Running Interactive Sessions with Idev

The idev utility initiates an interactive session on one or more compute nodes so that you can issue commands and run code as if you were doing so on your personal machine. An interactive session is useful for development, as you can quickly compile, run, and validate code. Accessing a single compute node is accomplished by simply executing idev on any of the TACC systems.

Initiating an Interactive Session

To learn about the command line options available for idev, use idev -help.

login1$ idev -help
...
OPTION ARGUMENTS         DESCRIPTION
-A     account_name      sets account name (default: in .idevrc)
-m     minutes           sets time in minutes (default: 30)
-p     queue_name        sets queue to named queue (default: -p development)
-r     resource_name     sets hardware
-t     hh:mm:ss          sets time to hh:mm:ss (default: 00:30:00)
-help      [--help     ] displays (this) help message
-v         [--version  ] output version information and exit

Let’s go over some of the most useful idev command line options that can customize your interactive session:

To change the time limit to be lesser or greater than the default 30 minutes, users can use the -m command line option. For example, a user requesting an interactive session for an hour would use the command line option -m 60.

To change the account_name associated with the interactive session, users can use the -A command line option. This option is useful for when a user has multiple allocations they belong to. For example, if I have allocations on accounts TACC and Training, I can use -A to set the allocation I want to be used like so: -A TACC or -A Training.

To change the queue to be different than the default development queue, users can use the -p command line option. For example, if a user wants to launch an interactive session on one of Frontera GPU nodes, they would use the command line option -p rtx or -p rtx-dev. You can learn more about the different queues of Frontera here.

Note: For the scope of this section, we will be using the default development queue.

To start a thirty-minute interactive session on a compute node in the development queue with our EXAMPLE allocation:

login1$ idev -A EXAMPLE

If launch is successful, you will see output that includes the following excerpts:

...
-----------------------------------------------------------------
      Welcome to the Frontera Supercomputer
-----------------------------------------------------------------
...

-> After your idev job begins to run, a command prompt will appear,
-> and you can begin your interactive development session.
-> We will report the job status every 4 seconds: (PD=pending, R=running).

-> job status:  PD
-> job status:  R

-> Job is now running on masternode= c205-004...OK
...
c205-004[clx](633)$

Exercise

Let’s execute a Python code that determines the larger of two numbers. The code also includes a 3-second delay before finishing.

c205-004[clx](634)$ cdw
c205-004[clx](635)$ unzip firststeps.zip
c205-004[clx](636)$ cd Lab01
c205-004[clx](637)$ pwd
/work2/02555/lima/frontera/Lab01
c205-004[clx](638)$ ls
example.slurm  example_template.slurm  my_code.py

Load the appropriate modules, and run my_code.py.

c205-004[clx](639)$ module load python3
c205-004[clx](640)$ python3 my_code.py
The larger number of 51 and 20 is 51

You can check the files that were generated using ls, and see the contents of the file with cat.

c205-004[clx](641)$ ls
duration.txt  example.slurm  example_template.slurm  my_code.py
c205-004[clx](642)$ cat duration
Done in 3.009739637374878 seconds.

To exit an interactive session, you can use the command logout.

Attention

In case you didn’t donwload the code in the section Transferring Files, you can download by doing:

[frontera]$ cdw
[frontera]$ wget https://github.com/Ernesto-Lima/YourFirstStepsAtTACC/raw/master/docs/steps_at_tacc/files/firststeps.zip
[frontera]$ unzip firststeps.zip