[Kernel] Factor out epilogues from cutlass kernels

CMakeLists.txt

@@ -179,17 +179,17 @@ if(VLLM_GPU_LANG STREQUAL "CUDA")
     "csrc/quantization/gptq_marlin/gptq_marlin.cu"
     "csrc/quantization/gptq_marlin/gptq_marlin_repack.cu"
     "csrc/custom_all_reduce.cu"
-    "csrc/quantization/cutlass_w8a8/scaled_mm_dq_entry.cu"
-    "csrc/quantization/cutlass_w8a8/scaled_mm_dq_c2x.cu"
-    "csrc/quantization/cutlass_w8a8/scaled_mm_dq_c3x.cu")
+    "csrc/quantization/cutlass_w8a8/scaled_mm_entry.cu"
+    "csrc/quantization/cutlass_w8a8/scaled_mm_c2x.cu"
+    "csrc/quantization/cutlass_w8a8/scaled_mm_c3x.cu")
 
   #
   # The CUTLASS kernels for Hopper require sm90a to be enabled.
   # This is done via the below gencode option, BUT that creates kernels for both sm90 and sm90a.
   # That adds an extra 17MB to compiled binary, so instead we selectively enable it.
   if(${CMAKE_CUDA_COMPILER_VERSION} VERSION_GREATER 12.0)
     set_source_files_properties(
-          "csrc/quantization/cutlass_w8a8/scaled_mm_dq_c3x.cu"
+          "csrc/quantization/cutlass_w8a8/scaled_mm_c3x.cu"
           PROPERTIES
           COMPILE_FLAGS
           "-gencode arch=compute_90a,code=sm_90a")

benchmarks/cutlass_benchmarks/w8a8_benchmarks.py

@@ -76,11 +76,7 @@ def pytorch_fp8_impl_fast_accum(a: torch.tensor, b: torch.tensor,
 def cutlass_impl(a: torch.tensor, b: torch.tensor, scale_a: torch.tensor,
                  scale_b: torch.tensor,
                  out_dtype: torch.dtype) -> torch.tensor:
-    return ops.cutlass_scaled_mm_dq(a,
-                                    b,
-                                    scale_a,
-                                    scale_b,
-                                    out_dtype=out_dtype)
+    return ops.cutlass_scaled_mm(a, b, scale_a, scale_b, out_dtype=out_dtype)
 
 
 # bench

csrc/ops.h

@@ -90,9 +90,9 @@ torch::Tensor gptq_marlin_repack(torch::Tensor& b_q_weight, torch::Tensor& perm,
                                  int64_t size_k, int64_t size_n,
                                  int64_t num_bits);
 
-void cutlass_scaled_mm_dq(torch::Tensor& out, torch::Tensor const& a,
-                          torch::Tensor const& b, torch::Tensor const& a_scales,
-                          torch::Tensor const& b_scales);
+void cutlass_scaled_mm(torch::Tensor& out, torch::Tensor const& a,
+                       torch::Tensor const& b, torch::Tensor const& a_scales,
+                       torch::Tensor const& b_scales);
 
 #endif
 

csrc/quantization/cutlass_w8a8/scaled_mm_dq_c2x.cu → csrc/quantization/cutlass_w8a8/scaled_mm_c2x.cu

@@ -29,21 +29,14 @@
 using namespace cute;
 
 /*
-   This defines a quantized GEMM operation with dequantized output, similar to
-   torch._scaled_mm. It is defined using the CUTLASS 2.x API, and is used for
+   This file defines quantized GEMM operations using the CUTLASS 2.x API, for
    NVIDIA GPUs with SM versions prior to sm90 (Hopper).
 
