[ROCm] Fix mx fp8 and fp4 code after scaling refactor changes. (#163127)

PR #151360 added mx fp8 and fp4 support on ROCm.
1. However, on recent upstream, scaling function in Blas.cpp along with test_matmul_cuda changes triggered failures.
This patch corrects is_blockwise_1x32_scaling function code.

2. Fixes the m, n, k dimensions for ROCm mx case.

3.  Modify FP4E2M1FN_LARGEST_POW2 (largest power of 2 representable in `torch.float4_e2m1fn_x2`) to 2.
This resulted in higher SQNR value for mx fp4 test.

Testing result on gfx950 w/ ROCm7.0

PYTORCH_TEST_WITH_ROCM=1 python test/test_matmul_cuda.py -k test_blockwise -v Ran 452 tests in 22.698s
OK passed 111
This is same as before. (when PR 151360 was merged)

Pull Request resolved: https://github.com/pytorch/pytorch/pull/163127
Approved by: https://github.com/jeffdaily

Co-authored-by: Jeff Daily <jeff.daily@amd.com>

aten/src/ATen/cuda/CUDABlas.cpp

@@ -1954,8 +1954,8 @@ void scaled_gemm(
   #if ROCM_VERSION >= 70000
             if (at::detail::getCUDAHooks().isGPUArch({"gfx950"})) {
                 // TODO: add constraints based on hipblaslt internals
-                TORCH_CHECK((m % 32 == 0) && (n % 32 == 0) && (k % 32 == 0),
-                           "Matrix dimensions must be multiples of 32 for MX format. "
+                TORCH_CHECK((m % 16 == 0) && (n % 16 == 0) && (k % 128 == 0),
+                           "M, N must be multiples of 16 and K should be multiple of 128 for MX format. "
                            "Got m=", m, ", n=", n, ", k=", k);
             }
   #endif

aten/src/ATen/native/cuda/Blas.cpp

@@ -1138,9 +1138,14 @@ bool is_blockwise_1x16_scaling(const at::Tensor& t, const at::Tensor& scale) {
 bool is_blockwise_1x32_scaling(const at::Tensor& t, const at::Tensor& scale) {
   // TODO: We might want to enforce some structure on the shapes of the scale
   // tensors
-  return (isFloat8Type(t.scalar_type()) && scale.scalar_type() == at::kFloat8_e8m0fnu
-      && scale.numel() == round_up<int64_t>(t.size(0), 128) * round_up<int64_t>(ceil_div<int64_t>(t.size(1), 32), 4)
-      && scale.is_contiguous());
+  bool is_fp8_path = (isFloat8Type(t.scalar_type()) && scale.scalar_type() == at::kFloat8_e8m0fnu
+      && scale.numel() == round_up<int64_t>(t.size(0), 128) * round_up<int64_t>(ceil_div<int64_t>(t.size(1), 32), 4));
+  bool is_packed_fp4_path = false;
+#ifdef USE_ROCM
+  is_packed_fp4_path = (t.scalar_type() == ScalarType::Float4_e2m1fn_x2 && scale.scalar_type() == at::kFloat8_e8m0fnu
+      && scale.numel() == round_up<int64_t>(t.size(0), 128) * round_up<int64_t>(ceil_div<int64_t>(t.size(1) * 2, 32), 4));
+#endif
+  return (is_fp8_path || is_packed_fp4_path) && scale.is_contiguous();
 }
 
 bool is_blockwise_1x128_scaling(const at::Tensor& t, const at::Tensor& scale) {
@@ -1381,9 +1386,15 @@ _scaled_mm_out_cuda(const Tensor& mat1, const Tensor& mat2,
     TORCH_CHECK(at::detail::getCUDAHooks().isGPUArch({"gfx950"}),
                 "Block-wise scaling for Float8_e8m0fnu is only supported on gfx950");
 
