I'm new here so forgive me if I ask any dumb questions. But the first question I have concerns the mpirun script below.

My question is, what does the SYNCLOC=/bin/sync line for in the script below do, and what complications could arise (if any), from disabling this option by commenting out the line like #SYNCLOC=/bin/sync. In some code we are running, we have found that disabling this option allows high priority jobs to complete in only a couple of seconds, whereas before they would take several minutes.

What does SYNCLOC do, and if its disabled, what kind of problems might that cause?

#! /bin/sh 

# MPIRUN for MPICH
# (Don't change the above line - we use it to identify MPICH mpirun as
# opposed to others (e.g., SGI's mpirun)


#
# This script tries to start jobs on whatever kind of machine you're on.
# Strategy - This program is built with a default device it uses in
# certain ways. The user can override this default from the command line.


#
# This sh script is designed to use other scripts to provide the commands
# to run each system, using the . filename.sh mechanism
#
# Debuggers should be handled by running 
# mpirun.db.<debugger_name>


# e.g., mpirun.db.gdb or mpirun.db.xxgdb.
# This will allow users to add there own debuggers 
# (with -debug=<debugger_name>)
#
# Set default variables
AUTOMOUNTFIX="sed -e s@/tmp_mnt/@/@g"


DEFAULT_DEVICE=ch_p4
RSHCOMMAND="/usr/bin/ssh"
SYNCLOC=/bin/sync     # <---------- WE DISABLED THIS WITH A #COMMENT#
CC="cc"
COMM=

GLOBUSDIR=@GLOBUSDIR@

CLINKER="cc"
prefix=/cluster/cairo/software/mpich-1.2.5.2
bindir=/cluster/cairo/software/mpich-1.2.5.2/bin
# This value for datadir is the default value setup by configure

datadir=/cluster/cairo/software/mpich-1.2.5.2/share

DEFAULT_MACHINE=ch_p4
DEFAULT_ARCH=LINUX

# Derived variables
MPIRUN_BIN=$bindir
MPIRUN_HOME=$MPIRUN_BIN
MPIVERSION="1.2.5 (release) of : 2003/01/13 16:21:53"


#set verbose
#
# Local routines

#
# End of routine

#
#
# Special, system specific values
#
# polling_mode is for systems that can select between polling and 
# interrupt-driven operation.  Currently, only IBM POE is so supported


# (TMC CMMD has some support for this choice of mode)
polling_mode=1

# Parse command line arguments
# The ultimate goal is to determine what kind of parallel machine this
# is we are running on. Then we know how to start jobs...


#
# Process common arguments (currently does ALL, but should pass unrecognized
# ones to called files)
#
hasprinthelp=1
. $MPIRUN_HOME/mpirun.args
argsset=1

#
# Jump to the correct code for the device (by pseudo machine)


#
mpirun_version=""
case $machine in
    ch_cmmd)
	mpirun_version=$MPIRUN_HOME/mpirun.ch_cmmd
	;;
    ibmspx|ch_eui|ch_mpl)
	mpirun_version=$MPIRUN_HOME/mpirun.ch_mpl
	;;
    anlspx)


	mpirun_version=$MPIRUN_HOME/mpirun.anlspx
	;;
    ch_meiko|meiko)
	mpirun_version=$MPIRUN_HOME/mpirun.meiko
	;;
    cray_t3d|t3d)
	mpirun_version=$MPIRUN_HOME/mpirun.t3d
	;;
    ch_nc)
	mpirun_version=$MPIRUN_HOME/mpirun.ch_nc


	;;
    paragon|ch_nx|nx)
	mpirun_version=$MPIRUN_HOME/mpirun.paragon
	;;
    inteldelta)
	mpirun_version=$MPIRUN_HOME/mpirun.delta
	;;
    i860|ipsc860)
	mpirun_version=$MPIRUN_HOME/mpirun.i860


	;;
    p4|ch_p4|sgi_mp)
	mpirun_version=$MPIRUN_HOME/mpirun.ch_p4
	;;
    gm|ch_gm|myrinet)
        mpirun_version=$MPIRUN_HOME/mpirun.ch_gm
	;;
    execer)
	mpirun_version=$MPIRUN_HOME/mpirun.execer


	;;
    ch_shmem|ch_spp|smp|convex_spp)
	# sgi_mp is reserved for the p4 version
	mpirun_version=$MPIRUN_HOME/mpirun.ch_shmem
    	;;
    ksr|symm_ptx)
	mpirun_version=$MPIRUN_HOME/mpirun.p4shmem

	;;

    ch_tcp|tcp)
	mpirun_version=$MPIRUN_HOME/mpirun.ch_tcp
	;;
    globus)
	mpirun_version=$MPIRUN_HOME/mpirun.globus
	;;
    *)    
	#
	# This allows us to add a device without changing the base mpirun


	# code
	if [ -x $MPIRUN_HOME/mpirun.$device ] ; then
	    mpirun_version=$MPIRUN_HOME/mpirun.$device
	elif [ -x $MPIRUN_HOME/mpirun.$default_device ] ; then
	    mpirun_version=$MPIRUN_HOME/mpirun.$default_device


	    device=$default_device
	else
	    echo "Cannot find MPIRUN machine file for machine $machine"
	    echo "and architecture $arch ."
            if [ -n "$device" ] ; then

	        echo "(Looking for $MPIRUN_HOME/mpirun.$device)"

	    else
	        echo "(No device specified.)"
            fi
	    # . $MPIRUN_HOME/mpirun.default
	    exit 1
	fi
  	;;

esac
exitstatus=1
if [ -n "$mpirun_version" ] ; then

    if [ -x $mpirun_version ] ; then
        # The mpirun script *must* set exitstatus (or exit itself)
        . $mpirun_version
    else

       	echo "$mpirun_version is not available."
	    exit 1

    fi
else
    echo "No mpirun script for this configuration!"
    exit 1
fi
exit $exitstatus

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