From 28ca2e5ffa78298883bfcb900c937dc1dc72e4a0 Mon Sep 17 00:00:00 2001
From: wangchaochaohu <wangchao66@baidu.com>
Date: Tue, 29 Oct 2019 14:56:13 +0800
Subject: [PATCH] strided_slice perforamnce improvement test=develop (#20852)

---
 paddle/fluid/operators/strided_slice_op.h | 60 ++++++++++++++++-------
 1 file changed, 41 insertions(+), 19 deletions(-)

diff --git a/paddle/fluid/operators/strided_slice_op.h b/paddle/fluid/operators/strided_slice_op.h
index 5baacc7ea1..9f7ade5ec4 100644
--- a/paddle/fluid/operators/strided_slice_op.h
+++ b/paddle/fluid/operators/strided_slice_op.h
@@ -241,8 +241,6 @@ class StridedSliceKernel : public framework::OpKernel<T> {
       reverse_axis[axis_index] = (reverse_vector[axis] == 1) ? true : false;
     }
 
-    framework::Tensor tmp;
-
     auto out_dims_origin = out_dims;
     if (decrease_axis.size() > 0) {
       std::vector<int> new_out_shape;
@@ -263,21 +261,34 @@ class StridedSliceKernel : public framework::OpKernel<T> {
       out_dims_origin = framework::make_ddim(new_out_shape);
     }
 
-    tmp.mutable_data<T>(out_dims, context.GetPlace());
+    bool need_reverse = false;
+    for (size_t axis = 0; axis < axes.size(); axis++) {
+      if (reverse_vector[axis] == 1) {
+        need_reverse = true;
+        break;
+      }
+    }
+
     out->Resize(out_dims);
     out->mutable_data<T>(context.GetPlace());
     auto in_t =
         framework::EigenTensor<T, D, Eigen::RowMajor, Eigen::DenseIndex>::From(
             *in);
-    auto tmp_t =
-        framework::EigenTensor<T, D, Eigen::RowMajor, Eigen::DenseIndex>::From(
-            tmp);
     auto out_t =
         framework::EigenTensor<T, D, Eigen::RowMajor, Eigen::DenseIndex>::From(
             *out, out_dims);
-    tmp_t.device(place) =
-        in_t.stridedSlice(starts_indices, ends_indices, strides_indices);
-    out_t.device(place) = tmp_t.reverse(reverse_axis);
+    if (need_reverse) {
+      framework::Tensor tmp;
+      tmp.mutable_data<T>(out_dims, context.GetPlace());
+      auto tmp_t = framework::EigenTensor<T, D, Eigen::RowMajor,
+                                          Eigen::DenseIndex>::From(tmp);
+      tmp_t.device(place) =
+          in_t.stridedSlice(starts_indices, ends_indices, strides_indices);
+      out_t.device(place) = tmp_t.reverse(reverse_axis);
+    } else {
+      out_t.device(place) =
+          in_t.stridedSlice(starts_indices, ends_indices, strides_indices);
+    }
 
     if (decrease_axis.size() > 0) {
       out->Resize(out_dims_origin);
@@ -388,22 +399,33 @@ class StridedSliceGradKernel : public framework::OpKernel<T> {
       reverse_axis[axis_index] = (reverse_vector[axis] == 1) ? true : false;
     }
 
-    framework::Tensor reverse_input;
-    reverse_input.mutable_data<T>(in_dims, context.GetPlace());
-
+    bool need_reverse = false;
+    for (size_t axis = 0; axis < axes.size(); axis++) {
+      if (reverse_vector[axis] == 1) {
+        need_reverse = true;
+        break;
+      }
+    }
     auto in_t =
         framework::EigenTensor<T, D, Eigen::RowMajor, Eigen::DenseIndex>::From(
             *d_input);
-    auto reverse_in_t =
-        framework::EigenTensor<T, D, Eigen::RowMajor, Eigen::DenseIndex>::From(
-            reverse_input);
     auto out_t =
         framework::EigenTensor<T, D, Eigen::RowMajor, Eigen::DenseIndex>::From(
             *d_out, out_dims);
-
-    reverse_in_t.device(place) = in_t.reverse(reverse_axis);
-    out_t.stridedSlice(starts_indices, ends_indices, strides_indices)
-        .device(place) = reverse_in_t;
+    if (need_reverse) {
+      framework::Tensor reverse_input;
+      reverse_input.mutable_data<T>(in_dims, context.GetPlace());
+      auto reverse_in_t =
+          framework::EigenTensor<T, D, Eigen::RowMajor,
+                                 Eigen::DenseIndex>::From(reverse_input);
+
+      reverse_in_t.device(place) = in_t.reverse(reverse_axis);
+      out_t.stridedSlice(starts_indices, ends_indices, strides_indices)
+          .device(place) = reverse_in_t;
+    } else {
+      out_t.stridedSlice(starts_indices, ends_indices, strides_indices)
+          .device(place) = in_t;
+    }
   }
 };
 }  // namespace operators
-- 
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