Batch Jobs - bwUniCluster Features

This article contains information on features of the batch job system only applicable on bwUniCluster.

Job Submission

msub Command

The bwUniCluster supports the following additional msub option(s):

bwUniCluster additional msub Options
Command line	Script	Purpose
-I		Declares the job is to be run interactively.

msub -l resource_list

No deviation or additional features to general batch job setting.

msub -q queues

Compute resources such as walltime, nodes and memory are restricted and must fit into queues. Since requested compute resources are NOT always automatically mapped to the correct queue class, you must add to your msub command the correct queue class. Details are:

msub -q queue
queue	node	default resources	minimum resources	maximum resources	node access policy
develop	thin	walltime=00:10:00,procs=1, pmem=4000mb	nodes=1	nodes=1:ppn=16, walltime=00:30:00	shared
singlenode	thin	walltime=00:30:01,procs=1, pmem=4000mb	nodes=1, walltime=00:30:01	nodes=1:ppn=16, walltime=3:00:00:00	shared
multinode	thin	walltime=00:10:00,procs=1, pmem=4000mb	nodes=2	nodes=16:ppn=16, walltime=2:00:00:00	singlejob
verylong	thin	walltime=3:00:00:01,procs=1, pmem=4000mb	nodes=1, walltime=3:00:00:01	nodes=1:ppn=16, walltime=6:00:00:00	shared
fat	fat	walltime=00:10:00,procs=1, pmem=32000mb	nodes=1	nodes=1:ppn=32, walltime=3:00:00:00	shared

Note that node access policy=singlejob means that, irrespected of the requested number of cores, node access is exclusive. Default resources of a queue class defines walltime, processes and memory if not explicitly given with msub command. Resource list acronyms walltime, procs, nodes and ppn are described here.

Queue class examples

• To run your batch job longer than 3 days, please use$ msub -q verylong.

• To run your batch job on one of the fat nodes, please use$ msub -q fat.

Environment Variables for Batch Jobs

The bwUniCluster expands the common set of MOAB environment variables by the following variable(s):

bwUniCluster specific MOAB variables
Environment variables	Description
MOAB_SUBMITDIR	Directory of job submission

Since the work load manager MOAB on bwUniCluster uses the resource manager SLURM, the following environment variables of SLURM are added to your environment once your job has started:

SLURM variables
Environment variables	Description
SLURM_JOB_CPUS_PER_NODE	Number of processes per node dedicated to the job
SLURM_JOB_NODELIST	List of nodes dedicated to the job
SLURM_JOB_NUM_NODES	Number of nodes dedicated to the job
SLURM_MEM_PER_NODE	Memory per node dedicated to the job
SLURM_NPROCS	Total number of processes dedicated to the job

Interactiv Job Monitoring per Node

By default nodes are not used exclusive unless they are requested with -l naccesspolicy=singlejob as described here.
If a Job runs exclusive on one node you may do a ssh login to that node. The ssh access will be limited by the set walltime. To get the nodes of your job need to read the environment variable SLURM_JOB_NODELIST during the runtime of the job. It contains all nodes in a shortened way e.g. uc1n[344,386] or uc1n[344-345]. To expand this string to uc1n344 uc1n345 you can you can use the command expandnodes like:

 expandnodes $SLURM_JOB_NODELIST > nodelist

Intel MPI parallel Programs

Intel MPI without Multithreading

MPI parallel programs run faster than serial programs on multi CPU and multi core systems. N-fold spawned processes of the MPI program, i.e., MPI tasks, run simultaneously and communicate via the Message Passing Interface (MPI) paradigm. MPI tasks do not share memory but can be spawned over different nodes.

Generate a wrapper script for Intel MPI, job_impi.sh containing the following lines:

#!/bin/bash
module load mpi/impi/<placeholder_for_version>
mpiexec.hydra -bootstrap slurm my_par_program

Attention: Do NOT add mpirun options -n <number_of_processes> or any other option defining processes or nodes, since MOAB instructs mpirun about number of processes and node hostnames. Moreover, replace <placeholder_for_version> with the wished version of Intel MPI to enable the MPI environment.

Launching and running 32 Intel MPI tasks on 4 nodes, each requiring 1000 MByte, and running for 5 hours, execute:

$ msub -q multinode -l nodes=4:ppn=16,pmem=1000mb,walltime=05:00:00 job_impi.sh

Intel MPI with Multithreading

Multithreaded + MPI parallel programs operate faster than serial programs on multi CPUs with multiple cores. All threads of one process share resources such as memory. On the contrary MPI tasks do not share memory but can be spawned over different nodes.

Multiple Intel MPI tasks must be launched by the MPI parallel program mpiexec.hydra. For multithreaded programs based on Open Multi-Processing (OpenMP) number of threads are defined by the environment variable OMP_NUM_THREADS. By default this variable is set to 1 (OMP_NUM_THREADS=1).

