General/Interactive

Introduction

An interactive session can be started on Viper that can be used for any task that requires interaction and should be used for any computationally demanding task rather than using the login node.

Examples for interactive usage include:

• Code compilation
• Data analysis
• Basic visualisation
• Console based interactive applications such as Python, R, Matlab, SAS or Stata
• Graphical user interfaces such as Matlab, SAS or Stata

Interactive Sessions

Starting an interactive session

An interactive session can be started by using the interactive command:

[username@login01 ~]$ interactive
salloc: Granted job allocation 306844
Job ID 306844 connecting to c068, please wait...
[username@c068 ~]$

To exit from an interactive session just type exit:

[username@c068 ~]$ exit
logout
salloc: Relinquishing job allocation 306844
[username@login01 ~]$ 

By default the interactive command will give you an allocation to a single compute core on a node for 12 hours and a standard 4GB of RAM. This can be adjusted in the following ways:

Exclusive interactive session

[username@login01 ~]$ interactive --exclusive
salloc: Granted job allocation 306848
Job ID 306848 connecting to c174, please wait...

Note: This will give you the whole node for your job exclusively, if this is not specified there may be other jobs that are running on the allocated node at the same time. For example if you job requires a significant about of processing cores this should be specified, single processing core tasks would not require this and would leave the other process cores idle. (See Interactive session with additional CPU cores below).

Interactive session with additional CPU cores

[username@login01 ~]$ interactive -n24
salloc: Granted job allocation 306849
Job ID 306849 connecting to c174, please wait...

Interactive session with additional RAM

[username@login01 ~]$ interactive --mem=24G
salloc: Granted job allocation 306852
Job ID 306852 connecting to c068, please wait...

Note: if a job exceeds the requested about of memory, it will terminate with an error message similar to the following (a job which ran with a memory limit of 2GB):

slurmstepd: Step 307110.0 exceeded memory limit (23933492 > 2097152), being killed
srun: Job step aborted: Waiting up to 32 seconds for job step to finish.
srun: got SIGCONT
slurmstepd: Exceeded job memory limit

Interactive session using a different partition

[username@login01 ~]$ interactive -phighmem
salloc: Granted job allocation 306853
Job ID 306853 connecting to c233, please wait...

[username@login01 ~]$ interactive -pgpu
salloc: Granted job allocation 306855
Job ID 306855 connecting to gpu02, please wait...