If I add following codes in PrepareData between line 1025 and 1026
Paddle/paddle/fluid/framework/operator.cc

Lines 1025 to 1026 in 5e5e7b3

| | Scope* new_scope = nullptr; |
| | if (!need_prepare_data_) return new_scope; |

if (type_ == "gather")
   need_prepare_data_ = true;

This problem is fixed.
@sneaxiy Is this problem related to DECLARE_NO_NEED_BUFFER_VARS_INFERENCE ?

Paddle/paddle/fluid/operators/gather_op.cc

Line 119 in 5e5e7b3

| | DECLARE_NO_NEED_BUFFER_VARS_INFERENCE(GatherGradNoNeedBufferVarInference, "X"); |