Multi-threaded PSSYEVD not threading actually

Dear all,

When calling the SCALAPACK routine PSSYEVD with several threads, only the first MPI task is actually threading as expected.

I have met this issue on both my laptop and on a supercomputer, both running with MKL 2019.2.

In practice, the "top" command on my laptop when running with 2 MPI tasks and 2 MKL threads shows that the first MPI task runs at 200%, whereas the second one runs at 100%.

Note that this problem disappear when I call the double precision routine PDSYEVD instead or when I call the more regular PSSYEV.

Best,

Fabien