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.

Partition

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.

Walltime(Hours)

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

Default

1 hour

Parameter	#Hours
Min Limit	1 hour
Max Limit	24 hours
Default	1 hour

CPUs(Threads)

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

interactive

8

normal

22

gpu

14

backfill

62

epscor

62

iiplab

26

cfdlab

26

class

30

Partition	Max Limit
interactive	8
normal	22
gpu	14
backfill	62
epscor	62
iiplab	26
cfdlab	26
class	30

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)
interactive	64
normal	240
gpu	50
backfill	3000
epscor	3000
iiplab	175
cfdlab	175
class	490

GPUs

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

0

Max Limit

2

Parameter	#GPU
Min Limit	0
Max Limit	2

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.

Syntax

source <path to bash script file>

Example

source "$HOME/project_a/setup-env.sh"

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.

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.

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.