fix some typos

paddle/operators/sequence_slice_op.cc

@@ -90,11 +90,11 @@ class SequenceSliceOpMaker : public framework::OpProtoAndCheckerMaker {
              "a vector<int> to describe the length of every input sequence for "
              "sub sequence item.");
     AddOutput("Out",
-              "(LoDTensor), The output of SequenceSliceOp.");
+              "(LoDTensor), the output of SequenceSliceOp.");
     AddComment(R"DOC(
 Sequence slice operator
 
-The operator crop a subsequence from given sequence with given start offset and subsequence length.
+The operator crops a subsequence from given sequence with given start offset and subsequence length.
 It only supports sequence (LoD Tensor with level number is 1).
 - Case:
     X = [[a1, a2;
@@ -109,7 +109,7 @@ It only supports sequence (LoD Tensor with level number is 1).
             b1, b2]
             [e1, e2]]
     LoD(Out) = {{0, 2, 3}}; Dims(Out) = (3, 2)
-NOTE: The length of the input, offset and length should be the same. The offset start from 0.
+NOTE: The first dimension size of input, the size of offset and Length, should be equal. The offset start from 0.
     )DOC");
   }
 };

paddle/operators/sequence_slice_op.h

@@ -83,7 +83,8 @@ class SequenceSliceOpKernel : public framework::OpKernel<T> {
       PADDLE_ENFORCE_LT(
           lod[0][i] + offset_data[i] + length_data[i],
           lod[0][i + 1],
-          "The target tensor's length overflow")}
+          "The target tensor's length overflow")
+    }
 
     out->mutable_data<T>(ctx.GetPlace());
     auto out_lod = SequenceSliceLoD(*in, offset_data, length_data);
@@ -140,6 +141,7 @@ class SequenceSliceGradOpKernel : public framework::OpKernel<T> {
     auto lod = in->lod();
     auto out_lod = out_grad->lod();
 
+    if (x_grad) {
       x_grad->mutable_data<T>(ctx.GetPlace());
       math::SetConstant<Place, T> set_zero;
       set_zero(ctx.device_context(), x_grad, static_cast<T>(0));
@@ -163,6 +165,7 @@ class SequenceSliceGradOpKernel : public framework::OpKernel<T> {
                         x_grad_t.data<T>());
       }
     }
+  }
 };
 
 }  // namespace operators