Pardiso solver no threaded speedup

[Dave17]

We find that linking the threaded MKL Pardiso solver provides no performance boost - or even slows down if many threads are specified via OPNOMP_NUM_THREADS.

The Pardiso diagnostic messages report multiple threads are being used.  But the execution time slows.

Is this to be expected?

[Gennady_F_Intel]

First of all try to play with MKL_NUM_THREADS environment variables.

Then enable verbose mode ( setting msglvl == 1 ) and see the perf results for each of phases ( reordering, factorization, solving) and see the scalability results if any or any performance bottleneck

--Gennady