Enhancing fused_transpose_split_quant with fp8 capability. (PaddlePaddle#74471)

A-nnonymous · Enigmatisms · commit c91fe437c6de · 2025-08-11T12:57:57.000Z
* Enhanced fused_transpose_split_quant with fp8 capability.

* optimize performance.

* Clean comment

* clean miscs

* Fix example
diff --git a/paddle/phi/infermeta/fusion.cc b/paddle/phi/infermeta/fusion.cc
@@ -2421,16 +2421,17 @@ void FusedMultiTransformerInt8InferMeta(
 }
 
 void FusedTransposeSplitQuantInferMeta(const MetaTensor& x,
+                                       const MetaTensor& input_scales,
                                        const IntArray& tokens_per_expert,
                                        bool pow_2_scales,
                                        std::vector<MetaTensor*> outs,
                                        std::vector<MetaTensor*> scales) {
   PADDLE_ENFORCE_EQ(
-      x.dtype(),
-      DataType::BFLOAT16,
-      common::errors::InvalidArgument(
-          "The dtype of Input(x) must be BFLOAT16, but received %s",
-          x.dtype()));
+      x.dtype() == DataType::BFLOAT16 || x.dtype() == DataType::FLOAT8_E4M3FN,
+      true,
+      common::errors::InvalidArgument("The dtype of Input(x) must be BFLOAT16 "
+                                      "or FLOAT8_E4M3FN, but received %s",
+                                      x.dtype()));
 
   auto x_dims = x.dims();
 
diff --git a/paddle/phi/infermeta/fusion.h b/paddle/phi/infermeta/fusion.h
@@ -669,6 +669,7 @@ void FusedMultiTransformerInt8InferMeta(
     MetaTensor* out);
 
 void FusedTransposeSplitQuantInferMeta(const MetaTensor& x,
+                                       const MetaTensor& input_scales,
                                        const IntArray& tokens_per_expert,
                                        bool pow_2_scales,
                                        std::vector<MetaTensor*> outs,
diff --git a/paddle/phi/kernels/fusion/gpu/fused_transpose_split_quant_kernel.cu b/paddle/phi/kernels/fusion/gpu/fused_transpose_split_quant_kernel.cu
@@ -29,43 +29,62 @@ struct __align__(sizeof(T) * VecSize) VecType {
   }
 };
 
-template <int VecSize>
-__device__ void BlockLoad(const phi::bfloat16* input,
+template <typename InT, int VecSize>
+__device__ void BlockLoad(const InT* input,
+                          const float* input_scales,
                           __nv_bfloat16 x[8][4],
-                          size_t K) {
+                          size_t K,
+                          size_t k_scaled) {
+  constexpr bool need_dequant = std::is_same_v<InT, phi::dtype::float8_e4m3fn>;
+
+#pragma unroll
   for (uint32_t i = 0; i < 8; i++) {
-    size_t off_m = blockIdx.x * size_t(128) + threadIdx.y + i * 16;
-    size_t off_k = blockIdx.y * 128 + threadIdx.x * VecSize;
-    size_t offset = off_m * K + off_k;
+    const uint32_t local_off_M = threadIdx.y + i * 16;
+    const uint32_t off_m = blockIdx.x * 128 + local_off_M;
+    const uint32_t off_k = blockIdx.y * 128 + threadIdx.x * VecSize;
+    const size_t offset = off_m * K + off_k;
+
+    float scale;
+    if constexpr (need_dequant) {
+      const uint32_t m_base = blockIdx.x * 128;
+      const uint32_t m_stride = k_scaled;
+      scale = input_scales[off_m * m_stride + blockIdx.y];
+    }
 