For Intel MPI a job-script to submit a batch job called job_impi_omp.sh that runs a Intel MPI program with 8 tasks and a tenfold threaded program impi_omp_program requiring 32000 MByte of total physical memory per task and total wall clock time of 6 hours looks like:

#!/bin/bash
#MSUB -l nodes=4:ppn=20
#MSUB -l walltime=06:00:00
#MSUB -l pmem=3200mb
#MSUB -v MPI_MODULE=mpi/impi
#MSUB -v OMP_NUM_THREADS=10
#MSUB -v MPIRUN_OPTIONS="-binding "domain=omp" -print-rank-map -ppn 2 -envall"
#MSUB -v EXE=./impi_omp_program
#MSUB -N test_impi_omp

#If using more than one MPI task per node please set
export KMP_AFFINITY=scatter
#export KMP_AFFINITY=verbose,scatter  prints messages concerning the supported affinity 
#KMP_AFFINITY Description: https://software.intel.com/en-us/node/524790#KMP_AFFINITY_ENVIRONMENT_VARIABLE
 
module load ${MPI_MODULE}
TASK_COUNT=$((${MOAB_PROCCOUNT}/${OMP_NUM_THREADS}))
echo "${EXE} running on ${MOAB_PROCCOUNT} cores with ${TASK_COUNT} MPI-tasks and ${OMP_NUM_THREADS} threads"
startexe="mpiexec.hydra -bootstrap slurm ${MPIRUN_OPTIONS} -n ${TASK_COUNT} ${EXE}"
echo $startexe
exec $startexe

Using Intel compiler the environment variable KMP_AFFINITY switches on binding of threads to specific cores. If you only run one MPI task per node please set KMP_AFFINITY=compact,1,0.

Execute the script job_impi_omp.sh adding the queue class multinode to your msub command:

$ msub -q multinode job_impi_omp.sh

The mpirun option -print-rank-map shows the bindings between MPI tasks and nodes (not very beneficial). The option -binding binds MPI tasks (processes) to a particular processor; domain=omp means that the domain size is determined by the number of threads. In the above examples (2 MPI tasks per node) you could also choose -binding "cell=unit;map=bunch"; this binding maps one MPI process to each socket.

Interactive Jobs

Interactive jobs on bwUniCluster must NOT run on the logins nodes, however resources for interactive jobs can be requested using msub. Considering a serial application with a graphical frontend that requires 5000 MByte of memory and limiting the interactive run to 2 hours execute the following:

$ msub  -I  -V  -l nodes=1:ppn=1 -l walltime=0:02:00:00

The option -V defines that all environment variables are exported to the compute node of the interactive session. After execution of this command DO NOT CLOSE your current terminal session but wait until the queueing system MOAB has granted you the requested resources on the compute system. Once granted you will be automatically logged on the dedicated resource. Now you have an interactive session with 1 core and 5000 MByte of memory on the compute system for 2 hours. Simply execute now your application:

$ cd to_path
$ ./application

Note that, once the walltime limit has been reached you will be automatically logged out of the compute system.

Chain Jobs

The CPU time requirements of many applications exceed the limits of the job classes. In those situations it is recommended to solve the problem by a job chain. A job chain is a sequence of jobs where each job automatically starts its successor.

#!/bin/bash
##################################################
## simple MOAB submitter script to setup        ## 
## a chain of jobs for bwUniCluster             ##
##################################################
## ver.  : 2015-09-17, KIT, SCC

## Define maximum number of jobs via positional parameter 1, default is 5
max_nojob=${1:-5}

## Define your jobscript (e.g. "~/chain_link_job.sh")
chain_link_job=${PWD}/chain_link_job.sh

## Define type of dependency via positional parameter 2, default is 'afterok'
dep_type="${2:-afterok}"
## -> List of all dependencies:
## http://docs.adaptivecomputing.com/suite/8-0/enterprise/help.htm#topics/moabWorkloadManager/topics/jobAdministration/jobdependencies.html

myloop_counter=1
## Submit loop
while [ ${myloop_counter} -le ${max_nojob} ] ; do
   ##
   ## Differ msub_opt depending on chain link number
   if [ ${myloop_counter} -eq 1 ] ; then
      msub_opt=""
   else
      ## Attention: do NOT use '-W depend' together with msub
      msub_opt="-l depend=${dep_type}:${jobID}"
   fi
   ##
   ## Print current iteration number and msub command
   echo "Chain job iteration = ${myloop_counter}"
   echo "   msub -v myloop_counter=${counter} ${msub_opt} ${chain_link_job}"
   ## Store job ID for next iteration by storing output of msub command with empty lines
   jobID=$(msub -v myloop_counter=${counter} ${msub_opt} ${chain_link_job} 2>&1 | sed '/^$/d')
   ##   
   ## Check if ERROR occured
   if [[ "${jobID}" =~ "ERROR" ]] ; then
      echo "   -> submission failed!" ; exit 1
   else
      echo "   -> job number = ${jobID}"
   fi
   ##
   ## Increase counter
   let myloop_counter+=1
done

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