NAME

BSpar_isolve - Solve a symmetric indefinite system of equations using symmlq preconditioned by one of several preconditioners.

INPUT PARAMETERS

A

- a sparse matrix

fact_A

- the incomplete factored version of A, if any (NULL if not exist)

comm_A

- the communication structure for A

B

- a sparse matrix

comm_B

- the communication structure for B

in_rhs

- the rhs

shift

- the shift to multiply B by

pre_option

- the preconditioner to use
PRE_ICC: incomplete Cholesky factorization of A
PRE_ILU: incomplete LU factorization of A
PRE_SSOR: Successive over relaxation (using just A)
PRE_BJACOBI: Block Jacobi (using just A)

residual

- the final computed residual

procinfo

- the usual processor stuff

OUTPUT PARAMETERS

out_x

- the solution vector

RETURNS

The number of iterations.

NOTES

The system solved is (A-shift*B)out_x = in_rhs. The preconditioners must be computed prior to calling BSpar_isolve. For more information on the preconditioners, see the manual.

The following are now specified in the context:
err_tol - the tolerance to which to solve the problem
stop if the estimated norm of the residual divided by
the norm of the rhs is less than err_tol
max_iter - the maximum number of iterations to take
guess - if TRUE, then initialize out_x to 0, otherwise
the program assumes that out_x contains an initial
guess

SYNOPSIS

int BSpar_isolve(BSpar_mat *A, BSpar_mat *fact_A, BScomm *comm_A,


 BSpar_mat *B, BScomm *comm_B, FLOAT *in_rhs, FLOAT *out_x,


 FLOAT shift, FLOAT *residual, BSprocinfo *procinfo)

LOCATION

BlockSolve95/src/BSpar_isolve.c