+#pragma unroll
     for (uint32_t j = 0; j < 4; j += VecSize) {
-      if (off_k + j * 32 < K) {
-        size_t idx = offset + j * 32;
-        using LoadT = VecType<__nv_bfloat16, VecSize>;
-        LoadT data = *reinterpret_cast<const LoadT*>(input + idx);
-        for (uint32_t k = 0; k < VecSize; k++) {
-          x[i][j + k] = data[k];
+      const size_t idx = offset + j * 32;
+      using LoadT = VecType<InT, VecSize>;
+      LoadT data = *reinterpret_cast<const LoadT*>(input + idx);
+#pragma unroll
+      for (uint32_t k = 0; k < VecSize; k++) {
+        if constexpr (need_dequant) {
+          x[i][j + k] = __float2bfloat16(static_cast<float>(data[k]) * scale);
+        } else {
+          x[i][j + k] = (*reinterpret_cast<__nv_bfloat16*>(&data[k]));
         }
       }
     }
   }
 }
-
 template <bool Pow2Scales>
 __device__ void BlockColumnScale(const __nv_bfloat16 x[8][4],
-                                 float col_scale[128],
+                                 float scales[128],
                                  __nv_bfloat16* shm) {
   // reduce [(8), 16, 32, 4] => [16, 32, 4]
   __nv_bfloat16 warp_max[4];
+#pragma unroll
   for (uint32_t i = 0; i < 8; i++) {
+#pragma unroll
     for (uint32_t j = 0; j < 4; j++) {
-      __nv_bfloat16 t = BF16_ABS(x[i][j]);
+      const __nv_bfloat16 t = BF16_ABS(x[i][j]);
       warp_max[j] = i == 0 ? t : BF16_MAX(warp_max[j], t);
     }
   }
 
   // reduce [(16), 32, 4] => [8, 32, 4]
   if (threadIdx.y >= 8) {
+#pragma unroll
     for (uint32_t j = 0; j < 4; j++) {
       shm[(threadIdx.y - 8) * 128 + threadIdx.x + j * 32] = warp_max[j];
     }
@@ -75,8 +94,9 @@ __device__ void BlockColumnScale(const __nv_bfloat16 x[8][4],
   // reduce [(8), 32, 4] => [32, 4]
   for (uint32_t offset = 8; offset > 0; offset /= 2) {
     if (threadIdx.y < offset) {
+#pragma unroll
       for (uint32_t j = 0; j < 4; j++) {
-        __nv_bfloat16 other =
+        const __nv_bfloat16 other =
             offset == 8
                 ? warp_max[j]
                 : shm[(threadIdx.y + offset) * 128 + threadIdx.x + j * 32];
@@ -85,7 +105,7 @@ __device__ void BlockColumnScale(const __nv_bfloat16 x[8][4],
         if (offset > 1) {
           shm[threadIdx.y * 128 + threadIdx.x + j * 32] = next_val;
         } else {
-          col_scale[threadIdx.x + j * 32] =
+          scales[threadIdx.x + j * 32] =
               ComputeScale<__nv_bfloat16, __nv_fp8_e4m3, Pow2Scales>(
                   static_cast<float>(next_val), 0.0f);
         }
@@ -98,7 +118,7 @@ __device__ void BlockColumnScale(const __nv_bfloat16 x[8][4],
 template <typename OutT, int VecSize>
 __device__ void BlockStoreScale(float* scale,
                                 size_t off_m,
-                                float col_scale[128],
+                                float scales[128],
                                 size_t K) {
   if (threadIdx.y < 4) {
     uint32_t off = threadIdx.y * 32 + threadIdx.x;
@@ -107,10 +127,10 @@ __device__ void BlockStoreScale(float* scale,
     } else if constexpr (VecSize == 2) {
       off = (off / 64) * 64 + (off % 2) * 32 + (off % 64) / 2;
     }
-    float scale_out = 1.0f / col_scale[off];
-    size_t idx_y = blockIdx.x - off_m / 128;
-    size_t idx_x = blockIdx.y * 128 + threadIdx.y * 32 + threadIdx.x;
-    size_t idx = idx_y * K + idx_x;
+    float scale_out = 1.0f / scales[off];
+    const size_t idx_y = blockIdx.x - off_m / 128;
+    const size_t idx_x = blockIdx.y * 128 + threadIdx.y * 32 + threadIdx.x;
+    const size_t idx = idx_y * K + idx_x;
     if (idx_x < K) {
       scale[idx] = scale_out;
     }
@@ -123,14 +143,16 @@ __device__ void BlockStoreOut(OutT* out,
                               size_t cur_tokens,
                               const OutT shm[128][129],
                               size_t K) {
+#pragma unroll
   for (uint32_t i = 0; i < 8; i++) {
-    size_t idx_m = blockIdx.x * size_t(128) + threadIdx.x * 4;
-    size_t idx_k = blockIdx.y * 128 + threadIdx.y + i * 16;
-    size_t idx = idx_k * cur_tokens + (idx_m - off_m);
+    const size_t idx_m = blockIdx.x * size_t(128) + threadIdx.x * 4;
+    const size_t idx_k = blockIdx.y * 128 + threadIdx.y + i * 16;
+    const size_t idx = idx_k * cur_tokens + (idx_m - off_m);
 
