The environment modules are a system that allows you to quickly and easily modify your shell environment to access different software packages. The HEC offers a large (and growing) number of software packages to users, and each package may contain several tools, manual pages and libraries, or may require special setup to work properly. Some software packages come in several versions or flavours, many of which conflict with each other. Modules allows you to tailor your shell to access exactly the versions of packages you need by setting up the relevant environment variables for you, and automatically avoiding many possible conflicts between packages.



More information

 Viewing available modules

To view the available modules, enter the following:

module avail


A typical output would look like this:

--------- /usr/shared_apps/Modules/compilers ---------
cuda/5.0 openmpi/1.6.5-gcc pgi/13.5
intel/13.0 openmpi/1.6.5-intel

--------- /usr/shared_apps/Modules/libraries ---------
fftw/3.3.3 gsl/1.16

----------- /usr/shared_apps/Modules/apps -----------
R/3.0.1 matlab/2013a stata/12 valgrind/3.8.1

For each available module, the name of the software package is listed first, followed by an optional "/" character and the version or flavour of the package offered. Where multiple versions or flavours of a package exist, the default version is indicated. The default version can be accessed using just the module name, rather than the full name.

A brief description of each software package can be obtained with the module whatis command:

wayland> module whatis matlab
matlab : The MATLAB numerical computing environment (2010b)

homepage: http://www.mathworks.com/


As the full list of modules is lengthy, you can type module avail packagename to list versions of the specified package name. For example:

wayland> module avail intel

--------- /usr/shared_apps/Modules/modulefiles ---------
intel/10.1 intel/11.1 intel/12.1(default)




 Using modules

To setup up your shell environment to access the required package, use the module add command. For example:

module add intel


The above command will configure your environment to use the current default version of the Intel Compiler Suite tools, which in the example output from "module avail" above would version 12.1. To request a specific version of a package (e.g. version 11.1), use the full module name:

module add intel/11.1


To view the modules currently added to your environment, use the module list command:

wayland> module list
Currently Loaded Modulefiles:
1) intel/11.1


To remove modules from your environment, use the module rm command:

wayland> module rm intel

wayland> module list
No Modulefiles Currently Loaded.




 Module conflicts

There are certain module combinations which may cause problems when both are present in your environment. Examples include cases where modules offer applications or libraries with identical names (which may cause confusion as to exactly which one is being used), or when an application is strongly dependent on a specific compiler and its libraries (in which case the module will itself set up access to the required compiler version)

In such cases, modules are designed to conflict. Attempting to load a module which conflicts with one already added to your environment will generate a warning message and the conflicting module will not be loaded. For example, compiler suites are set to conflict with each other so that you only ever have a single compiler and its associated libraries available in your environment at any one time:

wayland> module add intel
wayland> module add pgi
pgi/11.5(15):ERROR:150: Module 'pgi/11.5' conflicts with the currently loaded module(s) 'intel/12.1'
pgi/11.5(15):ERROR:102: Tcl command execution failed: conflict pgi intel


The first error line shows exactly which two modules generate the conflict. The second error message shows the general rule that triggered the warning message.

To resolve a conflict simply remove the currently loaded conflicting module before adding the new one.




 Customising your environment

Module instructions do not persist across sessions; if you log out and log back in again, no modules will be loaded in your new login session. If there are a core set of packages which you access regularly, you can place relevant module add commands into your shell startup scripts - either .login for tcsh or .profile for bash.




 Switching versions

Sometimes you may wish to switch between different versions of a software package. Rather than invoke module rm followed by module add, you can simply use module switch instead:

% module add pgi/6.2-64-bit

% module list
Currently Loaded Modulefiles:
1) pgi/6.2-64-bit

% module switch pgi/6.2-32-bit

% module list
Currently Loaded Modulefiles:
1) pgi/6.2-32-bit




 Environment setup

If you want to see what environment setup a module is doing behind the scenes, use module show. For example:

wayland> module show R/2.11.1
-----------------------------------------------
/usr/shared_apps/Modules/modulefiles/R/2.11.1:

module-whatis the R stats package version 2.11.1

homepage: http://cran.r-project.org/
conflict R
prepend-path PATH /usr/shared_apps/packages/R-2.11.1/bin
prepend-path LD_LIBRARY_PATH /usr/shared_apps/packages/R-2.11.1/lib64/R/lib


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