Refine GRU Operator

paddle/operators/gru_op.h

@@ -154,6 +154,7 @@ class GRUGradKernel : public framework::OpKernel<T> {
     }
     if (h0_grad) {
       ordered_h0_grad.mutable_data<T>(h0_grad->dims(), context.GetPlace());
+      zero(context.device_context(), &ordered_h0_grad, static_cast<T>(0.0));
     }
 
     bool is_reverse = context.Attr<bool>("is_reverse");

python/paddle/v2/framework/tests/test_gru_op.py

@@ -149,7 +149,7 @@ class TestGRUOpReverse(TestGRUOp):
         self.is_reverse = True
         self.attrs = {
             'activation': 'tanh',
-            'gate_activation': 'tanh',
+            'gate_activation': 'sigmoid',
             'is_reverse': self.is_reverse
         }