     if (idx_k < K) {
       using StoreT = VecType<OutT, VecSize>;
       StoreT data;
+#pragma unroll
       for (uint32_t j = 0; j < VecSize; j++) {
         data[j] = shm[i * 16 + threadIdx.y][threadIdx.x * 4 + j];
       }
@@ -139,23 +161,27 @@ __device__ void BlockStoreOut(OutT* out,
   }
 }
 
-template <typename OutT, bool Pow2Scales, int VecSize>
+template <typename InT, typename OutT, bool Pow2Scales, int VecSize>
 __global__ void __launch_bounds__(512)
-    FusedTransposeSplitQuantKernel(const phi::bfloat16* __restrict__ input,
+    FusedTransposeSplitQuantKernel(const InT* __restrict__ input,
+                                   const float* __restrict__ input_scales,
                                    int64_t* __restrict__ meta,
                                    size_t num_experts,
-                                   size_t K) {
+                                   size_t K,
+                                   size_t k_scaled) {
   __shared__ OutT shm[128][129];
+  __shared__ size_t expert_info[2];
+  __shared__ float scales[128];  // May be reused? Is it worthy?
+
   int64_t* tokens_per_expert = meta;
   OutT** out_ptrs = reinterpret_cast<OutT**>(meta + num_experts);
   float** scale_ptrs = reinterpret_cast<float**>(meta + num_experts * 2);
 
   // 1. Load 128x128 elements from input
   __nv_bfloat16 x[8][4];
-  BlockLoad<VecSize>(input, x, K);
+  BlockLoad<InT, VecSize>(input, input_scales, x, K, k_scaled);
 
   // 2. Get expert index and offset of the current block
-  __shared__ size_t expert_info[2];
   if (threadIdx.x == 0 && threadIdx.y == 0) {
     size_t idx_m = blockIdx.x * size_t(128);
     size_t off_m = 0, next_off_m = 0;
@@ -172,21 +198,23 @@ __global__ void __launch_bounds__(512)
   }
 
   // 3. Calculate scale along the column
-  __shared__ float col_scale[128];
   BlockColumnScale<Pow2Scales>(
-      x, col_scale, reinterpret_cast<__nv_bfloat16*>(shm));
+      x, scales, reinterpret_cast<__nv_bfloat16*>(shm));
 
   // 4. Store scale
   const size_t expert_idx = expert_info[0];
   const size_t off_m = expert_info[1];
-  BlockStoreScale<OutT, VecSize>(scale_ptrs[expert_idx], off_m, col_scale, K);
+  BlockStoreScale<OutT, VecSize>(scale_ptrs[expert_idx], off_m, scales, K);
 
