Contents
zgtcon - estimate the reciprocal of the condition number of
a complex tridiagonal matrix A using the LU factorization as
computed by CGTTRF
SUBROUTINE ZGTCON(NORM, N, LOW, DIAG, UP1, UP2, IPIVOT, ANORM, RCOND,
WORK, INFO)
CHARACTER * 1 NORM
DOUBLE COMPLEX LOW(*), DIAG(*), UP1(*), UP2(*), WORK(*)
INTEGER N, INFO
INTEGER IPIVOT(*)
DOUBLE PRECISION ANORM, RCOND
SUBROUTINE ZGTCON_64(NORM, N, LOW, DIAG, UP1, UP2, IPIVOT, ANORM,
RCOND, WORK, INFO)
CHARACTER * 1 NORM
DOUBLE COMPLEX LOW(*), DIAG(*), UP1(*), UP2(*), WORK(*)
INTEGER*8 N, INFO
INTEGER*8 IPIVOT(*)
DOUBLE PRECISION ANORM, RCOND
F95 INTERFACE
SUBROUTINE GTCON(NORM, [N], LOW, DIAG, UP1, UP2, IPIVOT, ANORM,
RCOND, [WORK], [INFO])
CHARACTER(LEN=1) :: NORM
COMPLEX(8), DIMENSION(:) :: LOW, DIAG, UP1, UP2, WORK
INTEGER :: N, INFO
INTEGER, DIMENSION(:) :: IPIVOT
REAL(8) :: ANORM, RCOND
SUBROUTINE GTCON_64(NORM, [N], LOW, DIAG, UP1, UP2, IPIVOT, ANORM,
RCOND, [WORK], [INFO])
CHARACTER(LEN=1) :: NORM
COMPLEX(8), DIMENSION(:) :: LOW, DIAG, UP1, UP2, WORK
INTEGER(8) :: N, INFO
INTEGER(8), DIMENSION(:) :: IPIVOT
REAL(8) :: ANORM, RCOND
C INTERFACE
#include <sunperf.h>
void zgtcon(char norm, int n, doublecomplex *low, doublecom-
plex *diag, doublecomplex *up1, doublecomplex
*up2, int *ipivot, double anorm, double *rcond,
int *info);
void zgtcon_64(char norm, long n, doublecomplex *low, doub-
lecomplex *diag, doublecomplex *up1, doublecomplex
*up2, long *ipivot, double anorm, double *rcond,
long *info);
zgtcon estimates the reciprocal of the condition number of a
complex tridiagonal matrix A using the LU factorization as
computed by CGTTRF.
An estimate is obtained for norm(inv(A)), and the reciprocal
of the condition number is computed as RCOND = 1 / (ANORM *
norm(inv(A))).
NORM (input)
Specifies whether the 1-norm condition number or
the infinity-norm condition number is required:
= '1' or 'O': 1-norm;
= 'I': Infinity-norm.
N (input) The order of the matrix A. N >= 0.
LOW (input)
The (n-1) multipliers that define the matrix L
from the LU factorization of A as computed by
CGTTRF.
DIAG (input)
The n diagonal elements of the upper triangular
matrix U from the LU factorization of A.
UP1 (input)
The (n-1) elements of the first superdiagonal of
U.
UP2 (input)
The (n-2) elements of the second superdiagonal of
U.
IPIVOT (input)
The pivot indices; for 1 <= i <= n, row i of the
matrix was interchanged with row IPIVOT(i).
IPIVOT(i) will always be either i or i+1;
IPIVOT(i) = i indicates a row interchange was not
required.
ANORM (input)
If NORM = '1' or 'O', the 1-norm of the original
matrix A. If NORM = 'I', the infinity-norm of the
original matrix A.
RCOND (output)
The reciprocal of the condition number of the
matrix A, computed as RCOND = 1/(ANORM * AINVNM),
where AINVNM is an estimate of the 1-norm of
inv(A) computed in this routine.
WORK (workspace)
dimension(2*N)
INFO (output)
= 0: successful exit
< 0: if INFO = -i, the i-th argument had an ille-
gal value