Evaluate the occurrence of padding in a separate function.

src/operator/nn/mkldnn/mkldnn_concat.cc

@@ -29,8 +29,15 @@
 namespace mxnet {
 namespace op {
 
-MKLDNNConcatFwd::MKLDNNConcatFwd(
-    int concat_dim, const std::vector<mkldnn::memory::desc> &data_md)
+static inline bool IsUsingPadding(const mkldnn::memory::desc &dst_md) {
+  // make sure a blocked format is used (at least one dimension is blocked)
+  bool is_blocked_format = dst_md.data.format_kind == mkldnn_blocked &&
+                           dst_md.data.format_desc.blocking.inner_nblks > 0;
+  return is_blocked_format && !std::equal(dst_md.data.dims, dst_md.data.dims + dst_md.data.ndims,
+                                          dst_md.data.padded_dims);
+}
+
+MKLDNNConcatFwd::MKLDNNConcatFwd(int concat_dim, const std::vector<mkldnn::memory::desc> &data_md)
     : fwd_pd(concat_dim, data_md, CpuEngine::Get()->get_engine()) {
   // MKL-DNN introduced padded formats since 0.15 which require more memory
   // compared to the actual size of the tensor. Currently, MKL-DNN operators
@@ -39,14 +46,10 @@ MKLDNNConcatFwd::MKLDNNConcatFwd(
 
   // When fwd_pd uses padding, impose a plain format
   const auto &dst_md = fwd_pd.dst_desc();
-  if (dst_md.data.format_kind == mkldnn_blocked &&
-      dst_md.data.format_desc.blocking.inner_nblks > 0 &&
-      !std::equal(dst_md.data.dims, dst_md.data.dims + dst_md.data.ndims,
-                  dst_md.data.padded_dims)) {
+  if (IsUsingPadding(dst_md)) {
     auto plain_dst_tag = static_cast<mkldnn::memory::format_tag>(
         GetDefaultFormat(dst_md.data.ndims));
-    auto plain_dst_md =
-        mkldnn::memory::desc(dst_md.dims(), dst_md.data_type(), plain_dst_tag);
+    auto plain_dst_md = mkldnn::memory::desc(dst_md.dims(), dst_md.data_type(), plain_dst_tag);
     fwd_pd = mkldnn::concat::primitive_desc(plain_dst_md, concat_dim, data_md,
                                             CpuEngine::Get()->get_engine());
   }