-   A and B may be both either int8 or fp8_e4m3. A can be quantized per-tensor or
-   per-row. B can be quantized per-tensor or per-column.
-   Any combination of per-tensor and per-row or column is supported.
-   A and B must have symmetric quantization (zero point == 0).
-
-   So the GEMM operation is D = (a_scales * A) (b_scales * B), where the
-   scales are applied elementwise with numpy-style broadcasting.
-
-   ScaleA and ScaleB define the epilogue functions that apply the scales for
-   the A and B operands respectively. These scales may be either per-tensor or
-   per row or column.
+   Epilogue functions can be defined to post-process the output before it is
+   written to GPU memory.
+   Epilogues must contain a public type named EVTCompute of type Sm80EVT,
+   as well as a static prepare_args function that constructs an
+   EVTCompute::Arguments struct.
 */
 
 namespace {
@@ -83,27 +76,25 @@ struct enable_sm89_to_sm90 : Kernel {
   }
 };
 
-template <typename Arch, template <typename> typename ArchGuard,
-          typename ElementAB_, typename ElementD_, typename TileShape,
-          typename WarpShape, typename InstructionShape, int32_t MainLoopStages>
-struct cutlass_2x_gemm {
-  using ElementAB = ElementAB_;
-  using ElementD = ElementD_;
-
-  using ElementAcc =
-      typename std::conditional<std::is_same_v<ElementAB, int8_t>, int32_t,
-                                float>::type;
+/*
+   This epilogue function defines a quantized GEMM operation similar to
+   torch._scaled_mm.
 
-  using Operator =
-      typename std::conditional<std::is_same_v<ElementAB, int8_t>,
-                                cutlass::arch::OpMultiplyAddSaturate,
-                                cutlass::arch::OpMultiplyAdd>::type;
+   A and B may be both either int8 or fp8_e4m3. A can be quantized per-tensor or
+   per-row. B can be quantized per-tensor or per-column.
+   Any combination of per-tensor and per-row or column is supported.
+   A and B must have symmetric quantization (zero point == 0).
 
-  using OutputTileThreadMap =
-      cutlass::epilogue::threadblock::OutputTileThreadLayout<
-          TileShape, WarpShape, float, 4, 1 /* epilogue stages */
-          >;
+   So the GEMM operation is D = (a_scales * A) (b_scales * B), where the
+   scales are applied elementwise with numpy-style broadcasting.
 
+   ScaleA and ScaleB define the epilogue functions that apply the scales for
+   the A and B operands respectively. These scales may be either per-tensor or
+   per row or column.
+*/
+template <typename ElementD, typename OutputTileThreadMap>
+struct ScaledEpilogue {
+ private:
   using Accum = cutlass::epilogue::threadblock::VisitorAccFetch;
 
   using ScaleA = cutlass::epilogue::threadblock::VisitorColOrScalarBroadcast<
@@ -123,14 +114,56 @@ struct cutlass_2x_gemm {
       cutlass::multiplies, ElementD, float,
       cutlass::FloatRoundStyle::round_to_nearest>;
 
-  using EVTCompute1 =
+ public:
+  using EVTCompute =
       cutlass::epilogue::threadblock::Sm80EVT<Compute1, ScaleA, EVTCompute0>;
+  using ArgumentType = typename EVTCompute::Arguments;
+
+  static ArgumentType prepare_args(torch::Tensor const& a_scales,
+                                   torch::Tensor const& b_scales) {
+    using ScaleAArgs = typename ScaleA::Arguments;
+    using ScaleBArgs = typename ScaleB::Arguments;
+
+    ScaleBArgs b_args{b_scales.data_ptr<float>(), b_scales.numel() != 1, {}};
+    ScaleAArgs a_args{a_scales.data_ptr<float>(), a_scales.numel() != 1, {}};
+
+    typename EVTCompute0::Arguments evt0_compute_args{b_args};
+
+    typename EVTCompute::Arguments evt_compute_args{a_args, evt0_compute_args};
+    return evt_compute_args;
+  }
+};
+
+template <typename Arch, template <typename> typename ArchGuard,
+          typename ElementAB_, typename ElementD_,
+          template <typename, typename> typename Epilogue_, typename TileShape,
+          typename WarpShape, typename InstructionShape, int32_t MainLoopStages>
+struct cutlass_2x_gemm {
+  using ElementAB = ElementAB_;
+  using ElementD = ElementD_;
+
+  using ElementAcc =
+      typename std::conditional<std::is_same_v<ElementAB, int8_t>, int32_t,
+                                float>::type;
+
+  using Operator =
+      typename std::conditional<std::is_same_v<ElementAB, int8_t>,
+                                cutlass::arch::OpMultiplyAddSaturate,
+                                cutlass::arch::OpMultiplyAdd>::type;
+
+  using OutputTileThreadMap =
+      cutlass::epilogue::threadblock::OutputTileThreadLayout<
+          TileShape, WarpShape, float, 4, 1 /* epilogue stages */
+          >;
+
+  using Epilogue = Epilogue_<ElementD, OutputTileThreadMap>;
+  using EVTCompute = typename Epilogue::EVTCompute;
 
