User function interface
In its simplest form, a user function is exactly the same as any other mathematical function: it takes a set of arguments (constants or values of variables) and returns a value as its result. In this form, which is the usual implementation, the function needs no information apart from the values of its arguments. It is possible to create more complicated functions which do use external data in some form.
Xpress NonLinear distinguishes six different types of user functions.
- A user function is called a map, if it takes and returns a single value.
- A user function is called a mapvec, if it takes an array of inputs, and returns a single evaluation value.
- A user function is called a multimap, if it takes an array of inputs, and also returns an array of evaluation values.
- A mapdelta user function is an extended version of a map that also returns its own partial derivatives when requested
- A mapvecdelta user function is an extended version of a mapvec that also returns its own partial derivatives when requested
- A multimapdelta user function is an extended version of a multimap that also returns its own partial derivatives when requested
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