Cleanup of '-Wsign-compare' warnnigs. (#504)

nnvm/src/top/tensor/matrix_op.cc

@@ -34,8 +34,8 @@ inline bool DotShape(const nnvm::NodeAttrs& attrs,
     << "dot shape inconsistent: " << lshape << " X " << rshape;
 
   TShape oshape(lshape.ndim() + rshape.ndim() - 2);
-  for (int i = 0; i < lshape.ndim() - 1; i++) oshape[i] = lshape[i];
-  for (int i = 1; i < rshape.ndim(); i++) oshape[i + lshape.ndim() - 2] = rshape[i];
+  for (uint32_t i = 0; i < lshape.ndim() - 1; i++) oshape[i] = lshape[i];
+  for (uint32_t i = 1; i < rshape.ndim(); i++) oshape[i + lshape.ndim() - 2] = rshape[i];
 
   NNVM_ASSIGN_OUTPUT_SHAPE(attrs, *out_attrs, 0, oshape);
   return true;

nnvm/src/top/tensor/reduce.cc

@@ -145,7 +145,7 @@ Example::
       for (dim_t i = 0; i < param.axis.ndim(); ++i) {
         exclude_axis.insert(param.axis[i]);
       }
-      for (dim_t i = 0; i < inputs[0].ndim(); ++i) {
+      for (dim_t i = 0; i < static_cast<int>(inputs[0].ndim()); ++i) {
         if (exclude_axis.count(i) == 0) {
           axis.push_back(make_const(Int(32), i));
         }

nnvm/src/top/tensor/transform.cc

@@ -760,7 +760,7 @@ inline bool TransposeCorrectLayout(const NodeAttrs& attrs,
     } else {
       CHECK_EQ(input.ndim(), param.axes.ndim());
       for (size_t i = 0; i < input.ndim(); ++i) {
-        CHECK(param.axes[i] < input.ndim());
+        CHECK(param.axes[i] < static_cast<int>(input.ndim()));
         new_layout << input.at(param.axes[i]);
       }
     }