If you running a task (i.e., Synopsys Design Compiler) that requires more than 20 minutes of cpu time, you will need to change your cpu time limit from it's default of 20 minutes (1200 seconds).

A temporary cpu time limit change may be made by typing at the shell,
cpulimit (time in seconds)
i.e, to change the time limit to 10 hours, (36000 seconds), type,
cpulimit  36000

To unlimit the time limit, type
at the unix shell prompt in the xterm window that you will invoke the task or program to run.