Speedup roi_perspective_transform op by caching the information of linear interpolation in forward

paddle/fluid/operators/detection/roi_perspective_transform_op.cc

@@ -494,6 +494,8 @@ class ROIPerspectiveTransformOp : public framework::OperatorWithKernel {
     auto out_dims = framework::make_ddim(out_dims_v);
 
     ctx->SetOutputDim("Out", out_dims);
+    ctx->SetOutputDim("Out2InIdx", out_dims);
+    ctx->SetOutputDim("Out2InWeights", out_dims);
     ctx->ShareLoD("ROIs", /*->*/ "Out");
   }
 
@@ -550,6 +552,20 @@ class ROIPerspectiveTransformOpMaker
         "(Tensor), "
         "The output of ROIPerspectiveTransformOp is a 4-D tensor with shape "
         "(num_rois, channels, transformed_h, transformed_w).");
+    AddOutput("Out2InIdx",
+              "(Tensor), "
+              "An intermediate tensor used to map indexes of input feature map "
+              "and indexes of output feature map."
+              "The shape of the tensor is [out_size, 4] and out_size is the "
+              "number of elements in output feature map.")
+        .AsIntermediate();
+    AddOutput("Out2InWeights",
+              "(Tensor), "
+              "An intermediate tensor used to record the weights of bilinear "
+              "interpolatein for each element in output. The shape of the "
+              "tensor is [out_size, 4] and out_size is the number of elements "
+              "in output feature map.")
+        .AsIntermediate();
     AddAttr<float>("spatial_scale",
                    "(float, default 1.0), "
                    "Spatial scale factor to scale ROI coords.")
@@ -580,6 +596,8 @@ class ROIPerspectiveTransformGradDescMaker
     op->SetType("roi_perspective_transform_grad");
     op->SetInput("X", Input("X"));
     op->SetInput("ROIs", Input("ROIs"));
+    op->SetInput("Out2InIdx", Output("Out2InIdx"));
+    op->SetInput("Out2InWeights", Output("Out2InWeights"));
     op->SetInput(framework::GradVarName("Out"), OutputGrad("Out"));
     op->SetOutput(framework::GradVarName("X"), InputGrad("X"));
     op->SetAttrMap(Attrs());

paddle/fluid/operators/detection/roi_perspective_transform_op.cu

@@ -14,6 +14,7 @@ limitations under the License. */
 
 #include <algorithm>
 #include "paddle/fluid/framework/op_registry.h"
+#include "paddle/fluid/operators/math/math_function.h"
 #include "paddle/fluid/platform/cuda_primitives.h"
 #include "paddle/fluid/platform/float16.h"
 
@@ -115,8 +116,9 @@ __device__ bool in_quad(T x, T y, T roi_x[], T roi_y[]) {
 template <typename T>
 __device__ void bilinear_interpolate(const T* in_data, const int channels,
                                      const int width, const int height,
-                                     int in_n, int in_c, T in_w, T in_h,
-                                     T* val) {
+                                     int in_n, int in_c, T in_w, T in_h, T* val,
+                                     int out_idx, int* out2in_idx,
+                                     T* out2in_w) {
   // Deal with cases that source coords are out of feature map boundary
   if (GT<T>(-0.5, in_w) || GT<T>(in_w, width - 0.5) || GT<T>(-0.5, in_h) ||
       GT<T>(in_h, height - 0.5)) {
@@ -165,6 +167,16 @@ __device__ void bilinear_interpolate(const T* in_data, const int channels,
   T w3 = w_floor * h_floor;
   T w4 = w_floor * h_ceil;
   val[0] = w1 * v1 + w2 * v2 + w3 * v3 + w4 * v4;
+
+  int base_idx = (in_n * channels + in_c) * height * width;
+  out2in_idx[out_idx * 4] = base_idx + in_h_floor * width + in_w_floor;
+  out2in_idx[out_idx * 4 + 1] = base_idx + in_h_ceil * width + in_w_floor;
+  out2in_idx[out_idx * 4 + 2] = base_idx + in_h_ceil * width + in_w_ceil;
+  out2in_idx[out_idx * 4 + 3] = base_idx + in_h_floor * width + in_w_ceil;
+  out2in_w[out_idx * 4] = w1;
+  out2in_w[out_idx * 4 + 1] = w2;
+  out2in_w[out_idx * 4 + 2] = w3;
+  out2in_w[out_idx * 4 + 3] = w4;
 }
 