-    TORCH_CHECK(mat1.size(0) % 32 == 0 && mat1.size(1) % 32 == 0 &&
-                mat2.size(0) % 32 == 0 && mat2.size(1) % 32 == 0,
-                "Matrix dimensions must be multiples of 32 for block-wise scaling");
+    int packed_factor = 1;
+    if (mat1.scalar_type() == ScalarType::Float4_e2m1fn_x2) {
+      // For float4 data type, each byte stores two 4-bit floating-point values,
+      // effectively packing two elements into one byte.
+      packed_factor = 2;
+    }
+    TORCH_CHECK(mat1.size(0) % 16 == 0 && (mat1.size(1) * packed_factor) % 128 == 0 &&
+                mat2.size(1) % 16 == 0,
+                "M, N must be multiples of 16 and K must be multiple of 128 for block-wise scaling");
 
     TORCH_CHECK(out.scalar_type() == ScalarType::BFloat16 ||
                 out.scalar_type() == ScalarType::Half,

test/test_matmul_cuda.py

@@ -926,7 +926,7 @@ def compute_error(x: torch.Tensor, y: torch.Tensor) -> torch.Tensor:
 # largest power of 2 representable in `torch.float8_e4m3fn`
 F8E4M3_LARGEST_POW2 = 8
 # largest power of 2 representable in `torch.float4_e2m1fn_x2`
-FP4E2M1FN_LARGEST_POW2 = 1.0
+FP4E2M1FN_LARGEST_POW2 = 2.0
 # max value of `torch.float8_e4m3fn` (448)
 F8E4M3_MAX_VAL = torch.finfo(torch.float8_e4m3fn).max
 # exponent bias of `torch.float8_e8m0fnu`
@@ -1746,8 +1746,12 @@ class TestFP8Matmul(TestCase):
 
         device = "cuda"
         M, K, N = mkn
-        if (recipe == "nvfp4" or recipe == "mxfp4") and K % 32 != 0:
-            raise unittest.SkipTest("K must be divisible by 32 for nvfp4/mxfp4 cublas gemm, skipping")
+        if recipe == "nvfp4" and K % 32 != 0:
+            raise unittest.SkipTest("K must be divisible by 32 for nvfp4 cublas gemm, skipping")
+
+        if torch.version.hip:
+            if not (M % 16 == 0 and K % 128 == 0 and N % 16 == 0):
+                raise unittest.SkipTest("M and N must be multiples of 16 and K must be multiple of 128 on ROCm, skipping")
 
         fp4_scaling_dtype = torch.float8_e8m0fnu if torch.version.hip else torch.float8_e4m3fn
         BLOCK_SIZE = 32 if torch.version.hip else (16 if recipe == "nvfp4" else 32)
@@ -1912,9 +1916,12 @@ class TestFP8Matmul(TestCase):
                 B = (B_ref.reshape(-1, BLOCK_SIZE) / B_scale.reshape(N * ceil_div(K, BLOCK_SIZE), 1).float()).reshape(N, K)
                 B = B.clamp(min=min_val, max=max_val).to(torch.float8_e4m3fn)
             else:  # nvfp4 # mxfp4
-                scale_func = data_to_mx_scale if recipe == "mxfp4" else data_to_nvfp4_scale
-                A_scale = scale_func(*([A_ref, BLOCK_SIZE] + recipe if recipe == "mxfp4" else [A_ref, BLOCK_SIZE]))
-                B_scale = scale_func(*([B_ref, BLOCK_SIZE] + recipe if recipe == "mxfp4" else [B_ref, BLOCK_SIZE]))
+                if recipe == "mxfp4":
+                    A_scale = data_to_mx_scale(A_ref, BLOCK_SIZE, recipe)
+                    B_scale = data_to_mx_scale(B_ref, BLOCK_SIZE, recipe)
+                else:
+                    A_scale = data_to_nvfp4_scale(A_ref, BLOCK_SIZE)
+                    B_scale = data_to_nvfp4_scale(B_ref, BLOCK_SIZE)
                 max_val = FP4_MAX_VAL
                 min_val = -1 * max_val
 
@@ -1925,7 +1932,7 @@ class TestFP8Matmul(TestCase):
                 B = B.clamp(min=min_val, max=max_val)
                 B = _bfloat16_to_float4_e2m1fn_x2(B)
 
-                approx_match_sqnr_target = 12.0 if torch.version.hip else 15.8
+                approx_match_sqnr_target = 15 if torch.version.hip else 15.8
 
         C_ref = A_ref @ B_ref.t()