From b79bf021761d21099bcedf2ca68edcf7ff561dbb Mon Sep 17 00:00:00 2001
From: Liu Yiqun <liuyiqun01@baidu.com>
Date: Thu, 26 Dec 2019 06:09:54 +0000
Subject: [PATCH] Optimize the InferShape of reduce_sum.

---
 lite/operators/reduce_ops.cc | 32 +++++++++++++++++---------------
 1 file changed, 17 insertions(+), 15 deletions(-)

diff --git a/lite/operators/reduce_ops.cc b/lite/operators/reduce_ops.cc
index e986b0ca54..0aada7293e 100644
--- a/lite/operators/reduce_ops.cc
+++ b/lite/operators/reduce_ops.cc
@@ -29,39 +29,41 @@ bool ReduceOp::CheckShape() const {
 }
 
 bool ReduceOp::InferShape() const {
-  auto x_dims = param_.x->dims();
+  auto& x_dims = param_.x->dims();
   auto x_rank = x_dims.size();
-  auto dims = param_.dim;
+  auto& dims = param_.dim;
   for (size_t i = 0; i < dims.size(); ++i) {
     if (dims[i] < 0) dims[i] = x_rank + dims[i];
     CHECK_LT(dims[i], x_rank)
         << "The dim should be in the range [-rank(input), rank(input).";
   }
-  sort(dims.begin(), dims.end());
   bool reduce_all = param_.reduce_all;
   bool keep_dim = param_.keep_dim;
 
   if (reduce_all) {
     if (keep_dim)
-      param_.output->Resize(lite::DDim(std::vector<int64_t>(x_rank, 1)));
+      param_.output->Resize(std::vector<int64_t>(x_rank, 1));
     else
-      param_.output->Resize(lite::DDim(std::vector<int64_t>{1}));
+      param_.output->Resize(std::vector<int64_t>{1});
   } else {
-    auto dims_vector = x_dims.Vectorize();
+    size_t out_rank = keep_dim ? x_rank : x_rank - dims.size();
+    DDim out_dims(out_rank);
     if (keep_dim) {
       for (size_t i = 0; i < dims.size(); ++i) {
-        dims_vector[dims[i]] = 1;
+        out_dims[dims[i]] = 1;
       }
     } else {
-      const int kDelFlag = -2;
-      for (size_t i = 0; i < dims.size(); ++i) {
-        dims_vector[dims[i]] = kDelFlag;
+      sort(dims.begin(), dims.end());
+      int dim_index = 0;
+      int out_index = 0;
+      for (size_t i = 0; i < x_rank; ++i) {
+        if (dims[dim_index] == i) {
+          dim_index++;
+        } else {
+          out_dims[out_index++] = x_dims[i];
+        }
       }
-      dims_vector.erase(
-          remove(dims_vector.begin(), dims_vector.end(), kDelFlag),
-          dims_vector.end());
     }
-    auto out_dims = lite::DDim(dims_vector);
     param_.output->Resize(out_dims);
     if (dims[0] != 0) {
       param_.output->set_lod(param_.x->lod());
@@ -70,7 +72,7 @@ bool ReduceOp::InferShape() const {
   return true;
 }
 
-bool ReduceOp::AttachImpl(const cpp::OpDesc &opdesc, lite::Scope *scope) {
+bool ReduceOp::AttachImpl(const cpp::OpDesc& opdesc, lite::Scope* scope) {
   param_.x =
       scope->FindVar(opdesc.Input("X").front())->GetMutable<lite::Tensor>();
   param_.output =
-- 
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