Design philosophy

We have made the ParPre library to a large extent a `black-box' library in order to make it as easy to use as possible. This is apparent in the following:

• The user never has direct access to, the preconditioner data structure.
• Any method parameters are set by function calls. As a result, parameter lists are always short, and no unnecessary parameters are passed.
• Parameters have sensible default settings, so that, in the absence of user calls setting them, the method will still perform satisfactorily.

The design philosophy and mathematical background are covered in detail in a companion paper [3].