fix some comments

Author: wanghaox

paddle/operators/sequence_slice_op.cc

@@ -35,11 +35,14 @@ class SequenceSliceOp : public framework::OperatorWithKernel {
     auto offset_dim = ctx->GetInputDim("Offset");
     auto length_dim = ctx->GetInputDim("Length");
 
-    PADDLE_ENFORCE_EQ(offset_dim.size(), 2UL,
-                      "Only support one level sequence now.");
-    PADDLE_ENFORCE_EQ(length_dim.size(), 2UL,
-                      "Only support one level sequence now.");
-
+    PADDLE_ENFORCE_EQ(
+        offset_dim.size(), 2UL,
+        "Only support one level sequence now, The rank of offset must be 2.");
+    PADDLE_ENFORCE_EQ(
+        length_dim.size(), 2UL,
+        "Only support one level sequence now, The rank of Length must be 2.");
+
+    // Initialize the output's dims to maximum
     ctx->SetOutputDim("Out", input_dims);
     }
 

paddle/operators/sequence_slice_op.h

@@ -54,10 +54,10 @@ class SequenceSliceOpKernel : public framework::OpKernel<T> {
     PADDLE_ENFORCE_EQ(lod.size(), 1UL,
                       "Only support one level sequence now.");
     PADDLE_ENFORCE_EQ(
-        n, length->dims()[0],
+        n, static_cast<size_t>(length->dims()[0]),
         "The size of input-sequence and length-array should be the same")
     PADDLE_ENFORCE_EQ(
-        n, offset->dims()[0],
+        n, static_cast<size_t>(offset->dims()[0]),
         "The size of input-sequence and offset-array should be the same")
 
     const int64_t* offset_data = offset->data<int64_t>();