# 10.10. Launching with Grid Engine

Open MPI supports the family of run-time schedulers including the Sun Grid Engine (SGE), Oracle Grid Engine (OGE), Grid Engine (GE), Son of Grid Engine, and others.

This documentation will collectively refer to all of them as “Grid Engine”, unless a referring to a specific flavor of the Grid Engine family.

## 10.10.1. Verify Grid Engine support

Important

To build Grid Engine support in Open MPI, you will need to explicitly request the SGE support with the `--with-sge` command line switch to Open MPI’s `configure` script.

To verify if support for Grid Engine is configured into your Open MPI installation, run `prte_info` as shown below and look for `gridengine`.

    shell$ prte_info | grep gridengine
                  MCA ras: gridengine (MCA v2.0, API v2.0, Component v1.3)

Note

PRRTE is the software layer that provides run-time environment support to Open MPI. Open MPI typically hides most PMIx and PRRTE details from the end user, but this is one place that Open MPI is unable to hide the fact that PRRTE provides this functionality, not Open MPI. Hence, users need to use the `prte_info` command to check for Grid Engine support (not `ompi_info`).

## 10.10.2. Launching

When Grid Engine support is included, Open MPI will automatically detect when it is running inside SGE and will just “do the Right Thing.”

Specifically, if you execute an `mpirun` command in a Grid Engine job, it will automatically use the Grid Engine mechanisms to launch and kill processes. There is no need to specify what nodes to run on — Open MPI will obtain this information directly from Grid Engine and default to a number of processes equal to the slot count specified. For example, this will run 4 MPI processes on the nodes that were allocated by Grid Engine:

    # Get the environment variables for Grid Engine

    # (Assuming Grid Engine is installed at /opt/sge and $Grid
    # Engine_CELL is 'default' in your environment)
    shell$ . /opt/sge/default/common/settings.sh

    # Allocate an Grid Engine interactive job with 4 slots from a
    # parallel environment (PE) named 'ompi' and run a 4-process Open
    # MPI job
    shell$ qrsh -pe ompi 4 -b y mpirun -n 4 mpi-hello-world

There are also other ways to submit jobs under Grid Engine:

    # Submit a batch job with the 'mpirun' command embedded in a script
    shell$ qsub -pe ompi 4 my_mpirun_job.csh

    # Submit a Grid Engine and OMPI job and mpirun in one line
    shell$ qrsh -V -pe ompi 4 mpirun hostname

    # Use qstat(1) to show the status of Grid Engine jobs and queues
    shell$ qstat -f

In reference to the setup, be sure you have a Parallel Environment (PE) defined for submitting parallel jobs. You don’t have to name your PE “ompi”. The following example shows a PE named “ompi” that would look like:

    shell$ qconf -sp ompi
       pe_name            ompi
       slots              99999
       user_lists         NONE
       xuser_lists        NONE
       start_proc_args    NONE
       stop_proc_args     NONE
       allocation_rule    $fill_up
       control_slaves     TRUE
       job_is_first_task  FALSE
       urgency_slots      min
       accounting_summary FALSE
       qsort_args         NONE

Note

`qsort_args` is necessary with the Son of Grid Engine distribution, version 8.1.1 and later, and probably only applicable to it.

Note

For very old versions of Sun Grid Engine, omit `accounting_summary` too.

You may want to alter other parameters, but the important one is `control_slaves`, specifying that the environment has “tight integration”. Note also the lack of a start or stop procedure. The tight integration means that mpirun automatically picks up the slot count to use as a default in place of the `-n` argument, picks up a host file, spawns remote processes via `qrsh` so that Grid Engine can control and monitor them, and creates and destroys a per-job temporary directory (`$TMPDIR`), in which Open MPI’s directory will be created (by default).

Be sure the queue will make use of the PE that you specified:

    shell$ qconf -sq all.q
    [...snipped...]
    pe_list               make cre ompi
    [...snipped...]

To determine whether the Grid Engine parallel job is successfully launched to the remote nodes, you can pass in the MCA parameter `--mca plm_base_verbose 1` to `mpirun`.

This will add in a `-verbose` flag to the `qrsh -inherit` command that is used to send parallel tasks to the remote Grid Engine execution hosts. It will show whether the connections to the remote hosts are established successfully or not.

Error

TODO is this site still live? Doesn’t look like it.. Jeff emailed Dave Love on 31 Dec 2021 to ask if this is still the correct URL.

Update March 2022: it doesn’t look like this web site is good any more. Perhaps use https://github.com/grisu48/gridengine instead…?

Various Grid Engine documentation with pointers to more is available at the Son of GridEngine site, and configuration instructions can be found at the Son of GridEngine configuration how-to site.

## 10.10.3. Grid Engine tight integration support of the `qsub -notify` flag

If you are running SGE 6.2 Update 3 or later, then the `-notify` flag is supported. If you are running earlier versions, then the `-notify` flag will not work and using it will cause the job to be killed.

To use `-notify`, one has to be careful. First, let us review what `-notify` does. Here is an excerpt from the qsub man page for the `-notify` flag.

