Programming/Perl

Programming Details

Perl is a family of high-level, general-purpose, interpreted, dynamic programming languages. The languages in this family presently are Perl 5 and Perl 6.

When programming with Perl in a HPC environment you will need to change the first line from:

 #!/usr/bin/perl

To

 #!/usr/bin/env perl

Programming example

Non MPI program

#!/usr/bin/env perl
#
# VIPER - HPC
# ICTD Department
# Hull University
#
# Written by DBird 25/12/2017

# ---------------- Modules ------------------------------------------

use strict;                             # perform error checking

# ---------------- Variables ----------------------------------------

my ($i);

# -------------------------------------------------------------------
# ---------------- Main Program -------------------------------------
# -------------------------------------------------------------------

for($i = 0; $i < 1000; $i++)
{
        print "A-->$i\n";
}

# ---------------- finish up and exit -------------------------------

exit;

Note this program does not contain any MPI directives and is shown simply for demonstrative purposes. Although PERL does support MPI, it's implementation is quite limited compared to C, C++ and Fortran.

MPI program

#!/usr/bin/env perl
#
# VIPER - HPC
# ICTD Department
# Hull University
#
# Written by DBird 25/12/2017

use Parallel::MPI::Simple;

 MPI_Init();
 my $rank = MPI_Comm_rank(MPI_COMM_WORLD);

 if ($rank == 1) 
{
   my $msg = "Hello, I'm $rank";
   MPI_Send($msg, 0, 123, MPI_COMM_WORLD);
 }
 else 
{
   my $msg = MPI_Recv(1, 123, MPI_COMM_WORLD);
   print "$rank received: '$msg'\n";
 }
 MPI_Finalise();
exit;

Running the program

The program could be executed in the following way for test purposes on the login node:

module load perl/5.24.0
perl testPerl.pl

Batch example

#!/bin/bash

#SBATCH -J openPERL-node
#SBATCH -N 1
#SBATCH --ntasks-per-node 20
#SBATCH -D /home/user/PERL
#SBATCH -o %N.%j.%a.out
#SBATCH -e %N.%j.%a.err
#SBATCH -p compute
#SBATCH --exclusive

echo $SLURM_JOB_NODELIST

module purge
module load perl/5.24.0

export I_MPI_DEBUG=5
export I_MPI_FABRICS=shm:tmi
export I_MPI_FALLBACK=no

perl /home/user/PERL/demoPERL.pl

[username@login01 ~]$ sbatch demoPERL.job
Submitted batch job 289352