   using D = cutlass::epilogue::threadblock::VisitorAuxStore<
       OutputTileThreadMap, ElementD, cutlass::FloatRoundStyle::round_to_nearest,
       Stride<int64_t, Int<1>, Int<0>>>;
 
-  using EVTD = cutlass::epilogue::threadblock::Sm80EVT<D, EVTCompute1>;
+  using EVTD = cutlass::epilogue::threadblock::Sm80EVT<D, EVTCompute>;
 
   // clang-format off
   using RowMajor = typename cutlass::layout::RowMajor;
@@ -153,11 +186,10 @@ struct cutlass_2x_gemm {
   using Op = cutlass::gemm::device::GemmUniversalAdapter<KernelType>;
 };
 
-template <typename Gemm>
-void cutlass_scaled_mm_dq_dispatcher(torch::Tensor& out, torch::Tensor const& a,
-                                     torch::Tensor const& b,
-                                     torch::Tensor const& a_scales,
-                                     torch::Tensor const& b_scales) {
+template <typename Gemm, typename... EpilogueArgs>
+void cutlass_gemm_caller(torch::Tensor& out, torch::Tensor const& a,
+                         torch::Tensor const& b,
+                         EpilogueArgs&&... epilogue_params) {
   using ElementAB = typename Gemm::ElementAB;
   using ElementD = typename Gemm::ElementD;
 
@@ -177,23 +209,14 @@ void cutlass_scaled_mm_dq_dispatcher(torch::Tensor& out, torch::Tensor const& a,
   auto b_ptr = static_cast<ElementAB const*>(b.data_ptr());
   auto c_ptr = static_cast<ElementD*>(out.data_ptr());
 
-  auto a_scales_ptr = a_scales.data_ptr<float>();
-  auto b_scales_ptr = b_scales.data_ptr<float>();
-
-  using ScaleAArgs = typename Gemm::ScaleA::Arguments;
-  using ScaleBArgs = typename Gemm::ScaleB::Arguments;
-
-  ScaleBArgs b_args{b_scales.data_ptr<float>(), b_scales.numel() != 1, {}};
-  ScaleAArgs a_args{a_scales.data_ptr<float>(), a_scales.numel() != 1, {}};
-
-  typename Gemm::EVTCompute0::Arguments evt0_compute_args{b_args};
-
-  typename Gemm::EVTCompute1::Arguments evt1_compute_args{a_args,
-                                                          evt0_compute_args};
   typename Gemm::D::Arguments d_args{c_ptr, c_stride};
 
+  using Epilogue = typename Gemm::Epilogue;
+  auto evt_args =
+      Epilogue::prepare_args(std::forward<EpilogueArgs>(epilogue_params)...);
+
   typename Gemm::EVTD::Arguments epilogue_args{
-      evt1_compute_args,
+      evt_args,
       d_args,
   };
 
@@ -229,10 +252,10 @@ void cutlass_scaled_mm_dq_dispatcher(torch::Tensor& out, torch::Tensor const& a,
 
