
DPPCON(l) ) DPPCON(l)
NAME
DPPCON  estimate the reciprocal of the condition number (in the 1norm) of a real symmet
ric positive definite packed matrix using the Cholesky factorization A = U**T*U or A =
L*L**T computed by DPPTRF
SYNOPSIS
SUBROUTINE DPPCON( UPLO, N, AP, ANORM, RCOND, WORK, IWORK, INFO )
CHARACTER UPLO
INTEGER INFO, N
DOUBLE PRECISION ANORM, RCOND
INTEGER IWORK( * )
DOUBLE PRECISION AP( * ), WORK( * )
PURPOSE
DPPCON estimates the reciprocal of the condition number (in the 1norm) of a real symmet
ric 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))).
ARGUMENTS
UPLO (input) CHARACTER*1
= 'U': Upper triangle of A is stored;
= 'L': Lower triangle of A is stored.
N (input) INTEGER
The order of the matrix A. N >= 0.
AP (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 jth column of U or L is stored
in the array AP as follows: if UPLO = 'U', AP(i + (j1)*j/2) = U(i,j) for 1<=i<=j;
if UPLO = 'L', AP(i + (j1)*(2nj)/2) = L(i,j) for j<=i<=n.
ANORM (input) DOUBLE PRECISION
The 1norm (or infinitynorm) of the symmetric matrix A.
RCOND (output) DOUBLE PRECISION
The reciprocal of the condition number of the matrix A, computed as RCOND =
1/(ANORM * AINVNM), where AINVNM is an estimate of the 1norm of inv(A) computed
in this routine.
WORK (workspace) DOUBLE PRECISION array, dimension (3*N)
IWORK (workspace) INTEGER array, dimension (N)
INFO (output) INTEGER
= 0: successful exit
< 0: if INFO = i, the ith argument had an illegal value
LAPACK version 3.0 15 June 2000 DPPCON(l) 