 /**
@@ -262,13 +274,11 @@ __device__ void get_transform_matrix(const int transformed_width,
 }
 
 template <typename T>
-__global__ void RoiTransformKernel(const float* input_data,
-                                   const float* rois_data,
-                                   const int* roi2image_data, int num_rois,
-                                   int in_height, int in_width, int channels,
-                                   int transformed_height,
-                                   int transformed_width, float spatial_scale,
-                                   T* output_data) {
+__global__ void RoiTransformKernel(
+    const float* input_data, const float* rois_data, const int* roi2image_data,
+    int num_rois, int in_height, int in_width, int channels,
+    int transformed_height, int transformed_width, float spatial_scale,
+    T* output_data, int* out2in_idx, T* out2in_w) {
   int output_size =
       num_rois * transformed_height * transformed_width * channels;
 
@@ -311,7 +321,8 @@ __global__ void RoiTransformKernel(const float* input_data,
         // Perform bilinear interpolation
         int in_n = roi2image_data[n];
         bilinear_interpolate<T>(input_data, channels, in_width, in_height, in_n,
-                                c, in_w, in_h, output_data + index);
+                                c, in_w, in_h, output_data + index, index,
+                                out2in_idx, out2in_w);
       }
 
     } else {
@@ -328,6 +339,16 @@ class CUDAROIPerspectiveTransformOpKernel : public framework::OpKernel<T> {
     auto* in = ctx.Input<framework::Tensor>("X");
     auto* rois = ctx.Input<framework::LoDTensor>("ROIs");
     auto* out = ctx.Output<framework::Tensor>("Out");
+    auto* out2in_idx = ctx.Output<framework::Tensor>("Out2InIdx");
+    auto* out2in_w = ctx.Output<framework::Tensor>("Out2InWeights");
+
+    int* out2in_idx_data =
+        out2in_idx->mutable_data<int>({out->numel(), 4}, ctx.GetPlace());
+    T* out2in_w_data =
+        out2in_w->mutable_data<T>({out->numel(), 4}, ctx.GetPlace());
+
+    math::SetConstant<platform::CUDADeviceContext, int> init;
+    init(ctx.cuda_device_context(), out2in_idx, static_cast<int>(-1));
 
     auto transformed_height = ctx.Attr<int>("transformed_height");
     auto transformed_width = ctx.Attr<int>("transformed_width");
@@ -364,7 +385,7 @@ class CUDAROIPerspectiveTransformOpKernel : public framework::OpKernel<T> {
     RoiTransformKernel<T><<<grid, block, 0, stream>>>(
         input_data, rois_data, roi2image_dev.data<int>(), rois_num, in_height,
         in_width, channels, transformed_height, transformed_width,
-        spatial_scale, output_data);
+        spatial_scale, output_data, out2in_idx_data, out2in_w_data);
   }
 };
 
@@ -420,100 +441,42 @@ __device__ T get_feature_gradient(T xs, T ys, int w, int h, const int width,
 }
 
 template <typename T>
-__global__ void RoiTransformGradKernel(
-    const size_t* lod, const T* rois_data, int batch_size, int num_rois,
-    int in_height, int in_width, int channels, int transformed_height,
-    int transformed_width, float spatial_scale, const T* out_grad_data,
-    T* in_grad_data) {
-  int input_size = batch_size * in_height * in_width * channels;
-
-  CUDA_1D_KERNEL_LOOP(index, input_size) {
-    // (n, c, h, w) coords in input
-    int in_w = idx4_4(index, batch_size, channels, in_height, in_width);
-    int in_h = idx4_3(index, batch_size, channels, in_height, in_width);
-    int c = idx4_2(index, batch_size, channels, in_height, in_width);
-    int n = idx4_1(index, batch_size, channels, in_height, in_width);
-
-    T gradient = 0.0;
-    // Accumulate gradient over all RoIs that interpolated this element
-    for (size_t roi_idx = lod[n]; roi_idx < lod[n + 1]; ++roi_idx) {
-      const T* rois = rois_data + roi_idx * 8;
-      T roi_x[4];
-      T roi_y[4];
-      for (int k = 0; k < 4; ++k) {
-        roi_x[k] = rois[2 * k] * spatial_scale;
-        roi_y[k] = rois[2 * k + 1] * spatial_scale;
-      }
-
-      // Get transform matrix
-      T matrix[9];
-      get_transform_matrix<T>(transformed_width, transformed_height, roi_x,
-                              roi_y, matrix);
-
-      const T* out_grad_ptr =
-          out_grad_data +
-          (roi_idx * channels + c) * transformed_height * transformed_width;
-      for (int out_h = 0; out_h < transformed_height; ++out_h) {
-        for (int out_w = 0; out_w < transformed_width; ++out_w) {
-          T src_w;
-          T src_h;
-          get_source_coords<T>(matrix, out_w, out_h, &src_w, &src_h);
-          if (in_quad<T>(src_w, src_h, roi_x, roi_y)) {
-            if (GT<T>(-0.5, src_w) ||
-                GT<T>(src_w, static_cast<T>(in_width - 0.5)) ||
-                GT<T>(-0.5, src_h) ||
-                GT<T>(src_h, static_cast<T>(in_height - 0.5))) {
-              continue;
-            }
-            T weight = get_feature_gradient<T>(src_w, src_h, in_w, in_h,
-                                               in_width, in_height);
-            gradient +=
-                out_grad_ptr[out_h * transformed_width + out_w] * weight;
-          }
-        }
-      }
+__global__ void RoiTransformGradKernel(int out_size, const int* out2in_idx_data,
+                                       const T* out2in_w_data,
+                                       const T* out_grad_data,
+                                       T* in_grad_data) {
+  CUDA_1D_KERNEL_LOOP(index, out_size * 4) {
+    int in_idx = out2in_idx_data[index];
+    if (in_idx > 0) {
+      int out_idx = index / 4;
+      atomicAdd(in_grad_data + in_idx,
+                out_grad_data[out_idx] * out2in_w_data[index]);
     }
-    in_grad_data[index] = gradient;
   }
 }
 
