add namespace and reduce warning

paddle/operators/crop_op.h

@@ -38,10 +38,10 @@ class CropKernel : public framework::OpKernel {
     auto out_stride = framework::stride(out->dims());
     auto offsets = context.Attr<std::vector<int>>("offsets");
     PADDLE_ENFORCE_EQ(
-        x->dims().size(), offsets.size(),
+        x->dims().size(), static_cast<int64_t>(offsets.size()),
         "Offsets size should be equal to dimension size of input tensor.");
     int64_t offset = 0;
-    for (int i = 0; i < offsets.size(); ++i) {
+    for (size_t i = 0; i < offsets.size(); ++i) {
       offset += (x_stride[i] * offsets[i]);
     }
     StridedMemcpy<T>(context.device_context(), x_data + offset, x_stride,
@@ -57,7 +57,7 @@ void CropGradFunction(const framework::ExecutionContext& context) {
     d_x->mutable_data<T>(context.GetPlace());
     auto offsets = context.Attr<std::vector<int>>("offsets");
     Eigen::array<std::pair<int, int>, D> paddings;
-    for (int i = 0; i < D; ++i) {
+    for (size_t i = 0; i < D; ++i) {
       paddings[i].first = offsets[i];
       paddings[i].second = d_x->dims()[i] - d_out->dims()[i] - offsets[i];
     }

paddle/operators/multiplex_op.h

@@ -37,7 +37,7 @@ class MultiplexCPUKernel : public framework::OpKernel {
     Place place = boost::get<Place>(ctx.GetPlace());
     for (auto i = 0; i < rows; i++) {
       int k = (int)index[i] + 1;
-      PADDLE_ENFORCE_LT(k, ins.size(),
+      PADDLE_ENFORCE_LT(static_cast<size_t>(k), ins.size(),
                         "index exceeds the number of candidate tensors.");
       memory::Copy(place, out->data<T>() + i * cols, place,
                    ins[k]->data<T>() + i * cols, cols * sizeof(T));
@@ -74,5 +74,5 @@ class MultiplexGradCPUKernel : public framework::OpKernel {
     }
   }
 };
-}
-}
+}  // namespace operators
+}  // namespace paddle