Nwchem problems in Ubuntu 20.04 LTS when it runs in parallel.
Clicked A Few Times
3:24:46 PM PDT - Tue, May 26th 2020
Hi all

I have compiled Nwchem under the new linux Ubuntu-20.04. with Openblas 32 and 64 bit that I have installed from the Ubuntu repository. I have perform some compilation tests with the Openblas 32bit and then 64bit library. Once compiled I did optimization tests on a small molecule (Methylamine)

The program worked correctly in serial mode with 32 and 64 bit openblas library:

$ nwchem methylamine,nw > methylamine.out

Task times cpu: 513.8s wall: 149.9s

But it failed in parallel mode:

$ mpirun -np 8 nwchem methylamine.nw > methylamine.out

The calculation runs indefinitely and I have to stop aborting it. In the output file everything stops at the part that says the following:


                          NWChem Geometry Optimization

                          ----------------------------






                          Methylamine Opt B3LYP/6-31G*


Ubuntu 20.04 LTS

gcc version 9.3.0
gfortran version 9.3.0
libopenmpi version 4.0.3
libopenblas, libopenblas64 serial and parallel version 0.3.8

Forum Vet
9:38:34 AM PDT - Wed, May 27th 2020
One cause of this behavior might be the incompatibility between mpirun and the MPI libraries used during the compilation ... Can you verify that?

Clicked A Few Times
5:43:22 PM PDT - Wed, May 27th 2020
Problem solved
Hi

I have added at /home/manager/.profile the following three lines:

export OMP_NUM_THREADS=1
export OPENBLAS_NUM_THREADS=1
export GOTO_NUM_THREADS=1

And the problem gone.

This is the times for serial run:
Total times  cpu:      523.7s     wall:      148.2s

This is the times for parallel run with "mpirun -np 8"
Total times  cpu:       45.8s     wall:       49.1s
Best Regards...


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