SUBROUTINE DTRCON( NORM, UPLO, DIAG, N, A, LDA, RCOND, WORK, WORK2, * INFO) CHARACTER * 1 NORM, UPLO, DIAG INTEGER N, LDA, INFO INTEGER WORK2(*) DOUBLE PRECISION RCOND DOUBLE PRECISION A(LDA,*), WORK(*) SUBROUTINE DTRCON_64( NORM, UPLO, DIAG, N, A, LDA, RCOND, WORK, * WORK2, INFO) CHARACTER * 1 NORM, UPLO, DIAG INTEGER*8 N, LDA, INFO INTEGER*8 WORK2(*) DOUBLE PRECISION RCOND DOUBLE PRECISION A(LDA,*), WORK(*)
SUBROUTINE TRCON( NORM, UPLO, DIAG, N, A, [LDA], RCOND, [WORK], * [WORK2], [INFO]) CHARACTER(LEN=1) :: NORM, UPLO, DIAG INTEGER :: N, LDA, INFO INTEGER, DIMENSION(:) :: WORK2 REAL(8) :: RCOND REAL(8), DIMENSION(:) :: WORK REAL(8), DIMENSION(:,:) :: A SUBROUTINE TRCON_64( NORM, UPLO, DIAG, N, A, [LDA], RCOND, [WORK], * [WORK2], [INFO]) CHARACTER(LEN=1) :: NORM, UPLO, DIAG INTEGER(8) :: N, LDA, INFO INTEGER(8), DIMENSION(:) :: WORK2 REAL(8) :: RCOND REAL(8), DIMENSION(:) :: WORK REAL(8), DIMENSION(:,:) :: A
void dtrcon(char norm, char uplo, char diag, int n, double *a, int lda, double *rcond, int *info);
void dtrcon_64(char norm, char uplo, char diag, long n, double *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)) ).