The following packages need to be installed before using relax:

Version 2.5 or higher.
Version 1.6 or higher. This package is used for most of the numerical calculations within relax.
Version 0.7.1 or higher. This package is optional. It is required only for the frame order theory analyses.
Version 2.9 or higher. This package is also optional. It is required for the operation of the graphical user interface (GUI).
Version 1.2 or higher. This optional dependency is essential for running relax in MPI multi-processor mode.

Older versions of these packages may work, use them at your own risk. If, for older dependency versions, errors do occur please submit a bug report to the bug tracker at That way a solution may be created for the next relax release.

Note that only the official Python distribution from is supported. If you use the Enthought Python Distribution (EPD) or other non-official distributions you may encounter problems with the relax C modules, the graphical user interface, or other issues. These alternative distributions are to be used at your own risk. Any issues encountered will not be considered as relax bugs.

The relax user manual (PDF), created 2016-10-28.