Add device type meta support for CutlassNvfp4GroupedMmaOp::evaluate

CMakeLists.txt

@@ -557,7 +557,7 @@ target_link_libraries(codegen_internal PUBLIC
 )
 if (BUILD_CUTLASS AND CMAKE_CUDA_COMPILER_VERSION VERSION_GREATER_EQUAL 12.8)
   target_link_libraries(codegen_internal PUBLIC nvf_cutlass)
-  target_compile_definitions(codegen_internal PRIVATE "-DNVFUSER_CUTLASS_KERNEL_ENABLED")
+  target_compile_definitions(codegen_internal PUBLIC "-DNVFUSER_CUTLASS_KERNEL_ENABLED")
 endif()
 
 target_link_libraries(codegen_internal PUBLIC LLVM_JIT)

csrc/ir/composite_nodes.cpp

@@ -1713,7 +1713,6 @@ std::string CutlassNvfp4GroupedMmaOp::toInlineString(int indent_size) const {
 std::vector<PolymorphicValue> CutlassNvfp4GroupedMmaOp::evaluate(
     const ExpressionEvaluator& ee,
     const std::vector<PolymorphicValue>& inputs) const {
-#if NVFUSER_CUTLASS_KERNEL_ENABLED
   const auto& mat1 = inputs[0].as<at::Tensor>();
   const auto& mat2 = inputs[1].as<at::Tensor>();
   const auto& scale1 = inputs[2].as<at::Tensor>();
@@ -1722,6 +1721,29 @@ std::vector<PolymorphicValue> CutlassNvfp4GroupedMmaOp::evaluate(
   const auto& problem_sizes = inputs[5].as<at::Tensor>();
   const auto& expert_offsets = inputs[6].as<at::Tensor>();
   const auto& sf_offsets = inputs[7].as<at::Tensor>();
+
+  // Meta-device fast path outside of torch version guard
+  if (mat1.is_meta() || mat2.is_meta() || scale1.is_meta() ||
+      scale2.is_meta() || alpha.is_meta() || problem_sizes.is_meta() ||
+      expert_offsets.is_meta() || sf_offsets.is_meta()) {
+    // For nvfp4_scaled_grouped_mm, the output shape is [M, N]
+    // where M = mat1.size(0) and N = mat2.size(1)
+    std::vector<int64_t> result_sizes = {mat1.size(0), mat2.size(1)};
+
+    at::ScalarType out_dtype = data_type_to_aten(out()->dtype());
+    auto options =
+        mat1.options().device(c10::Device(c10::kMeta)).dtype(out_dtype);
+    at::Tensor result = at::empty(result_sizes, options);
+
+    if (const auto rfactor_did_idx = getRFactorDeviceDimensionIndex(out());
+        rfactor_did_idx != -1) {
+      result = result.unsqueeze(rfactor_did_idx);
+    }
+
+    return {result};
+  }
+
+#if NVFUSER_CUTLASS_KERNEL_ENABLED
   NVF_CHECK(
       mat1.scalar_type() == at::ScalarType::Float4_e2m1fn_x2 &&
       mat2.scalar_type() == at::ScalarType::Float4_e2m1fn_x2);

tests/cpp/test_meta.cpp

@@ -533,4 +533,140 @@ TEST_F(MetaTest, Matmul1D) {
   EXPECT_EQ(meta_out.strides(), real_out.strides());
 }
 
