Launching interactive apps#

The ‘Interactive Apps’ menu shows a range of different apps that provide a GUI. When you launch an interactive app, Open OnDemand first submits an interactive job to the cluster in your account. Once the interactive job starts, the app is automatically launched inside the interactive session.

To launch an interactive app, you need to fill out the resources form. Most of the options in the resources form are shared across all apps and are explained below. The app-specific options will be detailed in their respective sections. See also the section on choosing your resources for resources recommendations. Beware that launching an app will cause your interactive job to end up in a regular queue, so requesting a large amount of resources might result in a long queue time.

Once you’ve specified all your resources, press the Launch button and your job will be queued.

Table 2 Shared resources (part 1)#
Resource	Description
Cluster	Select one of the supported clusters.
Partition	Select a supported partition in the selected cluster.
Number of hours	Select the time limit (in hours) for your interactive app session.
Number of nodes	Select the number of nodes. Only 1 node should be used in most cases, unless you are sure the app can and will use more than 1 node effectively.
Number of cores	Select the number of cores per node.
Number of GPUs	Select the number of GPUs per node. Check the Tier-2 Infrastructure section for the device type that corresponds to the selected cluster/partition. Only request a GPU if you are sure the app can and will use the GPU effectively.
Pre-run scriptlet	Add optional shell commands to your job before launching the app. For example, loading extra modules that you need within the app, sourcing a specific script, or defining specific environment variables.

Warning

Be careful when using the Pre-run scriptlet, because you will be modifying the behavior of your session.

KU Leuven/UHasselt

Table 3 Shared resources (part 2)#
Resource	Description
Account	Select the credit account you want to deduct the credits from. The accounts associated with your VSC-id will be displayed in a drop-down menu.
Required memory per core in megabytes	This defaults to 3400 MB.
Reservation	If you are part of a reservation, you can also use these nodes with Open Ondemand by specifying your reservation name here.
Screen resolution	For apps which run inside a remote noVNC desktop (e.g. MATLAB, ParaView, etc), one may choose a resolution between ‘FullHD’, ‘2K’ or ‘4K’. After launching the app, one may still change the compression level and the image quality of the transferred noVNC frames. E.g. opting for the lowest compression level and highest image quality can give you a crisp noVNC desktop.
View Only (Share-able Link)	For noVNC apps, you can provide a view-only access to other VSC users. For that, click on the ‘View Only (Share-able Link)’ button to copy the URL into your clipboard, and be able to share it with others.

Note

The acquired GPU will be the same as the type specified in the partition (e.g. a NVIDIA H100 for gpu_h100 on wICE). For wICE, you can also request a GPU from the interactive partition. One GPU here is a virtual GPU slice of the available A100 GPUs. One GPU slice is the same as 1/7th of CUDA cores and memory of an A100 GPU. The interactive partition only allows you to request max 1 GPU (slice) though.

Warning

As the end-user, you are responsible for all consequences of sharing your application with other VSC users. So, think twice before sharing your sensitive data, sources and information by all means.

VUB

Table 4 Shared resources (part 2)#
Resource	Description
Working Directory	Specify the working directory for your app, or use the handy `Select Path` button below the text field to select it from a file browser.

Choosing your resources#

Choosing the correct resources for your interactive session is mostly the same as selecting them when launching regular batch jobs. For this reason, we strongly recommend consulting the documentation on how to effectively choose your job resources:

KU Leuven/UHasselt

Documentation on resources is available for both Genius and wICE.

In most cases we recommend using the interactive partition on wICE for the interactive apps. This partition is meant for lighter work, like code development, testing, debugging, visualisations, pre- and post-processing. Using this partition is also free, mainly to encourage you to request these resources for such work, instead of using any of the other partitions. There are however some limitations on the amount of resources you can request here:

Max 1 node
Max 8 cores
Max 1 virtual GPU slice
Max 16h of walltime

This is put in place to ensure that these resources are kept for their original purpose, namely the interactive work.

If for some reason some of these limitations are too strict for you, or you need resources that are not available on the interactive nodes (e.g. a full GPU, big memory nodes), you can always request nodes from another partition. Remember however that these interactive apps are not meant for running full jobs. If you indeed need multiple nodes or full GPUs to test your code/program, go ahead and request the resources for your interactive app from a more suitable partition.

If requesting a GPU, it will be the same as the type specified in the partition (e.g. a NVIDIA H100 for gpu_h100 on wICE). For wICE, you can also request a GPU from the interactive partition. One GPU here is a virtual GPU slice of the available A100 GPUs. One GPU slice is the same as 1/7th of CUDA cores and memory of an A100 GPU. The interactive partition only allows you to request max 1 GPU (slice) though.

VUB

Documentation on resources is available in the section on job submission.

For light-weight (testing) work, we recommend using the Anansi Cluster, which also contains shared GPUs for improved rendering performance.

Once you have passed the testing phase, and you want to start conducting experiments, we recommend that you make the switch to batch jobs instead, as they will not require your presence to start your code.