SUBROUTINE ZTBCON( NORM, UPLO, DIAG, N, NDIAG, A, LDA, RCOND, WORK, * WORK2, INFO) CHARACTER * 1 NORM, UPLO, DIAG DOUBLE COMPLEX A(LDA,*), WORK(*) INTEGER N, NDIAG, LDA, INFO DOUBLE PRECISION RCOND DOUBLE PRECISION WORK2(*) SUBROUTINE ZTBCON_64( NORM, UPLO, DIAG, N, NDIAG, A, LDA, RCOND, * WORK, WORK2, INFO) CHARACTER * 1 NORM, UPLO, DIAG DOUBLE COMPLEX A(LDA,*), WORK(*) INTEGER*8 N, NDIAG, LDA, INFO DOUBLE PRECISION RCOND DOUBLE PRECISION WORK2(*)
SUBROUTINE TBCON( NORM, UPLO, DIAG, N, NDIAG, A, [LDA], RCOND, [WORK], * [WORK2], [INFO]) CHARACTER(LEN=1) :: NORM, UPLO, DIAG COMPLEX(8), DIMENSION(:) :: WORK COMPLEX(8), DIMENSION(:,:) :: A INTEGER :: N, NDIAG, LDA, INFO REAL(8) :: RCOND REAL(8), DIMENSION(:) :: WORK2 SUBROUTINE TBCON_64( NORM, UPLO, DIAG, N, NDIAG, A, [LDA], RCOND, * [WORK], [WORK2], [INFO]) CHARACTER(LEN=1) :: NORM, UPLO, DIAG COMPLEX(8), DIMENSION(:) :: WORK COMPLEX(8), DIMENSION(:,:) :: A INTEGER(8) :: N, NDIAG, LDA, INFO REAL(8) :: RCOND REAL(8), DIMENSION(:) :: WORK2
void ztbcon(char norm, char uplo, char diag, int n, int ndiag, doublecomplex *a, int lda, double *rcond, int *info);
void ztbcon_64(char norm, char uplo, char diag, long n, long ndiag, doublecomplex *a, long lda, double *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)) ).