#
User Interface

The basic user interface of MLD2P4 consists of eight methods. The six methods `init`, `set`, `build`, `hierarchy_build`, `smoothers_build` and `apply` encapsulate all the functionalities for the setup and the application of any multilevel and one-level preconditioner implemented in the package. The method `free` deallocates the preconditioner data structure, while `descr` prints a description of the preconditioner setup by the user. For backward compatibility, methods are also accessible as stand-alone subroutines.

For each method, the same user interface is overloaded with respect to the real/ complex case and the single/double precision; arguments with appropriate data types must be passed to the method, i.e.,

- the sparse matrix data structure, containing the matrix to be preconditioned, must be of type `psb_`x `spmat_type` with x = `s` for real single precision, x = `d` for real double precision, x = `c` for complex single precision, x = `z` for complex double precision;
- the preconditioner data structure must be of type `mld_`x `prec_type`, with x = `s`, `d`, `c`, `z`, according to the sparse matrix data structure;
- the arrays containing the vectors and involved in the preconditioner application must be of type `psb_`x `vect_type` with x = `s`, `d`, `c`, `z`, in a manner completely analogous to the sparse matrix type;
- real parameters defining the preconditioner must be declared according to the precision of the sparse matrix and preconditioner data structures (see Section 6.2).

A description of each method is given in the remainder of this section.

Subsections

- Method init
- Method set
- Method hierarchy_build
- Method smoothers_build
- Method build
- Method apply
- Method free
- Method descr
- Auxiliary Methods
  - Method: dump
  - Method: clone
  - Method: sizeof
  - Method: allocate_wrk
  - Method: free_wrk