[Pw_forum] pw.x parallelisation

[Ullah, Habib]

Dear all

We have successfully installed Quantum Espresso on our cluster and calculations with 1 to 7 processors are ok... using example submission scripts as follows and job script as attached: But when increase the processor from 7, then the calculations stop without any error, although our cluster can run a simulation with 120 processors (in case of Metlab).

#!/bin/bash
#$ -N qe
#$ -q all.q
#$ -cwd
# Send mail at submission and completion of script
#$ -m be
#$ -M hu203 at exeter.ac.uk
# Parallel Job
#$ -pe openmpi_ib 7
. /etc/profile.d/modules.sh
module load shared espresso
cd /home/ISAD/hu203/Test
mpirun pw.x -inp 96BiVO4-001.in > 96BiVO4-001.out

Searching online found this document:

http://www.quantum-espresso.org/wp-content/uploads/Doc/pw_user_guide.pdf

pw.x can run in principle on any number of processors.

Wondering if the following is pertinent to our current problems (or if there is a problem with our Espresso installation on the cluster):

Parallelization on PWs:
* yields good to very good scaling, especially if the number of processors in a pool is a divisor of N3 and Nr3 (the dimensions along the z-axis of the FFT grids, nr3 and nr3s, which coincide for NCPPs);
* requires heavy communications (suitable for Gigabit ethernet up to 4, 8 CPUs at most, specialized communication hardware needed for 8 or more processors );
* yields almost linear reduction of memory per processor with the number of processors in the pool.

We have Mellanox Infiniband cards between servers ... each server has 192GB RAM and 4x 12 Core 2.4GHz AMD processor

Kind regards,
Habib

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