Modules

The module system is a program, running on most supercomputers, that simplifies using different software in a precise and controlled manner. Oftentimes a supercomputer has more software installed than the average user will ever use. Frequently there are also multiple version of the same program available at the same time, to enable backward compatibility. A prominent example of this are Compilers, which sometimes have the tendency to break older programs with new versions.

Usage

To get a list of all currently loaded modules, one can employ

$ module list

and might receive something like:

Currently Loaded Modulefiles:
1) DEVELOP                3) intelmpi/2017.4
2) intel/16.0             4) likwid/system-default

detailing that from the DEVELOP group the Intel Compiler ICC in version 16, the Intel implementation of MPI in Version 2017.4 and the system default version of Likwid are currently loaded and usable.

Calling

$ module avail

lists all available (loadable) modules and module groups. With the information of these two commands, one can select module to load/unload/switch with

$ module load/unload x

to load or unload module x or

$ module switch x y

to switch out module x for module y. Switching is especially useful, to switch to a different version of the same program.

If you recurrently need lots of modules, this loading can be automated with an sh-file, so that you just have to execute the file once and it loads all modules, you need.

Using these commands, the module system takes care to set all the system variables, so the desired applications are referenced and called correctly.