init -- Initialize a preconditioner

call prec%init(icontxt,ptype, info)

Type:

Asynchronous.

On Entry

icontxt

the communication context.
Scope:global.
Type:required.
Intent: in.
Specified as: an integer value.

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 follows⁴:

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.