Contrib packages are non-official Torch packages. They might be not stable yet, not working on all platforms, not documented. Anyways, they might be useful! So we created for that purpose an external repository gathering these contributions. If you want to use them, go in you Torch directory and checkout them with: 

cd torch
svn checkout https://torch5-contrib.svn.sourceforge.net/svnroot/torch5-contrib/trunk contrib
This will create a contrib directory containing all these packages. Note that the name must be contrib.

Torch configuration will detect this optional contrib directory. As each of these packages might not be stable yet, they do not compile by default. You must enable the variable WITH_CONTRIB_xxxx at CMake configuration time, where xxxx is the name the package of interest, to enable the compilation of xxxx. This is easily achieved by toggling the variable in CMake GUI. Refer to the CMake hints section for more details on CMake variables.