fix multi gpu dist train

paddle/fluid/framework/details/multi_devices_graph_builder.cc

@@ -77,6 +77,33 @@ void MultiDevSSAGraphBuilder::CreateOpHandleIOs(SSAGraph *result,
   }
 }
 
+bool MultiDevSSAGraphBuilder::IsDistTrainOp(const OpDesc &op,
+                                            OpDesc *send_op) const {
+  if (send_op == nullptr) {
+    return false;
+  }
+
+  auto checker = [&](const std::vector<std::string> opvars,
+                     const std::vector<std::string> sendvars) -> bool {
+    bool is_dist_train_op = false;
+    for (auto &var : opvars) {
+      if (var.find(".block") != std::string::npos &&
+          std::find(sendvars.begin(), sendvars.end(), var) != sendvars.end()) {
+        is_dist_train_op = true;
+        break;
+      }
+    }
+    return is_dist_train_op;
+  };
+
+  if (op.Type() == "split") {
+    return checker(op.OutputArgumentNames(), send_op->InputArgumentNames());
+  } else if (op.Type() == "concat") {
+    return checker(op.InputArgumentNames(), send_op->OutputArgumentNames());
+  }
+  return false;
+}
+
 std::unique_ptr<SSAGraph> MultiDevSSAGraphBuilder::Build(
     const ProgramDesc &program) const {
   auto graph = new SSAGraph();
@@ -88,17 +115,28 @@ std::unique_ptr<SSAGraph> MultiDevSSAGraphBuilder::Build(
       std::unordered_map<std::string, std::vector<std::unique_ptr<VarHandle>>>>(
       places_.size());
 
+  // Find "send" op first for split is in front of send.
+  OpDesc *send_op = nullptr;
+  for (auto *op : program.Block(0).AllOps()) {
+    if (op->Type() == "send") {
+      send_op = op;
+      break;
+    }
+  }
+
   bool is_forwarding = true;
   for (auto *op : program.Block(0).AllOps()) {
     if (op->Type() == "send") {
       // append send op if program is distributed trainer main program.
       // always use the first device
       CreateSendOp(&result, *op);
+    } else if (IsDistTrainOp(*op, send_op)) {
+      CreateComputationalOps(&result, *op, 1);
     } else if (IsScaleLossOp(*op)) {
       CreateScaleLossGradOp(&result);
       is_forwarding = false;
     } else {
-      CreateComputationalOps(&result, *op);
+      CreateComputationalOps(&result, *op, places_.size());
       if (!is_forwarding) {
         // Currently, we assume that once gradient is generated, it can be
         // broadcast, and each gradient is only broadcast once. But there are no
@@ -196,8 +234,9 @@ void MultiDevSSAGraphBuilder::CreateScaleLossGradOp(SSAGraph *result) const {
 }
 
 void MultiDevSSAGraphBuilder::CreateComputationalOps(SSAGraph *result,
-                                                     const OpDesc &op) const {
-  for (size_t scope_idx = 0; scope_idx < places_.size(); ++scope_idx) {
+                                                     const OpDesc &op,
+                                                     size_t num_places) const {
+  for (size_t scope_idx = 0; scope_idx < num_places; ++scope_idx) {
     auto p = places_[scope_idx];
     auto s = local_scopes_[scope_idx];
     result->ops_.emplace_back(new ComputationOpHandle(op, s, p));

paddle/fluid/framework/details/multi_devices_graph_builder.h

@@ -62,7 +62,10 @@ class MultiDevSSAGraphBuilder : public SSAGraphBuilder {
 
   void CreateSendOp(SSAGraph *result, const OpDesc &op) const;
 
-  void CreateComputationalOps(SSAGraph *result, const OpDesc &op) const;
+  bool IsDistTrainOp(const OpDesc &op, OpDesc *send_op) const;
+
+  void CreateComputationalOps(SSAGraph *result, const OpDesc &op,
+                              size_t num_places) const;
 
   void CreateScaleLossGradOp(SSAGraph *result) const;