Made tensor copies a little more efficient.

dlib/dnn/tensor.h

@@ -292,15 +292,13 @@ namespace dlib
 
         resizable_tensor(const resizable_tensor& item) : _annotation(item.annotation()) 
         {
-            // TODO, do the copy with cuda?
             copy_size(item);
-            std::memcpy(data_instance.host(), item.host(), data_instance.size()*sizeof(float));
+            memcpy(data_instance, item.data_instance);
         }
         resizable_tensor(const tensor& item) : _annotation(item.annotation()) 
         {
-            // TODO, do the copy with cuda?
             copy_size(item);
-            std::memcpy(data_instance.host(), item.host(), data_instance.size()*sizeof(float));
+            memcpy(*this, item);
         }
 
         resizable_tensor(resizable_tensor&& item) { swap(item); }