> The `-notify` flag, when set causes Sun Grid Engine to send warning signals to a running job prior to sending the signals themselves. If a SIGSTOP is pending, the job will receive a SIGUSR1 several seconds before the SIGSTOP. If a SIGKILL is pending, the job will receive a SIGUSR2 several seconds before the SIGKILL. The amount of time delay is controlled by the notify parameter in each queue configuration.

Let us assume the reason you want to use the `-notify` flag is to get the SIGUSR1 signal prior to getting the SIGTSTP signal. Something like this batch script can be used:

    #! /bin/bash
    #$ -S /bin/bash
    #$ -V
    #$ -cwd
    #$ -N Job1
    #$ -pe ompi 16
    #$ -j y
    #$ -l h_rt=00:20:00
    mpirun -n 16 -mca orte_forward_job_control 1 mpi-hello-world

Error

Ralph: Does `orte_forward_job_control` still exist?

However, one has to make one of two changes to this script for things to work properly. By default, a SIGUSR1 signal will kill a shell script. So we have to make sure that does not happen. Here is one way to handle it:

    #! /bin/bash
    #$ -S /bin/bash
    #$ -V
    #$ -cwd
    #$ -N Job1
    #$ -pe ompi 16
    #$ -j y
    #$ -l h_rt=00:20:00
    exec mpirun -n 16 -mca orte_forward_job_control 1 mpi-hello-world

Alternatively, one can catch the signals in the script instead of doing an exec on the mpirun:

    #! /bin/bash
    #$ -S /bin/bash
    #$ -V
    #$ -cwd
    #$ -N Job1
    #$ -pe ompi 16
    #$ -j y
    #$ -l h_rt=00:20:00

    function sigusr1handler()
    {
        echo "SIGUSR1 caught by shell script" 1>&2
    }

    function sigusr2handler()
    {
        echo "SIGUSR2 caught by shell script" 1>&2
    }

    trap sigusr1handler SIGUSR1
    trap sigusr2handler SIGUSR2

    mpirun -n 16 -mca orte_forward_job_control 1 mpi-hello-world

## 10.10.4. Grid Engine job suspend / resume support

To suspend the job, you send a SIGTSTP (not SIGSTOP) signal to `mpirun`. `mpirun` will catch this signal and forward it to the `mpi-hello-world` as a SIGSTOP signal. To resume the job, you send a SIGCONT signal to `mpirun` which will be caught and forwarded to the `mpi-hello-world`.

By default, this feature is not enabled. This means that both the SIGTSTP and SIGCONT signals will simply be consumed by the `mpirun` process. To have them forwarded, you have to run the job with `--mca orte_forward_job_control 1`. Here is an example on Solaris:

Error

TODO Ralph: does `orte_forward_job_control` still exist?

    shell$ mpirun -mca orte_forward_job_control 1 -n 2 mpi-hello-world

In another window, we suspend and continue the job:

    shell$ prstat -p 15301,15303,15305
       PID USERNAME  SIZE   RSS STATE  PRI NICE      TIME  CPU PROCESS/NLWP
     15305 rolfv     158M   22M cpu1     0    0   0:00:21 5.9% mpi-hello-world/1
     15303 rolfv     158M   22M cpu2     0    0   0:00:21 5.9% mpi-hello-world/1
     15301 rolfv    8128K 5144K sleep   59    0   0:00:00 0.0% mpirun/1

    shell$ kill -TSTP 15301
    shell$ prstat -p 15301,15303,15305
       PID USERNAME  SIZE   RSS STATE  PRI NICE      TIME  CPU PROCESS/NLWP
     15303 rolfv     158M   22M stop    30    0   0:01:44  21% mpi-hello-world/1
     15305 rolfv     158M   22M stop    20    0   0:01:44  21% mpi-hello-world/1
     15301 rolfv    8128K 5144K sleep   59    0   0:00:00 0.0% mpirun/1

    shell$ kill -CONT 15301
    shell$ prstat -p 15301,15303,15305
       PID USERNAME  SIZE   RSS STATE  PRI NICE      TIME  CPU PROCESS/NLWP
     15305 rolfv     158M   22M cpu1     0    0   0:02:06  17% mpi-hello-world/1
     15303 rolfv     158M   22M cpu3     0    0   0:02:06  17% mpi-hello-world/1
     15301 rolfv    8128K 5144K sleep   59    0   0:00:00 0.0% mpirun/1

Note that all this does is stop the `mpi-hello-world` processes. It does not, for example, free any pinned memory when the job is in the suspended state.

To get this to work under the Grid Engine environment, you have to change the `suspend_method` entry in the queue. It has to be set to SIGTSTP. Here is an example of what a queue should look like.

    shell$ qconf -sq all.q
    qname                 all.q
    [...snipped...]
    starter_method        NONE
    suspend_method        SIGTSTP
    resume_method         NONE

Note that if you need to suspend other types of jobs with SIGSTOP (instead of SIGTSTP) in this queue then you need to provide a script that can implement the correct signals for each job type.