Interactive MatLab

Opening MatLab Form

  • The first step is to select the Interactive apps and then click the MatLab GUI in the Open OnDemand dashboard.

  • Then you will see a form which needs to be filled to launch the MatLab GUI on compute nodes.

MatLab Form


  • Partitions are work queues that has computational nodes in it to run the jobs. The partitions available in Discovery are interactive,normal, gpu, backfill, class, epscor, iiplab, cfdlab, so on.

  • However, you will see only the list of authorized partitions available for your Discovery account and hence, you won’t see the partitions which you don’t have authorization in the select dropdown.

  • Select one of the partitions where you want to submit your job. Refer to the page → Partitions in Discovery to select the ideal partition for your job.

  • By Default, partition is set to interactive.

  • Backfill partition is also enabled to launch MatLab GUI through the interactive session. However, jobs on Backfill are subject to being stopped and requeued. Hence, you need to fill the last form field with the MatLab command if you want to launch MatLab in Backfill.

MatLab Command


  • Sets the Walltime for your job. The job gets killed if the Walltime you set gets elapsed.

    Parameter #Hours

    Min Limit

    1 hour

    Max Limit

    24 hours


    1 hour


  • Sets the Number of CPUs(Threads) for the job. The below table shows the maximum limit for CPU threads for each partition. The default and minimum value is 1 CPU thread.

    Partition Max Limit

















  • MatLab Parallel Kit, or workers, requires Simultaneous Multithreading(SMT)/HT to be disabled. Hence, SMT is disabled for MatLab by default.

Memory (GB/Gigabytes)

  • Sets the memory for the job in terms of GB. The memory you select is available to all assigned threads for the job. The below table shows the maximum memory limit for each partition which can be requested for the job. The default and minimum value is 1 GB.

Partition Max Memory Limit(GB)


















  • To enable the GPU selection, you need to choose one of the following partitions: interactive, class, gpu, epscor, iiplab, cfdlab. Only these partitions have GPUs and if you select any of the partitions, you can see the GPUs dropdown enabled.

    Parameter #GPU

    Min Limit


    Max Limit


Partition normal don’t have GPUs.

Email Address

  • If you want to get notified via email when the job starts/fails/ends, enter the email address associated with the Discovery account.

  • You can leave the text field blank if you don’t want job notifications.

MatLab version

  • Select one of the available versions 2021a,2020a, 2018a,2017b from the dropdown for the MatLab software.

  • By Default, MatLab version 2017b is selected.

Setup Commands(bash syntax)

You can use the text entry box to enter setup commands which will run before MatLab GUI gets launched. Some useful setup commands are,

  • Load Additional Modules?

  • Source a Bash Script

To load additional modules, use the module load command to load into your working environment.

module load <software-name>

For more information about module load command , refer to the page → Module Load in Discovery.

You can also source a bash script which will read and execute commands from the file specified as its argument.


source <path to bash script file>


source "$HOME/project_a/"

Launching the Interactive Session

  • Once all the form fields are set, you can click the Launch button. The interactive session will be launched and you will see the below output.

MatLab Output
  • The above output shows that the interactive MatLab session has been launched successfully. You will see the Launch MatLab only if the resources you have requested becomes available. Else, you might need to wait for some more minutes for the resources allocation and then the Launch MatLab button appears.

  • You can also set the Compression and Image Quality for MatLab GUI by using the slider. After setting the values, click the Launch MatLab button.

The interactive session won’t be launched if you try to submit your job to the partition that you don’t have access to. You will get the following error message → Batch job submission failed: User’s group not permitted to use this partition. Also, the page gets reloaded and you need to select the value for the form fields again since the form gets reset.

Opening MatLab Graphical User Interface

  • On clicking the Launch MatLab button, the MatLab GUI opens in a new tab through a VNC session.

  • The above output shows that the MatLab GUI has been launched on the compute nodes in the Discovery through a VNC session.

  • Also, you have four different workspaces which is highlighted in red color in the top right corner of the window and you can use it.

  • Furthermore, you have Applications tab and you will see the following applications → Web Browser, File Manager, Terminal Emulator which you can open and use it.

Killing the Interactive Session

  • To kill the interactive session, you can simply press the close icon of the MatLab GUI window. This will close the session and the cluster resources get freed.

  • Another way to kill the session is to go to the My Interactive sessions tab and select the Delete button of the current interactive session.

MatLab delete session

Whenever you are done with the work, it’s always recommended to kill/delete the interactive session running on the compute nodes and free the resources.