Using the exclusive directive (--exclusive)

During normal usage when you start a session on a node, your job will execute on a single core/slot.

Certain applications are multi-threaded in their nature, which means that they will use more than one core/slot to gain performance.  It is possible that a multi-threaded application will use all of the possible resources on a node (from a core/slot perspective). This will obviously have an impact on other users of the node, who may already be running jobs on the same node. 

Therefore if you are running multi-threaded code you need to ask for exclusive use of a node.  You should bear in mind when using this particular directive (--exclusive), you reserve all of the cores/slots on the node (depending on the node this may be up to 28 slots/cores).

We ask that you don't run anymore than 10 jobs with the (-x) flag at any one time. If you have a need for more resource or wish to discuss this further please email hpc.admin@uea.ac.uk

If you are using an application which is capable of multithreading (examples shown below) then you must use the exclusive flag (-x) in submission scripts or during an interactive/Xinteractive session. As detailed below.

Starting an exclusive access interactive session

interactive -x

Starting an exclusive access Xnteractive session

Xinteractive -x

Using the (-x) directive in a jobsript (Gaussian) 

#!/bin/sh
#SBATCH --mail-type=ALL           #Mail events (NONE, BEGIN, END, FAIL, ALL)
#SBATCH --mail-user=<username>@uea.ac.uk    # Where to send mail
#SBATCH -p short-eth                  #Which queue to use
#SBATCH --exclusive                      # set exclusive use of node
#SBATCH --job-name=gaussian-test_job #Job name
#SBATCH -o gaussian-test-%j.out       #Standard output log
#SBATCH -e gaussian-test-%j.err       #Standard error log
. /etc/profile
module add gaussian/09C01
 g09 gauss_opt.inp

Using the (-x) directive in a jobscript (Stata 15 MP16)

#!/bin/sh
#SBATCH --mail-type=ALL           #Mail events (NONE, BEGIN, END, FAIL, ALL)
#SBATCH --mail-user=<username>@uea.ac.uk    # Where to send mail
#SBATCH -p short-eth                  #Which queue to use
#SBATCH --exclusive                      # set exclusive use of node
#SBATCH --job-name=stata-test_job #Job name
#SBATCH -o stata-test-%j.out       #Standard output log
#SBATCH -e stata-test-%j.err       #Standard error log
. /etc/profile
module add stata/15
stata-mp -b do stata15_example.dostata
 

All of the following applications should be run with the (--exclusive) directive:

  • Stata14/15 MP16
  • Gaussian
  • Gaussview
  • Matlab (Parallel Computing Toolbox)