Contents
dppcon - estimate the reciprocal of the condition number (in
the 1-norm) of a real symmetric positive definite packed
matrix using the Cholesky factorization A = U**T*U or A =
L*L**T computed by DPPTRF
SUBROUTINE DPPCON(UPLO, N, A, ANORM, RCOND, WORK, WORK2, INFO)
CHARACTER * 1 UPLO
INTEGER N, INFO
INTEGER WORK2(*)
DOUBLE PRECISION ANORM, RCOND
DOUBLE PRECISION A(*), WORK(*)
SUBROUTINE DPPCON_64(UPLO, N, A, ANORM, RCOND, WORK, WORK2, INFO)
CHARACTER * 1 UPLO
INTEGER*8 N, INFO
INTEGER*8 WORK2(*)
DOUBLE PRECISION ANORM, RCOND
DOUBLE PRECISION A(*), WORK(*)
F95 INTERFACE
SUBROUTINE PPCON(UPLO, [N], A, ANORM, RCOND, [WORK], [WORK2], [INFO])
CHARACTER(LEN=1) :: UPLO
INTEGER :: N, INFO
INTEGER, DIMENSION(:) :: WORK2
REAL(8) :: ANORM, RCOND
REAL(8), DIMENSION(:) :: A, WORK
SUBROUTINE PPCON_64(UPLO, [N], A, ANORM, RCOND, [WORK], [WORK2], [INFO])
CHARACTER(LEN=1) :: UPLO
INTEGER(8) :: N, INFO
INTEGER(8), DIMENSION(:) :: WORK2
REAL(8) :: ANORM, RCOND
REAL(8), DIMENSION(:) :: A, WORK
C INTERFACE
#include <sunperf.h>
void dppcon(char uplo, int n, double *a, double anorm, dou-
ble *rcond, int *info);
void dppcon_64(char uplo, long n, double *a, double anorm,
double *rcond, long *info);
dppcon estimates the reciprocal of the condition number (in
the 1-norm) of a real symmetric positive definite packed
matrix using the Cholesky factorization A = U**T*U or A =
L*L**T computed by DPPTRF.
An estimate is obtained for norm(inv(A)), and the reciprocal
of the condition number is computed as RCOND = 1 / (ANORM *
norm(inv(A))).
UPLO (input)
= 'U': Upper triangle of A is stored;
= 'L': Lower triangle of A is stored.
N (input) The order of the matrix A. N >= 0.
A (input) DOUBLE PRECISION array, dimension (N*(N+1)/2)
The triangular factor U or L from the Cholesky
factorization A = U**T*U or A = L*L**T, packed
columnwise in a linear array. The j-th column of
U or L is stored in the array A as follows: if
UPLO = 'U', A(i + (j-1)*j/2) = U(i,j) for 1<=i<=j;
if UPLO = 'L', A(i + (j-1)*(2n-j)/2) = L(i,j) for
j<=i<=n.
ANORM (input)
The 1-norm (or infinity-norm) of the symmetric
matrix A.
RCOND (output)
The reciprocal of the condition number of the
matrix A, computed as RCOND = 1/(ANORM * AINVNM),
where AINVNM is an estimate of the 1-norm of
inv(A) computed in this routine.
DOUBLE PRECISION array, WORK (workspace)
dimension(3*N)
WORK2 (workspace)
INTEGER array, dimension(N)
INFO (output)
= 0: successful exit
< 0: if INFO = -i, the i-th argument had an ille-
gal value