Job submission and execution

Job Submission

When allocating computational resources for the job, please specify

  1. suitable queue for your job (default is qprod)
  2. number of computational nodes required
  3. number of cores per node required
  4. maximum wall time allocated to your calculation, note that jobs exceeding maximum wall time will be killed
  5. Project ID
  6. Jobscript or interactive switch

Note

Use the qsub command to submit your job to a queue for allocation of the computational resources.

Submit the job using the qsub command:

$ qsub -A Project_ID -q queue -l select=x:ncpus=y,walltime=[[hh:]mm:]ss[.ms] jobscript

The qsub submits the job into the queue, in another words the qsub command creates a request to the PBS Job manager for allocation of specified resources. The resources will be allocated when available, subject to above described policies and constraints. After the resources are allocated the jobscript or interactive shell is executed on first of the allocated nodes.

Note

PBS statement nodes (qsub -l nodes=nodespec) is not supported on Salomon cluster.

Job Submission Examples

$ qsub -A OPEN-0-0 -q qprod -l select=64:ncpus=24,walltime=03:00:00 ./myjob

In this example, we allocate 64 nodes, 24 cores per node, for 3 hours. We allocate these resources via the qprod queue, consumed resources will be accounted to the Project identified by Project ID OPEN-0-0. Jobscript myjob will be executed on the first node in the allocation.

$ qsub -q qexp -l select=4:ncpus=24 -I

In this example, we allocate 4 nodes, 24 cores per node, for 1 hour. We allocate these resources via the qexp queue. The resources will be available interactively

$ qsub -A OPEN-0-0 -q qlong -l select=10:ncpus=24 ./myjob

In this example, we allocate 10 nodes, 24 cores per node, for 72 hours. We allocate these resources via the qlong queue. Jobscript myjob will be executed on the first node in the allocation.

$ qsub -A OPEN-0-0 -q qfree -l select=10:ncpus=24 ./myjob

In this example, we allocate 10 nodes, 24 cores per node, for 12 hours. We allocate these resources via the qfree queue. It is not required that the project OPEN-0-0 has any available resources left. Consumed resources are still accounted for. Jobscript myjob will be executed on the first node in the allocation.

Intel Xeon Phi Co-Processors

To allocate a node with Xeon Phi co-processor, user needs to specify that in select statement. Currently only allocation of whole nodes with both Phi cards as the smallest chunk is supported. Standard PBSPro approach through attributes "accelerator", "naccelerators" and "accelerator_model" is used. The "accelerator_model" can be omitted, since on Salomon only one type of accelerator type/model is available.

The absence of specialized queue for accessing the nodes with cards means, that the Phi cards can be utilized in any queue, including qexp for testing/experiments, qlong for longer jobs, qfree after the project resources have been spent, etc. The Phi cards are thus also available to PRACE users. There's no need to ask for permission to utilize the Phi cards in project proposals.

$ qsub  -A OPEN-0-0 -I -q qprod -l select=1:ncpus=24:accelerator=True:naccelerators=2:accelerator_model=phi7120 ./myjob

In this example, we allocate 1 node, with 24 cores, with 2 Xeon Phi 7120p cards, running batch job ./myjob. The default time for qprod is used, e. g. 24 hours.

$ qsub  -A OPEN-0-0 -I -q qlong -l select=4:ncpus=24:accelerator=True:naccelerators=2 -l walltime=56:00:00 -I

In this example, we allocate 4 nodes, with 24 cores per node (totalling 96 cores), with 2 Xeon Phi 7120p cards per node (totalling 8 Phi cards), running interactive job for 56 hours. The accelerator model name was omitted.

UV2000 SMP

Note

13 NUMA nodes available on UV2000 Per NUMA node allocation. Jobs are isolated by cpusets.

The UV2000 (node uv1) offers 3TB of RAM and 104 cores, distributed in 13 NUMA nodes. A NUMA node packs 8 cores and approx. 247GB RAM (with exception, node 11 has only 123GB RAM). In the PBS the UV2000 provides 13 chunks, a chunk per NUMA node (see Resource allocation policy). The jobs on UV2000 are isolated from each other by cpusets, so that a job by one user may not utilize CPU or memory allocated to a job by other user. Always, full chunks are allocated, a job may only use resources of the NUMA nodes allocated to itself.

 $ qsub -A OPEN-0-0 -q qfat -l select=13 ./myjob

In this example, we allocate all 13 NUMA nodes (corresponds to 13 chunks), 104 cores of the SGI UV2000 node for 72 hours. Jobscript myjob will be executed on the node uv1.

$ qsub -A OPEN-0-0 -q qfat -l select=1:mem=2000GB ./myjob

In this example, we allocate 2000GB of memory on the UV2000 for 72 hours. By requesting 2000GB of memory, 10 chunks are allocated. Jobscript myjob will be executed on the node uv1.