 }  // namespace
 
-void cutlass_scaled_mm_dq_sm75(torch::Tensor& out, torch::Tensor const& a,
-                               torch::Tensor const& b,
-                               torch::Tensor const& a_scales,
-                               torch::Tensor const& b_scales) {
+void cutlass_scaled_mm_sm75(torch::Tensor& out, torch::Tensor const& a,
+                            torch::Tensor const& b,
+                            torch::Tensor const& a_scales,
+                            torch::Tensor const& b_scales) {
   TORCH_CHECK(a.dtype() == torch::kInt8);
   TORCH_CHECK(b.dtype() == torch::kInt8);
   TORCH_CHECK(a_scales.dtype() == torch::kFloat32);
@@ -243,23 +266,23 @@ void cutlass_scaled_mm_dq_sm75(torch::Tensor& out, torch::Tensor const& a,
   using InstructionShape = typename cutlass::gemm::GemmShape<8, 8, 16>;
 
   if (out.dtype() == torch::kBFloat16) {
-    return cutlass_scaled_mm_dq_dispatcher<cutlass_2x_gemm<
+    return cutlass_gemm_caller<cutlass_2x_gemm<
         cutlass::arch::Sm75, enable_sm75_to_sm80, int8_t, cutlass::bfloat16_t,
-        TileShape, WarpShape, InstructionShape, 2>>(out, a, b, a_scales,
-                                                    b_scales);
+        ScaledEpilogue, TileShape, WarpShape, InstructionShape, 2>>(
+        out, a, b, a_scales, b_scales);
   } else {
     TORCH_CHECK(out.dtype() == torch::kFloat16);
-    return cutlass_scaled_mm_dq_dispatcher<cutlass_2x_gemm<
+    return cutlass_gemm_caller<cutlass_2x_gemm<
         cutlass::arch::Sm75, enable_sm75_to_sm80, int8_t, cutlass::half_t,
-        TileShape, WarpShape, InstructionShape, 2>>(out, a, b, a_scales,
-                                                    b_scales);
+        ScaledEpilogue, TileShape, WarpShape, InstructionShape, 2>>(
+        out, a, b, a_scales, b_scales);
   }
 }
 
-void cutlass_scaled_mm_dq_sm80(torch::Tensor& out, torch::Tensor const& a,
-                               torch::Tensor const& b,
-                               torch::Tensor const& a_scales,
-                               torch::Tensor const& b_scales) {
+void cutlass_scaled_mm_sm80(torch::Tensor& out, torch::Tensor const& a,
+                            torch::Tensor const& b,
+                            torch::Tensor const& a_scales,
+                            torch::Tensor const& b_scales) {
   TORCH_CHECK(a.dtype() == torch::kInt8);
   TORCH_CHECK(b.dtype() == torch::kInt8);
   TORCH_CHECK(a_scales.dtype() == torch::kFloat32);
@@ -270,23 +293,23 @@ void cutlass_scaled_mm_dq_sm80(torch::Tensor& out, torch::Tensor const& a,
   using InstructionShape = typename cutlass::gemm::GemmShape<16, 8, 32>;
 
   if (out.dtype() == torch::kBFloat16) {
-    return cutlass_scaled_mm_dq_dispatcher<cutlass_2x_gemm<
+    return cutlass_gemm_caller<cutlass_2x_gemm<
         cutlass::arch::Sm80, enable_sm80_to_sm89, int8_t, cutlass::bfloat16_t,
-        TileShape, WarpShape, InstructionShape, 5>>(out, a, b, a_scales,
-                                                    b_scales);
+        ScaledEpilogue, TileShape, WarpShape, InstructionShape, 5>>(
+        out, a, b, a_scales, b_scales);
   } else {
     TORCH_CHECK(out.dtype() == torch::kFloat16);
-    return cutlass_scaled_mm_dq_dispatcher<cutlass_2x_gemm<
+    return cutlass_gemm_caller<cutlass_2x_gemm<
         cutlass::arch::Sm80, enable_sm80_to_sm89, int8_t, cutlass::half_t,
-        TileShape, WarpShape, InstructionShape, 5>>(out, a, b, a_scales,
-                                                    b_scales);
+        ScaledEpilogue, TileShape, WarpShape, InstructionShape, 5>>(
+        out, a, b, a_scales, b_scales);
   }
 }
 
