SUBROUTINE STBCON( NORM, UPLO, DIAG, N, NDIAG, A, LDA, RCOND, WORK, * WORK2, INFO) CHARACTER * 1 NORM, UPLO, DIAG INTEGER N, NDIAG, LDA, INFO INTEGER WORK2(*) REAL RCOND REAL A(LDA,*), WORK(*) SUBROUTINE STBCON_64( NORM, UPLO, DIAG, N, NDIAG, A, LDA, RCOND, * WORK, WORK2, INFO) CHARACTER * 1 NORM, UPLO, DIAG INTEGER*8 N, NDIAG, LDA, INFO INTEGER*8 WORK2(*) REAL RCOND REAL A(LDA,*), WORK(*)
SUBROUTINE TBCON( NORM, UPLO, DIAG, N, NDIAG, A, [LDA], RCOND, [WORK], * [WORK2], [INFO]) CHARACTER(LEN=1) :: NORM, UPLO, DIAG INTEGER :: N, NDIAG, LDA, INFO INTEGER, DIMENSION(:) :: WORK2 REAL :: RCOND REAL, DIMENSION(:) :: WORK REAL, DIMENSION(:,:) :: A SUBROUTINE TBCON_64( NORM, UPLO, DIAG, N, NDIAG, A, [LDA], RCOND, * [WORK], [WORK2], [INFO]) CHARACTER(LEN=1) :: NORM, UPLO, DIAG INTEGER(8) :: N, NDIAG, LDA, INFO INTEGER(8), DIMENSION(:) :: WORK2 REAL :: RCOND REAL, DIMENSION(:) :: WORK REAL, DIMENSION(:,:) :: A
void stbcon(char norm, char uplo, char diag, int n, int ndiag, float *a, int lda, float *rcond, int *info);
void stbcon_64(char norm, char uplo, char diag, long n, long ndiag, float *a, long lda, float *rcond, long *info);
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)) ).