-  // 5. Scale x and save into shared memory with transposed layout
+// 5. Scale x and save into shared memory with transposed layout
+#pragma unroll
   for (uint32_t i = 0; i < 8; i++) {
+#pragma unroll
     for (uint32_t j = 0; j < 4; j += VecSize) {
+#pragma unroll
       for (uint32_t k = 0; k < VecSize; k++) {
         float x_fp32 = static_cast<float>(x[i][j + k]);
-        float x_scaled = x_fp32 * col_scale[threadIdx.x + (j + k) * 32];
+        float x_scaled = x_fp32 * scales[threadIdx.x + (j + k) * 32];
         shm[threadIdx.x * VecSize + j * 32 + k][i * 16 + threadIdx.y] =
             static_cast<OutT>(x_scaled);
       }
@@ -204,10 +232,11 @@ template <typename T, typename Context>
 void FusedTransposeSplitQuantKernel(
     const Context& dev_ctx,
     const DenseTensor& x,
+    const paddle::optional<DenseTensor>& input_scales,
     const std::vector<int64_t>& tokens_per_expert,
     bool pow_2_scales,
     std::vector<DenseTensor*> outs,
-    std::vector<DenseTensor*> scales) {
+    std::vector<DenseTensor*> output_scales) {
   auto x_dims = x.dims();
   const int64_t M = x_dims[0];
   const int64_t K = x_dims[1];
@@ -221,8 +250,8 @@ void FusedTransposeSplitQuantKernel(
     if (outs[i] != nullptr) {
       dev_ctx.template Alloc<phi::dtype::float8_e4m3fn>(outs[i]);
     }
-    if (scales[i] != nullptr) {
-      dev_ctx.template Alloc<float>(scales[i]);
+    if (output_scales[i] != nullptr) {
+      dev_ctx.template Alloc<float>(output_scales[i]);
     }
   }
 
@@ -245,8 +274,8 @@ void FusedTransposeSplitQuantKernel(
 
   for (size_t i = 0; i < num_experts; i++) {
     meta_ptr[num_experts * 2 + i] =
-        scales[i] != nullptr
-            ? reinterpret_cast<int64_t>(scales[i]->data<float>())
+        output_scales[i] != nullptr
+            ? reinterpret_cast<int64_t>(output_scales[i]->data<float>())
             : 0;
   }
 
@@ -255,23 +284,35 @@ void FusedTransposeSplitQuantKernel(
 
   auto stream = dev_ctx.stream();
 
-  dim3 grid(M / 128, (K + 127) / 128);
+  // pre-compute on CPU to reduce size_t division cost in kernel
+  const size_t k_scaled = (K + 127) / 128;
+  dim3 grid(M / 128, k_scaled);
   dim3 block(32, 16);
 
-#define LAUNCH_KERNEL(POW_2_SCALES, VEC_SIZE)                      \
-  FusedTransposeSplitQuantKernel<phi::dtype::float8_e4m3fn,        \
-                                 POW_2_SCALES,                     \
-                                 VEC_SIZE>                         \
-      <<<grid, block, 0, stream>>>(x.data<phi::dtype::bfloat16>(), \
-                                   meta_gpu.data<int64_t>(),       \
-                                   num_experts,                    \
-                                   K);
+#define DTYPE_CASE(dtype, type) dtype == phi::DataType::type
+#define LAUNCH_KERNEL(T, POW_2_SCALES, VEC_SIZE)                        \
+  FusedTransposeSplitQuantKernel<T,                                     \
+                                 phi::dtype::float8_e4m3fn,             \
+                                 POW_2_SCALES,                          \
+                                 VEC_SIZE><<<grid, block, 0, stream>>>( \
+      x.data<T>(),                                                      \
+      input_scales ? input_scales.get_ptr()->data<float>() : nullptr,   \
+      meta_gpu.data<int64_t>(),                                         \
+      num_experts,                                                      \
+      K,                                                                \
+      k_scaled);
+#define DISPATCH_DATATYPE(POW_2_SCALES, VEC_SIZE)              \
+  if (DTYPE_CASE(x.dtype(), BFLOAT16)) {                       \
+    LAUNCH_KERNEL(phi::bfloat16, POW_2_SCALES, VEC_SIZE);      \
+  } else if (DTYPE_CASE(x.dtype(), FLOAT8_E4M3FN)) {           \
+    LAUNCH_KERNEL(phi::float8_e4m3fn, POW_2_SCALES, VEC_SIZE); \
+  }
 
