User Interface

The basic user interface of MLD2P4 consists of six routines. The four routines mld_ precinit, mld_precset, mld_precbld and mld_precaply encapsulate all the functionalities for the setup and the application of any one-level and multi-level preconditioner implemented in the package. The routine mld_precfree deallocates the preconditioner data structure, while mld_precdescr prints a description of the preconditioner setup by the user.

For each routine, 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 routine, i.e.

• the sparse matrix data structure, containing the matrix to be preconditioned, must be of type psb_xspmat_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_xprec_type, with x = s, d, c, z, according to the sparse matrix data structure;
• the arrays containing the vectors $v$ and $w$ involved in the preconditioner application $w=M^{-1}v$ must be of type psb_xvect_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 routine is given in the remainder of this section.