 template <typename T>
 class CUDAROIPerspectiveTransformGradOpKernel : public framework::OpKernel<T> {
  public:
   void Compute(const framework::ExecutionContext& ctx) const override {
-    auto* in = ctx.Input<framework::Tensor>("X");
-    auto* rois = ctx.Input<framework::LoDTensor>("ROIs");
+    auto* out2in_idx = ctx.Input<framework::LoDTensor>("Out2InIdx");
+    auto* out2in_w = ctx.Input<framework::LoDTensor>("Out2InWeights");
     auto* out_grad =
         ctx.Input<framework::Tensor>(framework::GradVarName("Out"));
     auto* in_grad = ctx.Output<framework::Tensor>(framework::GradVarName("X"));
 
-    auto transformed_height = ctx.Attr<int>("transformed_height");
-    auto transformed_width = ctx.Attr<int>("transformed_width");
-    auto spatial_scale = ctx.Attr<float>("spatial_scale");
-
-    auto in_dims = in->dims();
-    int batch_size = in_dims[0];
-    int channels = in_dims[1];
-    int in_height = in_dims[2];
-    int in_width = in_dims[3];
-    int rois_num = rois->dims()[0];
-
     T* in_grad_data = in_grad->mutable_data<T>(ctx.GetPlace());
     const T* out_grad_data = out_grad->data<T>();
-    const T* rois_data = rois->data<T>();
-
-    auto lod = rois->lod().back();
-    auto lod_data = lod.CUDAData(ctx.GetPlace());
+    const int* out2in_idx_data = out2in_idx->data<int>();
+    const T* out2in_w_data = out2in_w->data<T>();
 
-    int in_size = in->numel();
+    int out_size = out_grad->numel();
     auto stream = ctx.cuda_device_context().stream();
     int block = 512;
-    int grid = (in_size + block - 1) / block;
+    int grid = (out_size * 4 + block - 1) / block;
 
     RoiTransformGradKernel<T><<<grid, block, 0, stream>>>(
-        lod_data, rois_data, batch_size, rois_num, in_height, in_width,
-        channels, transformed_height, transformed_width, spatial_scale,
-        out_grad_data, in_grad_data);
+        out_size, out2in_idx_data, out2in_w_data, out_grad_data, in_grad_data);
   }
 };
 

python/paddle/fluid/layers/detection.py

@@ -1827,11 +1827,17 @@ def roi_perspective_transform(input,
     helper = LayerHelper('roi_perspective_transform', **locals())
     dtype = helper.input_dtype()
     out = helper.create_variable_for_type_inference(dtype)
+    out2in_idx = helper.create_variable_for_type_inference(dtype="int32")
+    out2in_w = helper.create_variable_for_type_inference(dtype)
     helper.append_op(
         type="roi_perspective_transform",
         inputs={"X": input,
                 "ROIs": rois},
-        outputs={"Out": out},
+        outputs={
+            "Out": out,
+            "Out2InIdx": out2in_idx,
+            "Out2InWeights": out2in_w
+        },
         attrs={
             "transformed_height": transformed_height,
             "transformed_width": transformed_width,

python/paddle/fluid/tests/unittests/test_roi_perspective_transform_op.py

@@ -299,6 +299,10 @@ def test_check_output(self):
         self.check_output()
 
     def test_check_grad(self):
+        self.outputs['Out2InIdx'] = np.zeros(
+            [np.product(self.outputs['Out'].shape), 4]).astype("int32")
+        self.outputs['Out2InWeights'] = np.zeros(
+            [np.product(self.outputs['Out'].shape), 4]).astype("float32")
         self.check_grad(['X'], 'Out')