.TH BSpar_isolve 3 "4/4/1996" " " "BlockSolve95"
.SH NAME
BSpar_isolve \- Solve a symmetric indefinite system of equations
using symmlq preconditioned by one of several
preconditioners.

.SH INPUT PARAMETERS
.PD 0
.TP
.B A 
- a sparse matrix
.PD 1
.PD 0
.TP
.B fact_A 
- the incomplete factored version of A, if any (NULL if not exist)
.PD 1
.PD 0
.TP
.B comm_A 
- the communication structure for A
.PD 1
.PD 0
.TP
.B B 
- a sparse matrix 
.PD 1
.PD 0
.TP
.B comm_B 
- the communication structure for B
.PD 1
.PD 0
.TP
.B in_rhs 
- the rhs
.PD 1
.PD 0
.TP
.B shift 
- the shift to multiply B by
.PD 1
.PD 0
.TP
.B pre_option 
- the preconditioner to use
.PD 1
.br
    PRE_ICC: incomplete Cholesky factorization of A
.br
    PRE_ILU: incomplete LU factorization of A
.br
    PRE_SSOR: Successive over relaxation (using just A)
.br
    PRE_BJACOBI: Block Jacobi (using just A)
.PD 0
.TP
.B residual 
- the final computed residual
.PD 1
.PD 0
.TP
.B procinfo 
- the usual processor stuff
.PD 1

.SH OUTPUT PARAMETERS
.PD 0
.TP
.B out_x 
- the solution vector
.PD 1

.SH RETURNS
The number of iterations.

.SH 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.

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

.SH SYNOPSIS
.nf
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)

.fi

.SH LOCATION
 BlockSolve95/src/BSpar_isolve.c