Intel(r) MKL-DNN - when should I destroy primitive_desc?

Hi, 

Thank you for the open-source MKL-DNN product.

The documentation says little about cleaning up objects created with mkldnn_*_create functions, particularly mkldnn_primitive_desc_t objects. The simple_net.c example makes no calls to mkldnn_primitive_desc_destroy function, and valgrind indeed shows leaked pd objects.

Thanks,
Dima