openmp parallel seems to not work for the sample code DNN

I compiled and ran the sample code for SampleDNNL. However, it appears that parallelism using multiple threads is not working, even though the OpenMP library has been successfully compiled. I would like to understand why this is happening.

Start by reproducing the reported behavior with the SampleDNNL sample after compiling the OpenMP library, then inspect how the sample is built and launched. Compare single-threaded and multi-threaded runs and document whether the issue is in the sample or its OpenMP configuration; done means identifying the cause and confirming parallel execution works or the limitation is clearly explained.

Written by the indexing model from the issue text.