producer_tail()
tmem.relinquish_alloc_permit()
tmem.free(tmem_ptr)
def test():
"""C1 validation harness: real softmax reference."""
import math
torch.manual_seed(42)
for n in [128, 256, 384]:
m, hd = 128, HEAD_DIM
q = torch.randn(m, hd, 1, dtype=torch.bfloat16, device='cuda')
k = torch.randn(n, hd, 1, dtype=torch.bfloat16, device='cuda')
v = torch.randn(n, hd, dtype=torch.bfloat16, device='cuda')
v_kernel = v.unsqueeze(-1)
c = torch.zeros(m, hd, 1, dtype=torch.bfloat16, device='cuda')
# Real softmax reference
qf = q[:,:,0].float()
kf = k[:,:,0].float()
attn = qf @ kf.T / math.sqrt(hd)
ref = torch.softmax(attn, dim=-1) @ v.float()
mQ = ct.from_dlpack(q).mark_layout_dynamic(leading_dim=ct.get_leading_dim(q))
mK = ct.from_dlpack(k).mark_layout_dynamic(leading_dim=ct.get_leading_dim(k))
mV = ct.from_dlpack(v_kernel).mark_layout_dynamic(leading_dim=ct.get_leading_dim(v_kernel))
mC = ct.from_dlpack(c).mark_layout_dynamic(leading_dim=ct.get_leading_dim(c))
stream = cuda.CUstream(torch.cuda.current_stream().cuda_stream)
kernel = FmhaV3Softmax()
print(f'n={n}: Compiling...', flush=True)
compiled = cute.compile(kernel, mQ, mK, mV, mC, stream)
print(f'n={n}: tmem: s0={kernel.tmem_s0_offset} p0={kernel.tmem_p0_offset} o0={kernel.tmem_o0_offset} alloc={kernel.num_tmem_alloc_cols}', flush=True)
print(f'n={n}: Running...', flush=True)
compiled(mQ, mK, mV, mC, stream)
torch.cuda.synchronize()
out = c[:,:,0].float()
cos = torch.nn.functional.cosine_similarity(out.flatten().unsqueeze(0), ref.flatten().unsqueeze(0)).item()
max_err = (out - ref).abs().max().item()
print(f'FMHA softmax n={n}: cosine {cos:.6f} max_err {max_err:.6f} {"PASS" if cos >= 0.999 else "FAIL"}', flush=True)
if cos < 0.999:
print(f' out[0,:4]={out[0,:4].tolist()} ref[0,:4]={ref[0,:4].tolist()}')
if __name__ == '__main__':
test()