-void cutlass_scaled_mm_dq_sm89(torch::Tensor& out, torch::Tensor const& a,
-                               torch::Tensor const& b,
-                               torch::Tensor const& a_scales,
-                               torch::Tensor const& b_scales) {
+void cutlass_scaled_mm_sm89(torch::Tensor& out, torch::Tensor const& a,
+                            torch::Tensor const& b,
+                            torch::Tensor const& a_scales,
+                            torch::Tensor const& b_scales) {
   using TileShape = typename cutlass::gemm::GemmShape<128, 128, 64>;
   using WarpShape = typename cutlass::gemm::GemmShape<64, 64, 64>;
   using InstructionShape = typename cutlass::gemm::GemmShape<16, 8, 32>;
@@ -298,32 +321,32 @@ void cutlass_scaled_mm_dq_sm89(torch::Tensor& out, torch::Tensor const& a,
     TORCH_CHECK(b.dtype() == torch::kInt8);
 
     if (out.dtype() == torch::kBFloat16) {
-      return cutlass_scaled_mm_dq_dispatcher<cutlass_2x_gemm<
+      return cutlass_gemm_caller<cutlass_2x_gemm<
           cutlass::arch::Sm89, enable_sm89_to_sm90, int8_t, cutlass::bfloat16_t,
-          TileShape, WarpShape, InstructionShape, 5>>(out, a, b, a_scales,
-                                                      b_scales);
+          ScaledEpilogue, TileShape, WarpShape, InstructionShape, 5>>(
+          out, a, b, a_scales, b_scales);
     } else {
       assert(out.dtype() == torch::kFloat16);
-      return cutlass_scaled_mm_dq_dispatcher<cutlass_2x_gemm<
+      return cutlass_gemm_caller<cutlass_2x_gemm<
           cutlass::arch::Sm89, enable_sm89_to_sm90, int8_t, cutlass::half_t,
-          TileShape, WarpShape, InstructionShape, 5>>(out, a, b, a_scales,
-                                                      b_scales);
+          ScaledEpilogue, TileShape, WarpShape, InstructionShape, 5>>(
+          out, a, b, a_scales, b_scales);
     }
   } else {
     TORCH_CHECK(a.dtype() == torch::kFloat8_e4m3fn);
     TORCH_CHECK(b.dtype() == torch::kFloat8_e4m3fn);
 
     if (out.dtype() == torch::kBFloat16) {
-      return cutlass_scaled_mm_dq_dispatcher<cutlass_2x_gemm<
+      return cutlass_gemm_caller<cutlass_2x_gemm<
           cutlass::arch::Sm89, enable_sm89_to_sm90, cutlass::float_e4m3_t,
-          cutlass::bfloat16_t, TileShape, WarpShape, InstructionShape, 5>>(
-          out, a, b, a_scales, b_scales);
+          cutlass::bfloat16_t, ScaledEpilogue, TileShape, WarpShape,
+          InstructionShape, 5>>(out, a, b, a_scales, b_scales);
     } else {
       TORCH_CHECK(out.dtype() == torch::kFloat16);
-      return cutlass_scaled_mm_dq_dispatcher<cutlass_2x_gemm<
+      return cutlass_gemm_caller<cutlass_2x_gemm<
           cutlass::arch::Sm89, enable_sm89_to_sm90, cutlass::float_e4m3_t,
-          cutlass::half_t, TileShape, WarpShape, InstructionShape, 5>>(
-          out, a, b, a_scales, b_scales);
+          cutlass::half_t, ScaledEpilogue, TileShape, WarpShape,
+          InstructionShape, 5>>(out, a, b, a_scales, b_scales);
     }
   }
 }