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Fix FP4 init range for nvfp4_group_gemm #96

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Fix FP4 init range for nvfp4_group_gemm #96

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21 changes: 13 additions & 8 deletions problems/nvidia/nvfp4_group_gemm/reference.py
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Original file line number Diff line number Diff line change
Expand Up @@ -123,6 +123,17 @@ def create_reordered_scale_factor_tensor(l, mn, k, ref_f8_tensor):
return reordered_f8_tensor


def _create_fp4_tensors(l, mn, k):
# generate uint8 tensor, then convert to float4e2m1fn_x2 data type
# generate all bit patterns
ref_i8 = torch.randint(255, size=(l, mn, k // 2), dtype=torch.uint8, device="cuda")

# for each nibble, only keep the sign bit and 2 LSBs
# the possible values are [-1.5, -1, -0.5, 0, +0.5, +1, +1.5]
ref_i8 = ref_i8 & 0b1011_1011
return ref_i8.permute(1, 2, 0).view(torch.float4_e2m1fn_x2)


def generate_input(
m: tuple,
n: tuple,
Expand Down Expand Up @@ -165,14 +176,8 @@ def generate_input(
mi = m[group_idx]
ni = n[group_idx]
ki = k[group_idx]
a_ref = torch.randint(
-1, 2, (l, mi, ki // 2), dtype=torch.int8, device="cuda"
).permute(1, 2, 0)
b_ref = torch.randint(
-1, 2, (l, ni, ki // 2), dtype=torch.int8, device="cuda"
).permute(1, 2, 0)
a_ref = a_ref.view(torch.float4_e2m1fn_x2)
b_ref = b_ref.view(torch.float4_e2m1fn_x2)
a_ref = _create_fp4_tensors(l, mi, ki)
b_ref = _create_fp4_tensors(l, ni, ki)

c_ref = torch.randn((l, mi, ni), dtype=torch.float16, device="cuda").permute(
1, 2, 0
Expand Down