dsyrfs man page on Scientific

```DSYRFS(1)		 LAPACK routine (version 3.2)		     DSYRFS(1)

NAME
DSYRFS - improves the computed solution to a system of linear equations
when the coefficient matrix is symmetric indefinite, and provides error
bounds and backward error estimates for the solution

SYNOPSIS
SUBROUTINE DSYRFS( UPLO,	 N,  NRHS,  A, LDA, AF, LDAF, IPIV, B, LDB, X,
LDX, FERR, BERR, WORK, IWORK, INFO )

CHARACTER	  UPLO

INTEGER	  INFO, LDA, LDAF, LDB, LDX, N, NRHS

INTEGER	  IPIV( * ), IWORK( * )

DOUBLE	  PRECISION A( LDA, * ), AF( LDAF, * ), B( LDB,	 *  ),
BERR( * ), FERR( * ), WORK( * ), X( LDX, * )

PURPOSE
DSYRFS  improves	 the computed solution to a system of linear equations
when the coefficient matrix is symmetric indefinite, and provides error
bounds and backward error estimates for the solution.

ARGUMENTS
UPLO    (input) CHARACTER*1
= 'U':  Upper triangle of A is stored;
= 'L':  Lower triangle of A is stored.

N       (input) INTEGER
The order of the matrix A.  N >= 0.

NRHS    (input) INTEGER
The  number of right hand sides, i.e., the number of columns of
the matrices B and X.  NRHS >= 0.

A       (input) DOUBLE PRECISION array, dimension (LDA,N)
The symmetric matrix A.	If UPLO	 =  'U',  the  leading	N-by-N
upper  triangular  part of A contains the upper triangular part
of the matrix A, and the strictly lower triangular part of A is
not referenced.	If UPLO = 'L', the leading N-by-N lower trian‐
gular part of A contains	 the  lower  triangular	 part  of  the
matrix  A,  and	the strictly upper triangular part of A is not
referenced.

LDA     (input) INTEGER
The leading dimension of the array A.  LDA >= max(1,N).

AF      (input) DOUBLE PRECISION array, dimension (LDAF,N)
The factored form of the matrix A.  AF contains the block diag‐
onal  matrix  D and the multipliers used to obtain the factor U
or L from the factorization A = U*D*U**T or  A  =  L*D*L**T  as
computed by DSYTRF.

LDAF    (input) INTEGER
The leading dimension of the array AF.  LDAF >= max(1,N).

IPIV    (input) INTEGER array, dimension (N)
Details	of  the	 interchanges  and the block structure of D as
determined by DSYTRF.

B       (input) DOUBLE PRECISION array, dimension (LDB,NRHS)
The right hand side matrix B.

LDB     (input) INTEGER
The leading dimension of the array B.  LDB >= max(1,N).

X       (input/output) DOUBLE PRECISION array, dimension (LDX,NRHS)
On entry, the solution matrix X, as  computed  by  DSYTRS.   On
exit, the improved solution matrix X.

LDX     (input) INTEGER
The leading dimension of the array X.  LDX >= max(1,N).

FERR    (output) DOUBLE PRECISION array, dimension (NRHS)
The estimated forward error bound for each solution vector X(j)
(the j-th column of the solution matrix X).  If	XTRUE  is  the
true  solution  corresponding  to X(j), FERR(j) is an estimated
upper bound for the magnitude of the largest element in (X(j) -
XTRUE) divided by the magnitude of the largest element in X(j).
The estimate is as reliable as the estimate for RCOND,  and  is
almost always a slight overestimate of the true error.

BERR    (output) DOUBLE PRECISION array, dimension (NRHS)
The componentwise relative backward error of each solution vec‐
tor X(j) (i.e., the smallest relative change in any element  of
A or B that makes X(j) an exact solution).

WORK    (workspace) DOUBLE PRECISION array, dimension (3*N)

IWORK   (workspace) INTEGER array, dimension (N)

INFO    (output) INTEGER
= 0:  successful exit
< 0:  if INFO = -i, the i-th argument had an illegal value

PARAMETERS
ITMAX is the maximum number of steps of iterative refinement.

LAPACK routine (version 3.2)	 November 2008			     DSYRFS(1)
```
[top]

List of man pages available for Scientific

Copyright (c) for man pages and the logo by the respective OS vendor.

For those who want to learn more, the polarhome community provides shell access and support.