remove unreferenced vars

paddle/framework/prune.cc

@@ -17,6 +17,7 @@ limitations under the License. */
 #include <algorithm>
 #include <set>
 #include <string>
+#include <unordered_map>
 #include <vector>
 
 #include <glog/logging.h>
@@ -103,33 +104,31 @@ void prune_impl(const proto::ProgramDesc& input, proto::ProgramDesc* output,
     }
   }
 
-  // remove the vars in ProgramDesc that are not referenced in
-  // the pruned ops
-  std::unordered_map<std::string name, proto::VarDesc> var_map;
+  // remove the VarDescs in BlockDesc that are not referenced in
+  // the pruned OpDescs
+  std::unordered_map<std::string, proto::VarDesc> var_map;
   auto* var_field = output->mutable_blocks(block_id)->mutable_vars();
-  for (auto* var : *var_field) {
-    var_map[var->name()] = *var;
-  }
-
-  //  for (size_t i = 0; i < var_field->size(); ++i) {
-  //    auto* var = (*var_field)[i];
-  //    var_map[var->name()] = *var;
-  //  }
-
-  //  var_field->Clear();
-  //  for (size_t i = 0; i < op_field->size(); ++i) {
-  //    auto* op = (*op_field)[i];
-
-  //    auto* input_field = op->mutable_inputs();
-  //    for (size_t j = 0; j < input_field->size(); ++j) {
-  //        auto* input_names = (*input_field)[j]->arguments();
-  //        for ()
-  //        *var_field->Add() = var_map[]
-  //    }
-  //    auto* ouput_field = op->mutable_outputs();
-  //    for (size_t k = 0; k < output_field->size(); ++k) {
-  //    }
-  //  }
+  for (const auto& var : *var_field) {
+    var_map[var.name()] = var;
+  }
+
+  var_field->Clear();
+  for (const auto& op : *op_field) {
+    // add VarDescs of all input arguments for each OpDesc
+    auto& input_field = op.inputs();
+    for (auto& input : input_field) {
+      for (auto& arg : input.arguments()) {
+        *var_field->Add() = var_map[arg];
+      }
+    }
+    // add VarDescs of all output arguments for each OpDesc
+    auto& output_field = op.outputs();
+    for (auto& output : output_field) {
+      for (auto& arg : output.arguments()) {
+        *var_field->Add() = var_map[arg];
+      }
+    }
+  }
 }
 
 // TODO(fengjiayi): Prune() could be inplaced to avoid unnecessary copies