+// Test CutlassNvfp4GroupedMmaOp with meta device
+TEST_F(MetaTest, CutlassNvfp4GroupedMma) {
+#if NVFUSER_CUTLASS_KERNEL_ENABLED
+  auto fusion = std::make_unique<Fusion>();
+  FusionGuard fg(fusion.get());
+
+  // Choose an example where all M, N, K, and K/2 are different:
+  //   M = 128, N = 80, K = 192, K/2 = 96
+  // Shapes:
+  //   mat1: [M, K/2]       = [128, 96]   (packed FP4)
+  //   mat2: [G, N, K/2]    = [4, 80, 96] (packed FP4)
+  //   output: [M, N]       = [128, 80]
+  // Note: Use unpacked type Float4_e2m1fn for fusion definition
+  auto mat1 = makeContigConcreteTensor({128, 96}, DataType::Float4_e2m1fn);
+  auto mat2 =
+      makeContigConcreteTensor({4, 80, 96}, DataType::Float4_e2m1fn);
+  // Block-scaling factors have last dim K / 16 = 192 / 16 = 12
+  auto scale1 = makeContigConcreteTensor({128, 12}, DataType::Float8_e4m3fn);
+  auto scale2 = makeContigConcreteTensor({4, 80, 12}, DataType::Float8_e4m3fn);
+  auto alpha = makeContigConcreteTensor({4}, DataType::Float);
+  auto problem_sizes = makeContigConcreteTensor({4, 3}, DataType::Index);
+  auto expert_offsets = makeContigConcreteTensor({4}, DataType::Index);
+  auto sf_offsets = makeContigConcreteTensor({4}, DataType::Index);
+
+  fusion->addInput(mat1);
+  fusion->addInput(mat2);
+  fusion->addInput(scale1);
+  fusion->addInput(scale2);
+  fusion->addInput(alpha);
+  fusion->addInput(problem_sizes);
+  fusion->addInput(expert_offsets);
+  fusion->addInput(sf_offsets);
+
+  auto result = cutlass_nvfp4_grouped_mm(
+      mat1,
+      mat2,
+      scale1,
+      scale2,
+      alpha,
+      problem_sizes,
+      expert_offsets,
+      sf_offsets,
+      DataType::BFloat16);
+  fusion->addOutput(result);
+
+  // Create real inputs with appropriate data types
+  auto options_uint8 =
+      at::TensorOptions().dtype(torch::kUInt8).device(at::kCUDA, 0);
+  auto options_fp4 =
+      at::TensorOptions().dtype(at::kFloat4_e2m1fn_x2).device(at::kCUDA, 0);
+  auto options_fp8 =
+      at::TensorOptions().dtype(at::kFloat8_e4m3fn).device(at::kCUDA, 0);
+  auto options_fp32 =
+      at::TensorOptions().dtype(at::kFloat).device(at::kCUDA, 0);
+  auto options_int = at::TensorOptions().dtype(at::kInt).device(at::kCUDA, 0);
+
+  // FP4 tensors must be created as UInt8 and viewed as Float4
+  at::Tensor mat1_input =
+      at::randint(0, 256, {128, 96}, options_uint8).view(at::kFloat4_e2m1fn_x2);
+  at::Tensor mat2_input = at::randint(0, 256, {4, 80, 96}, options_uint8)
+                              .view(at::kFloat4_e2m1fn_x2);
+  // FP8 tensors can be created from FP32 tensors
+  at::Tensor scale1_input =
+      at::randn({128, 12}, options_fp32).to(at::kFloat8_e4m3fn);
+  at::Tensor scale2_input =
+      at::randn({4, 80, 12}, options_fp32).to(at::kFloat8_e4m3fn);
+  at::Tensor alpha_input = at::ones({4}, options_fp32);
+  at::Tensor problem_sizes_input = at::tensor(
+      {32, 80, 192, 32, 80, 192, 32, 80, 192, 32, 80, 192},
+      options_int).reshape({4, 3});
+  at::Tensor expert_offsets_input = at::tensor({0, 32, 64, 96}, options_int);
+  at::Tensor sf_offsets_input = at::tensor({0, 32, 64, 96}, options_int);
+
+  // CUDA path
+  ExpressionEvaluator ee_cuda;
+  ee_cuda.bind(fusion->inputs().at(0), mat1_input);
+  ee_cuda.bind(fusion->inputs().at(1), mat2_input);
+  ee_cuda.bind(fusion->inputs().at(2), scale1_input);
+  ee_cuda.bind(fusion->inputs().at(3), scale2_input);
+  ee_cuda.bind(fusion->inputs().at(4), alpha_input);
+  ee_cuda.bind(fusion->inputs().at(5), problem_sizes_input);
+  ee_cuda.bind(fusion->inputs().at(6), expert_offsets_input);
+  ee_cuda.bind(fusion->inputs().at(7), sf_offsets_input);
+  auto real_out = ee_cuda.evaluate(fusion->outputs().at(0)).as<at::Tensor>();
+
+  // Meta evaluation
+  ExpressionEvaluator ee_meta;
+  auto meta_mat1 = at::empty_strided(
+      mat1_input.sizes(), mat1_input.strides(), options_fp4.device(at::kMeta));
+  auto meta_mat2 = at::empty_strided(
+      mat2_input.sizes(), mat2_input.strides(), options_fp4.device(at::kMeta));
+  auto meta_scale1 = at::empty_strided(
+      scale1_input.sizes(),
+      scale1_input.strides(),
+      options_fp8.device(at::kMeta));
+  auto meta_scale2 = at::empty_strided(
+      scale2_input.sizes(),
+      scale2_input.strides(),
+      options_fp8.device(at::kMeta));
+  auto meta_alpha = at::empty_strided(
+      alpha_input.sizes(),
+      alpha_input.strides(),
+      options_fp32.device(at::kMeta));
+  auto meta_problem_sizes = at::empty_strided(
+      problem_sizes_input.sizes(),
+      problem_sizes_input.strides(),
+      options_int.device(at::kMeta));
+  auto meta_expert_offsets = at::empty_strided(
+      expert_offsets_input.sizes(),
+      expert_offsets_input.strides(),
+      options_int.device(at::kMeta));
+  auto meta_sf_offsets = at::empty_strided(
+      sf_offsets_input.sizes(),
+      sf_offsets_input.strides(),
+      options_int.device(at::kMeta));
+
+  ee_meta.bind(fusion->inputs().at(0), meta_mat1);
+  ee_meta.bind(fusion->inputs().at(1), meta_mat2);
+  ee_meta.bind(fusion->inputs().at(2), meta_scale1);
+  ee_meta.bind(fusion->inputs().at(3), meta_scale2);
+  ee_meta.bind(fusion->inputs().at(4), meta_alpha);
+  ee_meta.bind(fusion->inputs().at(5), meta_problem_sizes);
+  ee_meta.bind(fusion->inputs().at(6), meta_expert_offsets);
+  ee_meta.bind(fusion->inputs().at(7), meta_sf_offsets);
+  auto meta_out = ee_meta.evaluate(fusion->outputs().at(0)).as<at::Tensor>();
+
+  // Checks
+  EXPECT_TRUE(meta_out.is_meta());
+  EXPECT_EQ(meta_out.scalar_type(), at::kBFloat16);
+  EXPECT_EQ(meta_out.sizes(), real_out.sizes());
+  EXPECT_EQ(meta_out.strides(), real_out.strides());
+#else
+  GTEST_SKIP() << "Test requires CUTLASS support";
+#endif
+}
+
 } // namespace nvfuser