Nicing background jobs

Why?  Even though we share computing resources within AMO Theory, the group that owns the machine gets the higher priority.   Nicing a job refers to the Unix/linux command for running a job at a lower priority so that it uses a smaller fraction of the CPU. 

When running on machines that are on someone's desktop, you should nice your jobs to 19 to give their interactive session highest priority. Otherwise, they could be waiting a few minutes to type their next word!

The actual Unix/linux commands that you use are nice and renice.  Nice values range from 0 to 19 with 0 being the highest priority and 19 the lowest.  Simple uses will be described below --- use the man pages for more information.

The easiest way to check the nice value of your job is to use top.  The column NI (sometimes NICE) gives the nice values.  The command ps can also be used --- check the man pages for syntax.

To nice your job to 19 when you start it, type
> nice +19 command.x &
This can be combined with the usual redirection commands.

To renice a job that has already been started, you need to know its PID (Process ID).  The PID is a 5 digit number that you can find using top.  The command is
> renice +19 12345
where 12345 is the PID.