Frank Löffler (

March 31, 2019


Simple tool for using a (configurable) nice level for all processes.


This thorn tries to renice all processes of Cactus to a given nice level.
To renice a process means to change its nice level after the start. The nice level is a way to control the priority of processes for cpu power. It is always a good idea to give cpu-intensive jobs (like Cactus runs) a low priority if you are using desktop machines, especially if other people are using them too.

The nice level has a range of 20 to 19. A higher number means less priority. Mostly, normal processes will get 0 and only the superuser (root) can use negative values. Also only root can lower the nice level of a process, so if you nice your Cactus Run to 19, you cannot renice it later to an lower nice-level. The nice level of single processes can be controled by the system commands nice and/or renice. In the case of Cactus and Lamd this is not possible at startup. Therefore this thorn will set the nice level of your processes at CCTK_PARAMCHECK (in the beginning of the calculation).
This thorn has only one parameter: