# DragonFly On-Line Manual Pages

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```BSpar_sym_solve(3)               BlockSolve95               BSpar_sym_solve(3)

NAME
BSpar_sym_solve - Solve a symmetric positive definite system of
equations using conjugate gradients preconditioned by one of several
preconditioners.  The rhs can be a block of vectors.  The user should
not call this function directly, but BSpar_solve().

INPUT PARAMETERS
BS     - the number of vectors in the RHS
A      - a sparse matrix
fact_A - the incomplete factored version of A, if any
comm_A - the communication structure for A
in_rhs - the contiguous block of vectors forming the rhs
pre_option
- the preconditioner to use
PRE_ICC: incomplete Cholesky factorization
PRE_ILU: incomplete LU factorization
PRE_SSOR: Successive over relaxation
PRE_BJACOBI: Block Jacobi
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
residual
- the final computed residual
guess  - if TRUE, then initialize out_x to 0, otherwise the program
assumes that out_x contains an initial guess
procinfo
- the usual processor stuff

OUTPUT PARAMETERS
out_x  - the contiguous block of vectors containing the solution

RETURNS
The number of iterations or a negative number indicating the number of
iterations prior to finding that the matrix (or preconditioner) is not
positive definite.

NOTES
The preconditioners must be computed prior to calling BSpar_isolve.

SYNOPSIS
int BSpar_sym_solve(int BS, BSpar_mat *A, BSpar_mat *fact_A, BScomm *comm_A,
FLOAT *in_rhs, FLOAT *out_x, int pre_option, FLOAT err_tol, int max_iter,
FLOAT *residual, int guess, BSprocinfo *procinfo)

LOCATION
BlockSolve95/src/BSpar_sym_solve.c

2/12/1996                BSpar_sym_solve(3)
```

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