SUBROUTINE DTPCON( NORM, UPLO, DIAG, N, A, RCOND, WORK, WORK2, INFO) CHARACTER * 1 NORM, UPLO, DIAG INTEGER N, INFO INTEGER WORK2(*) DOUBLE PRECISION RCOND DOUBLE PRECISION A(*), WORK(*) SUBROUTINE DTPCON_64( NORM, UPLO, DIAG, N, A, RCOND, WORK, WORK2, * INFO) CHARACTER * 1 NORM, UPLO, DIAG INTEGER*8 N, INFO INTEGER*8 WORK2(*) DOUBLE PRECISION RCOND DOUBLE PRECISION A(*), WORK(*)
SUBROUTINE TPCON( NORM, UPLO, DIAG, N, A, RCOND, [WORK], [WORK2], * [INFO]) CHARACTER(LEN=1) :: NORM, UPLO, DIAG INTEGER :: N, INFO INTEGER, DIMENSION(:) :: WORK2 REAL(8) :: RCOND REAL(8), DIMENSION(:) :: A, WORK SUBROUTINE TPCON_64( NORM, UPLO, DIAG, N, A, RCOND, [WORK], [WORK2], * [INFO]) CHARACTER(LEN=1) :: NORM, UPLO, DIAG INTEGER(8) :: N, INFO INTEGER(8), DIMENSION(:) :: WORK2 REAL(8) :: RCOND REAL(8), DIMENSION(:) :: A, WORK
void dtpcon(char norm, char uplo, char diag, int n, double *a, double *rcond, int *info);
void dtpcon_64(char norm, char uplo, char diag, long n, double *a, 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)) ).