refine WhileGradOp code

Author: JiayiFeng

paddle/operators/while_op.cc

@@ -219,18 +219,15 @@ class WhileGradOpDescMaker : public framework::SingleGradOpDescMaker {
 
     auto *grad_block = this->grad_block_[0];
     auto *fwd_block = grad_block->ParentBlock();
-    // auto *parent_block = fwd_block->ParentBlock();
 
     // Not all of IGs will be generated by inner gradient operators of while op.
     // Ignore IGs that is not generated by the inside block.
     std::unordered_set<std::string> inner_op_outputs;
-    LOG(INFO) << "FUCK1";
     for (const auto *op : grad_block->AllOps()) {
       for (auto &oname : op->OutputArgumentNames()) {
         inner_op_outputs.insert(oname);
       }
     }
-    LOG(INFO) << "FUCK2";
     auto igs = InputGrad(kX, /*do not drop empty gradient*/ false);
     for (auto &each_ig : igs) {
       if (inner_op_outputs.find(each_ig) == inner_op_outputs.end()) {
@@ -243,11 +240,13 @@ class WhileGradOpDescMaker : public framework::SingleGradOpDescMaker {
     // OG should be re-calculated by step blocks, since many outputs of while op
     // do not need to calculate gradients.
     std::unordered_set<std::string> block_ins;
-    std::copy(Input(kX).begin(), Input(kX).end(),
-              std::inserter(block_ins, block_ins.end()));
-    std::copy(Output(kOutputs).begin(), Output(kOutputs).end(),
-              std::inserter(block_ins, block_ins.end()));
-
+    block_ins.reserve(Input(kX).size() + Output(kOutputs).size());
+    for (auto &p : Input(kX)) {
+      block_ins.insert(p);
+    }
+    for (auto &o : Output(kOutputs)) {
+      block_ins.insert(o);
+    }
     std::unordered_set<std::string> extra_inputs;
     for (const auto *op : grad_block->AllOps()) {
       for (auto &input_name : op->InputArgumentNames()) {
@@ -257,15 +256,6 @@ class WhileGradOpDescMaker : public framework::SingleGradOpDescMaker {
             fwd_block->FindVar(input_name) != nullptr) {
           continue;
         }
-
-        /*
-        if (parent_block->FindVarRecursive(input_name) == nullptr) {
-          VLOG(5) << "WARNING! Variable '" << input_name
-                  << "' is the input of '" << op->Type()
-                  << "'. But can not be found in any block.";
-          continue;
-        }
-        */
         extra_inputs.insert(input_name);
       }
       for (auto &output_name : op->OutputArgumentNames()) {