If you want to re-direct standard output of MPI result on vector node of SQUID, please use the script "/opt/nec/ve/bin/mpisep.sh".
How to use this script is the following:
#PBS -v MPISEPSELECT=3
mpirun -np 160 /opt/nec/ve/bin/mpisep.sh ./a.out
In the case, the standard output is output to stdout.0:(MPI process ID), and the standard error output is output to stderr.0:(MPI process ID) in real time.
Please see "3.3" of the following manual about the detail:
NEC MPI User's guide
If you modified mpisep.sh, you change stdout/stderr filename into whatever you want to name.