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BSpar_isolve(3)                  BlockSolve95                  BSpar_isolve(3)

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

                                   4/4/1996                    BSpar_isolve(3)