next up previous contents
Next: psb_precbld Builds Up: Preconditioner routines Previous: Preconditioner routines   Contents

psb_precinit -- Initialize a preconditioner 

call psb_precinit(prec, ptype, info)

Type:
Asynchronous.
On Entry
ptype
the type of preconditioner. Scope: global
Type: required
Intent: in.
Specified as: a character string, see usage notes.
On Exit

prec
Scope: local
Type: required
Intent: inout.
Specified as: a preconditioner data structure precdatapsb_prec_type.
info
Scope: global
Type: required
Intent: out.
Error code: if no error, 0 is returned.
Notes Legal inputs to this subroutine are interpreted depending on the $ptype$ string as follows3:
NONE
No preconditioning, i.e. the preconditioner is just a copy operator.
DIAG
Diagonal scaling; each entry of the input vector is multiplied by the reciprocal of the sum of the absolute values of the coefficients in the corresponding row of matrix $A$;
BJAC
Precondition by a factorization of the block-diagonal of matrix $A$, where block boundaries are determined by the data allocation boundaries for each process; requires no communication. Only the incomplete factorization $ILU(0)$ is currently implemented.