Useful Tricks

All qsub options may be saved directly into the jobscript. In such a case, no options to qsub are needed.

$ qsub ./myjob

By default, the PBS batch system sends an e-mail only when the job is aborted. Disabling mail events completely can be done like this:

$ qsub -m n

Advanced Job Placement

Placement by Name

Note

Not useful for ordinary computing, suitable for node testing/bechmarking and management tasks.

Specific nodes may be selected using PBS resource attribute host (for hostnames):

qsub -A OPEN-0-0 -q qprod -l select=1:ncpus=24:host=r24u35n680+1:ncpus=24:host=r24u36n681 -I

Specific nodes may be selected using PBS resource attribute cname (for short names in cns[0-1]+ format):

qsub -A OPEN-0-0 -q qprod -l select=1:ncpus=24:host=cns680+1:ncpus=24:host=cns681 -I

In this example, we allocate nodes r24u35n680 and r24u36n681, all 24 cores per node, for 24 hours. Consumed resources will be accounted to the Project identified by Project ID OPEN-0-0. The resources will be available interactively.

Placement by Network Location

Network location of allocated nodes in the InifiBand network influences efficiency of network communication between nodes of job. Nodes on the same InifiBand switch communicate faster with lower latency than distant nodes. To improve communication efficiency of jobs, PBS scheduler on Salomon is configured to allocate nodes - from currently available resources - which are as close as possible in the network topology.

For communication intensive jobs it is possible to set stricter requirement - to require nodes directly connected to the same InifiBand switch or to require nodes located in the same dimension group of the InifiBand network.

Placement by InifiBand Switch

Nodes directly connected to the same InifiBand switch can communicate most efficiently. Using the same switch prevents hops in the network and provides for unbiased, most efficient network communication. There are 9 nodes directly connected to every InifiBand switch.

Note

We recommend allocating compute nodes of a single switch when the best possible computational network performance is required to run job efficiently.

Nodes directly connected to the one InifiBand switch can be allocated using node grouping on PBS resource attribute switch.

In this example, we request all 9 nodes directly connected to the same switch using node grouping placement.

$ qsub -A OPEN-0-0 -q qprod -l select=9:ncpus=24 -l place=group=switch ./myjob

Placement by Specific InifiBand Switch

Note

Not useful for ordinary computing, suitable for testing and management tasks.

Nodes directly connected to the specific InifiBand switch can be selected using the PBS resource attribute switch.

In this example, we request all 9 nodes directly connected to r4i1s0sw1 switch.

$ qsub -A OPEN-0-0 -q qprod -l select=9:ncpus=24:switch=r4i1s0sw1 ./myjob

List of all InifiBand switches:

$ qmgr -c 'print node @a' | grep switch | awk '{print $6}' | sort -u
r1i0s0sw0
r1i0s0sw1
r1i1s0sw0
r1i1s0sw1
r1i2s0sw0
...

List of all all nodes directly connected to the specific InifiBand switch:

$ qmgr -c 'p n @d' | grep 'switch = r36sw3' | awk '{print $3}' | sort
r36u31n964
r36u32n965
r36u33n966
r36u34n967
r36u35n968
r36u36n969
r37u32n970
r37u33n971
r37u34n972

Placement by Hypercube Dimension

Nodes located in the same dimension group may be allocated using node grouping on PBS resource attribute ehc_[1-7]d .

Hypercube dimension node_group_key #nodes per group
1D ehc_1d 18
2D ehc_2d 36
3D ehc_3d 72
4D ehc_4d 144
5D ehc_5d 144,288
6D ehc_6d 432,576
7D ehc_7d all

In this example, we allocate 16 nodes in the same hypercube dimension 1 group.

$ qsub -A OPEN-0-0 -q qprod -l select=16:ncpus=24 -l place=group=ehc_1d -I

For better understanding:

List of all groups in dimension 1:

$ qmgr -c 'p n @d' | grep ehc_1d | awk '{print $6}' | sort |uniq -c
     18 r1i0
     18 r1i1
     18 r1i2
     18 r1i3
...

List of all all nodes in specific dimension 1 group:

$ $ qmgr -c 'p n @d' | grep 'ehc_1d = r1i0' | awk '{print $3}' | sort
r1i0n0
r1i0n1
r1i0n10
r1i0n11
...

