# DragonFly On-Line Manual Pages

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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
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)
```

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