Add debug code

paddle/fluid/framework/parallel_executor.cc

@@ -365,6 +365,7 @@ struct NCCLAllReduceOpHandle : public OpHandle {
         auto &p = static_cast<VarHandle *>(in)->place_;
         in->generated_op_->Wait(dev_ctx_[p]);
       }
+      PADDLE_ENFORCE(cudaDeviceSynchronize());
 
       auto &var_name = static_cast<VarHandle *>(this->inputs_[0])->name_;
       int dtype = -1;
@@ -393,6 +394,8 @@ struct NCCLAllReduceOpHandle : public OpHandle {
             nccl_ctx.comm, nccl_ctx.stream());
       }
       platform::dynload::ncclGroupEnd();
+
+      PADDLE_ENFORCE(cudaDeviceSynchronize());
     }
   }
 };