Job Management

Note

Check status of your jobs using the qstat and check-pbs-jobs commands

$ qstat -a
$ qstat -a -u username
$ qstat -an -u username
$ qstat -f 12345.isrv5

Example:

$ qstat -a

srv11:
                                                            Req'd Req'd   Elap
Job ID          Username Queue    Jobname    SessID NDS TSK Memory Time S Time
--------------- -------- --  |---|---| ------ --- --- ------ ----- - -----
16287.isrv5     user1    qlong    job1         6183   4 64    --  144:0 R 38:25
16468.isrv5     user1    qlong    job2         8060   4 64    --  144:0 R 17:44
16547.isrv5     user2    qprod    job3x       13516   2 32    --  48:00 R 00:58

In this example user1 and user2 are running jobs named job1, job2 and job3x. The jobs job1 and job2 are using 4 nodes, 16 cores per node each. The job1 already runs for 38 hours and 25 minutes, job2 for 17 hours 44 minutes. The job1 already consumed 64 x 38.41 = 2458.6 core hours. The job3x already consumed 0.96 x 32 = 30.93 core hours. These consumed core hours will be accounted on the respective project accounts, regardless of whether the allocated cores were actually used for computations.

Check status of your jobs using check-pbs-jobs command. Check presence of user's PBS jobs' processes on execution hosts. Display load, processes. Display job standard and error output. Continuously display (tail -f) job standard or error output.

$ check-pbs-jobs --check-all
$ check-pbs-jobs --print-load --print-processes
$ check-pbs-jobs --print-job-out --print-job-err
$ check-pbs-jobs --jobid JOBID --check-all --print-all
$ check-pbs-jobs --jobid JOBID --tailf-job-out

Examples:

$ check-pbs-jobs --check-all
JOB 35141.dm2, session_id 71995, user user2, nodes r3i6n2,r3i6n3
Check session id: OK
Check processes
r3i6n2: OK
r3i6n3: No process

In this example we see that job 35141.dm2 currently runs no process on allocated node r3i6n2, which may indicate an execution error.

$ check-pbs-jobs --print-load --print-processes
JOB 35141.dm2, session_id 71995, user user2, nodes r3i6n2,r3i6n3
Print load
r3i6n2: LOAD: 16.01, 16.01, 16.00
r3i6n3: LOAD:  0.01,  0.00,  0.01
Print processes
       %CPU CMD
r3i6n2:  0.0 -bash
r3i6n2:  0.0 /bin/bash /var/spool/PBS/mom_priv/jobs/35141.dm2.SC
r3i6n2: 99.7 run-task
...

In this example we see that job 35141.dm2 currently runs process run-task on node r3i6n2, using one thread only, while node r3i6n3 is empty, which may indicate an execution error.

$ check-pbs-jobs --jobid 35141.dm2 --print-job-out
JOB 35141.dm2, session_id 71995, user user2, nodes r3i6n2,r3i6n3
Print job standard output:
======================== Job start  ==========================
Started at    : Fri Aug 30 02:47:53 CEST 2013
Script name   : script
Run loop 1
Run loop 2
Run loop 3

In this example, we see actual output (some iteration loops) of the job 35141.dm2

Note

Manage your queued or running jobs, using the qhold, qrls, qdel, qsig or qalter commands

You may release your allocation at any time, using qdel command

$ qdel 12345.isrv5

You may kill a running job by force, using qsig command

$ qsig -s 9 12345.isrv5

Learn more by reading the pbs man page

$ man pbs_professional

Job Execution

Jobscript

Note

Prepare the jobscript to run batch jobs in the PBS queue system

The Jobscript is a user made script, controlling sequence of commands for executing the calculation. It is often written in bash, other scripts may be used as well. The jobscript is supplied to PBS qsub command as an argument and executed by the PBS Professional workload manager.

Note

The jobscript or interactive shell is executed on first of the allocated nodes.

$ qsub -q qexp -l select=4:ncpus=24 -N Name0 ./myjob
$ qstat -n -u username

isrv5:
                                                            Req'd Req'd   Elap
Job ID          Username Queue    Jobname    SessID NDS TSK Memory Time S Time
--------------- -------- --  |---|---| ------ --- --- ------ ----- - -----
15209.isrv5     username qexp     Name0        5530   4 96    --  01:00 R 00:00
   r21u01n577/0*24+r21u02n578/0*24+r21u03n579/0*24+r21u04n580/0*24

In this example, the nodes r21u01n577, r21u02n578, r21u03n579, r21u04n580 were allocated for 1 hour via the qexp queue. The jobscript myjob will be executed on the node r21u01n577, while the nodes r21u02n578, r21u03n579, r21u04n580 are available for use as well.

Note

The jobscript or interactive shell is by default executed in home directory

$ qsub -q qexp -l select=4:ncpus=24 -I
qsub: waiting for job 15210.isrv5 to start
qsub: job 15210.isrv5 ready

$ pwd
/home/username

In this example, 4 nodes were allocated interactively for 1 hour via the qexp queue. The interactive shell is executed in the home directory.

Note

All nodes within the allocation may be accessed via ssh. Unallocated nodes are not accessible to user.

