In Unix, how should I submit CPU-intensive jobs?

Several mechanisms are available for handling large jobs in Unix, including reducing the priority of a process, running a process in the background, and, on some systems, submitting batch jobs.

On this page:

• Batch jobs
• Changing a job's priority and running a job in the background

Batch jobs

For information about the at and batch commands, see In Unix, what are the at and batch commands, and how do I use them to submit non-interactive job requests?

For information about using LoadLeveler and Moab on Big Red at Indiana University, see Batch jobs on Big Red and Big Red at Indiana University.

Note: Big Red is scheduled to be retired from service in June 2013. Indiana University is replacing it with Big Red II, the fastest university-owned supercomputer in the nation, capable of performing one quadrillion floating-point operations per second (1 petaflop). Based on Cray XE/XK technology, Big Red II has 676 XK nodes (each containing one AMD "Interlagos" processor and one NVIDIA "Kepler" GPU) and 344 XE nodes (each containing two AMD "Abu Dhabi" processors). For more, see Big Red II at Indiana University.

For information about using TORQUE (also called PBS) on Quarry at IU, see What is TORQUE, and how do I use it to submit and manage jobs on distributed computing systems?

Note: Following a system-wide upgrade in December 2012, Quarry now runs Red Hat Enterprise Linux version 6 (RHEL 6) and uses the Modules package (instead of SoftEnv) for manipulating user environments. For more, see Information about the 2012 upgrade to Quarry at IU. If you encounter any problems or have questions, email the High Performance Systems group.

Changing a job's priority and running a job in the background

To immediately execute a process at a lower priority, use the nice command. For example, to run a program called a.out at lower priority, at the Unix shell prompt, enter:

To let the job run in the background (so you can keep working interactively), add an ampersand ( & ) to the end of the command line:

When the job is complete, you will see something similar to this:

For more on the nice command, see the manual (man) page, which you can access by entering:

For more information on how to work with background processes, see the man page for your shell (e.g., csh, tcsh, ksh, bash).

At Indiana University, for personal or departmental Linux or Unix systems support, see At IU, how do I get support for Linux or Unix?