 #define LAUNCH_KERNEL_PARTIAL(VEC_SIZE) \
   if (pow_2_scales) {                   \
-    LAUNCH_KERNEL(true, VEC_SIZE);      \
+    DISPATCH_DATATYPE(true, VEC_SIZE);  \
   } else {                              \
-    LAUNCH_KERNEL(false, VEC_SIZE);     \
+    DISPATCH_DATATYPE(false, VEC_SIZE); \
   }
 
   if (K % 4 == 0) {
@@ -296,7 +337,8 @@ PD_REGISTER_KERNEL(fused_transpose_split_quant,
                    double,
                    int,
                    int64_t,
-                   phi::dtype::bfloat16) {
+                   phi::dtype::bfloat16,
+                   phi::dtype::float8_e4m3fn) {
   kernel->OutputAt(0).SetDataType(phi::DataType::FLOAT8_E4M3FN);
   kernel->OutputAt(1).SetDataType(phi::DataType::FLOAT32);
 }
diff --git a/paddle/phi/ops/yaml/fused_ops.yaml b/paddle/phi/ops/yaml/fused_ops.yaml
@@ -916,12 +916,13 @@
   support_dygraph_mode : true
 
 - op: fused_transpose_split_quant
-  args: (Tensor x, IntArray tokens_per_expert, bool pow_2_scales=false)
+  args: (Tensor x, Tensor input_scales, IntArray tokens_per_expert, bool pow_2_scales=false)
   output: Tensor[](out){tokens_per_expert.size()}, Tensor[](scales){tokens_per_expert.size()}
   infer_meta:
       func: FusedTransposeSplitQuantInferMeta
   kernel:
       func: fused_transpose_split_quant
+  optional: input_scales
   support_dygraph_mode : true
 
 - op: fused_weighted_swiglu_act_quant
diff --git a/python/paddle/incubate/nn/functional/fp8.py b/python/paddle/incubate/nn/functional/fp8.py
@@ -173,7 +173,9 @@ def fused_swiglu_weighted_bwd(
         return _C_ops.fused_swiglu_weighted_bwd(o1, do2_s, unzipped_probs)
 
 
-def fused_transpose_split_quant(x, tokens_per_expert, pow_2_scales=False):
+def fused_transpose_split_quant(
+    x, input_scales, tokens_per_expert, pow_2_scales=False
+):
     """
     Applies fused transpose, split, and quantization operation for Mixture of Experts (MoE) models.
 
@@ -215,7 +217,7 @@ def fused_transpose_split_quant(x, tokens_per_expert, pow_2_scales=False):
             >>> x = paddle.randn([384, 512], dtype='bfloat16')
             >>> x = paddle.clip(x, min=-50, max=50)
             >>> tokens_per_expert = [128, 128, 128]
-            >>> outs, scales = F.fused_transpose_split_quant(x, tokens_per_expert, pow_2_scales=True)
+            >>> outs, scales = F.fused_transpose_split_quant(x,None, tokens_per_expert, pow_2_scales=True)
             >>> print(outs[0].shape)
             [512, 128]
             >>> print(scales[0].shape)
@@ -228,7 +230,7 @@ def fused_transpose_split_quant(x, tokens_per_expert, pow_2_scales=False):
 
     if in_dynamic_or_pir_mode():
         return _C_ops.fused_transpose_split_quant(
-            x, tokens_per_expert, pow_2_scales
+            x, input_scales, tokens_per_expert, pow_2_scales
         )
 
 
diff --git a/test/legacy_test/test_fused_transpose_split_quant_op.py b/test/legacy_test/test_fused_transpose_split_quant_op.py
