make lodtensor_printer usable in gpu setting

test=develop

paddle/fluid/platform/lodtensor_printer.cc

@@ -52,16 +52,26 @@ void PrintVar(framework::Scope* scope, const std::string& var_name,
     return;
   }
 
+  framework::LoDTensor printed_tensor;
+  printed_tensor.set_lod(tensor->lod());
+  printed_tensor.Resize(tensor->dims());
+  if (platform::is_cpu_place(tensor->place())) {
+    printed_tensor.ShareDataWith(*tensor);
+  } else {
+    platform::CPUPlace place;
+    framework::TensorCopy(*tensor, place, &printed_tensor);
+  }
+
 #define PrintLoDTensorCallback(cpp_type, proto_type)                    \
   do {                                                                  \
     if (tensor->type() == proto_type) {                                 \
-      print_lod_tensor<cpp_type>(var_name, *tensor, print_info); \
+      print_lod_tensor<cpp_type>(var_name, printed_tensor, print_info); \
       return;                                                           \
     }                                                                   \
   } while (0)
 
   _ForEachDataType_(PrintLoDTensorCallback);
-  VLOG(1) << "PrintVar: unrecognized data type:" << tensor->type();
+  VLOG(1) << "PrintVar: unrecognized data type:" << printed_tensor.type();
 }
 
 }  // end namespace platform