dtbcon(3P) Sun Performance Library dtbcon(3P)NAMEdtbcon - estimate the reciprocal of the condition number of a triangu‐
lar band matrix A, in either the 1-norm or the infinity-norm
SYNOPSIS
SUBROUTINE DTBCON(NORM, UPLO, DIAG, N, KD, A, LDA, RCOND, WORK,
WORK2, INFO)
CHARACTER * 1 NORM, UPLO, DIAG
INTEGER N, KD, LDA, INFO
INTEGER WORK2(*)
DOUBLE PRECISION RCOND
DOUBLE PRECISION A(LDA,*), WORK(*)
SUBROUTINE DTBCON_64(NORM, UPLO, DIAG, N, KD, A, LDA, RCOND, WORK,
WORK2, INFO)
CHARACTER * 1 NORM, UPLO, DIAG
INTEGER*8 N, KD, LDA, INFO
INTEGER*8 WORK2(*)
DOUBLE PRECISION RCOND
DOUBLE PRECISION A(LDA,*), WORK(*)
F95 INTERFACE
SUBROUTINE TBCON(NORM, UPLO, DIAG, [N], KD, A, [LDA], RCOND, [WORK],
[WORK2], [INFO])
CHARACTER(LEN=1) :: NORM, UPLO, DIAG
INTEGER :: N, KD, LDA, INFO
INTEGER, DIMENSION(:) :: WORK2
REAL(8) :: RCOND
REAL(8), DIMENSION(:) :: WORK
REAL(8), DIMENSION(:,:) :: A
SUBROUTINE TBCON_64(NORM, UPLO, DIAG, [N], KD, A, [LDA], RCOND,
[WORK], [WORK2], [INFO])
CHARACTER(LEN=1) :: NORM, UPLO, DIAG
INTEGER(8) :: N, KD, LDA, INFO
INTEGER(8), DIMENSION(:) :: WORK2
REAL(8) :: RCOND
REAL(8), DIMENSION(:) :: WORK
REAL(8), DIMENSION(:,:) :: A
C INTERFACE
#include <sunperf.h>
void dtbcon(char norm, char uplo, char diag, int n, int kd, double *a,
int lda, double *rcond, int *info);
void dtbcon_64(char norm, char uplo, char diag, long n, long kd, double
*a, long lda, double *rcond, long *info);
PURPOSEdtbcon estimates the reciprocal of the condition number of a triangular
band matrix A, in either the 1-norm or the infinity-norm.
The norm of A is computed and an estimate is obtained for norm(inv(A)),
then the reciprocal of the condition number is computed as
RCOND = 1 / ( norm(A) * norm(inv(A)) ).
ARGUMENTS
NORM (input)
Specifies whether the 1-norm condition number or the infin‐
ity-norm condition number is required:
= '1' or 'O': 1-norm;
= 'I': Infinity-norm.
UPLO (input)
= 'U': A is upper triangular;
= 'L': A is lower triangular.
DIAG (input)
= 'N': A is non-unit triangular;
= 'U': A is unit triangular.
N (input) The order of the matrix A. N >= 0.
KD (input)
The number of superdiagonals or subdiagonals of the triangu‐
lar band matrix A. KD >= 0.
A (input) The upper or lower triangular band matrix A, stored in the
first kd+1 rows of the array. The j-th column of A is stored
in the j-th column of the array A as follows: if UPLO = 'U',
A(kd+1+i-j,j) = A(i,j) for max(1,j-kd)<=i<=j; if UPLO = 'L',
A(1+i-j,j) = A(i,j) for j<=i<=min(n,j+kd). If DIAG = 'U',
the diagonal elements of A are not referenced and are assumed
to be 1.
LDA (input)
The leading dimension of the array A. LDA >= KD+1.
RCOND (output)
The reciprocal of the condition number of the matrix A, com‐
puted as RCOND = 1/(norm(A) * norm(inv(A))).
WORK (workspace)
dimension(3*N)
WORK2 (workspace)
dimension(N)
INFO (output)
= 0: successful exit
< 0: if INFO = -i, the i-th argument had an illegal value
6 Mar 2009 dtbcon(3P)