The allocated nodes are accessible via ssh from login nodes. The nodes may access each other via ssh as well.

Calculations on allocated nodes may be executed remotely via the MPI, ssh, pdsh or clush. You may find out which nodes belong to the allocation by reading the $PBS_NODEFILE file

qsub -q qexp -l select=2:ncpus=24 -I
qsub: waiting for job 15210.isrv5 to start
qsub: job 15210.isrv5 ready

$ pwd
/home/username

$ sort -u $PBS_NODEFILE
r2i5n6.ib0.smc.salomon.it4i.cz
r4i6n13.ib0.smc.salomon.it4i.cz
r4i7n0.ib0.smc.salomon.it4i.cz
r4i7n2.ib0.smc.salomon.it4i.cz

$ pdsh -w r2i5n6,r4i6n13,r4i7n[0,2] hostname
r4i6n13: r4i6n13
r2i5n6: r2i5n6
r4i7n2: r4i7n2
r4i7n0: r4i7n0

In this example, the hostname program is executed via pdsh from the interactive shell. The execution runs on all four allocated nodes. The same result would be achieved if the pdsh is called from any of the allocated nodes or from the login nodes.

Example Jobscript for MPI Calculation

Note

Production jobs must use the /scratch directory for I/O

The recommended way to run production jobs is to change to /scratch directory early in the jobscript, copy all inputs to /scratch, execute the calculations and copy outputs to home directory.

#!/bin/bash

# change to scratch directory, exit on failure
SCRDIR=/scratch/work/user/$USER/myjob
mkdir -p $SCRDIR
cd $SCRDIR || exit

# copy input file to scratch
cp $PBS_O_WORKDIR/input .
cp $PBS_O_WORKDIR/mympiprog.x .

# load the mpi module
module load OpenMPI

# execute the calculation
mpiexec -pernode ./mympiprog.x

# copy output file to home
cp output $PBS_O_WORKDIR/.

#exit
exit

In this example, some directory on the /home holds the input file input and executable mympiprog.x . We create a directory myjob on the /scratch filesystem, copy input and executable files from the /home directory where the qsub was invoked ($PBS_O_WORKDIR) to /scratch, execute the MPI programm mympiprog.x and copy the output file back to the /home directory. The mympiprog.x is executed as one process per node, on all allocated nodes.

Note

Consider preloading inputs and executables onto shared scratch before the calculation starts.

In some cases, it may be impractical to copy the inputs to scratch and outputs to home. This is especially true when very large input and output files are expected, or when the files should be reused by a subsequent calculation. In such a case, it is users responsibility to preload the input files on shared /scratch before the job submission and retrieve the outputs manually, after all calculations are finished.

Note

Store the qsub options within the jobscript. Use mpiprocs and ompthreads qsub options to control the MPI job execution.

Example Jobscript for MPI Calculation With Preloaded Inputs

Example jobscript for an MPI job with preloaded inputs and executables, options for qsub are stored within the script :

#!/bin/bash
#PBS -q qprod
#PBS -N MYJOB
#PBS -l select=100:ncpus=24:mpiprocs=1:ompthreads=24
#PBS -A OPEN-0-0

# change to scratch directory, exit on failure
SCRDIR=/scratch/work/user/$USER/myjob
cd $SCRDIR || exit

# load the mpi module
module load OpenMPI

# execute the calculation
mpiexec ./mympiprog.x

#exit
exit

In this example, input and executable files are assumed preloaded manually in /scratch/$USER/myjob directory. Note the mpiprocs and ompthreads qsub options, controlling behavior of the MPI execution. The mympiprog.x is executed as one process per node, on all 100 allocated nodes. If mympiprog.x implements OpenMP threads, it will run 24 threads per node.

HTML commented section #2 (examples need to be reworked)

Example Jobscript for Single Node Calculation

Note

Local scratch directory is often useful for single node jobs. Local scratch will be deleted immediately after the job ends. Be very careful, use of RAM disk filesystem is at the expense of operational memory.

Example jobscript for single node calculation, using local scratch on the node:

#!/bin/bash

# change to local scratch directory
cd /lscratch/$PBS_JOBID || exit

# copy input file to scratch
cp $PBS_O_WORKDIR/input .
cp $PBS_O_WORKDIR/myprog.x .

# execute the calculation
./myprog.x

# copy output file to home
cp output $PBS_O_WORKDIR/.

#exit
exit

In this example, some directory on the home holds the input file input and executable myprog.x . We copy input and executable files from the home directory where the qsub was invoked (\(PBS_O_WORKDIR) to local scratch /lscratch/\)PBS_JOBID, execute the myprog.x and copy the output file back to the /home directory. The myprog.x runs on one node only and may use threads.