myjob.pbs

#!/bin/bash 

#PBS -N assignment1
#PBS -l select=8:mem=6gb:interconnect=myrinet,walltime=00:10:00
#PBS -j oe       

source /etc/profile.d/modules.sh
module purge
module add gcc/4.8.1 openmpi/1.4.3 

NCORES=`qstat -xf $PBS_JOBID | grep List.ncpus | sed 's/^.\{26\}//'`  
cd $PBS_O_WORKDIR  

mpiexec -n $NCORES ./main > output.log