Optimisation or minimisation is available in relax via the `minimise.grid_search` and `minimise.execute` user functions.
The mathematical model optimised depends on the current data pipe type - it is implemented differently for each specific analysis.
For analyses such as the steady state NOE (Chapter 6) or reduced spectral density mapping (Chapter 8), the solution can be found by direct calculation rather than optimisation.
In these cases, the `minimise.calculate` user function should be used instead.

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