CHECON(3f)               LAPACK routine (version 3.1)               CHECON(3f)



NAME
       CHECON - the reciprocal of the condition number of a complex Hermitian
       matrix A using the factorization A = U*D*U**H or A = L*D*L**H computed
       by CHETRF

SYNOPSIS
       SUBROUTINE CHECON( UPLO, N, A, LDA, IPIV, ANORM, RCOND, WORK, INFO )

           CHARACTER      UPLO

           INTEGER        INFO, LDA, N

           REAL           ANORM, RCOND

           INTEGER        IPIV( * )

           COMPLEX        A( LDA, * ), WORK( * )

PURPOSE
       CHECON estimates the reciprocal of the condition number of a complex
       Hermitian matrix A using the factorization A = U*D*U**H or A = L*D*L**H
       computed by CHETRF.

       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
               Specifies whether the details of the factorization are stored
               as an upper or lower triangular matrix.  = 'U':  Upper
               triangular, form is A = U*D*U**H;
               = 'L':  Lower triangular, form is A = L*D*L**H.

       N       (input) INTEGER
               The order of the matrix A.  N >= 0.

       A       (input) COMPLEX array, dimension (LDA,N)
               The block diagonal matrix D and the multipliers used to obtain
               the factor U or L as computed by CHETRF.

       LDA     (input) INTEGER
               The leading dimension of the array A.  LDA >= max(1,N).

       IPIV    (input) INTEGER array, dimension (N)
               Details of the interchanges and the block structure of D as
               determined by CHETRF.

       ANORM   (input) REAL
               The 1-norm of the original matrix A.

       RCOND   (output) REAL
               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.

       WORK    (workspace) COMPLEX array, dimension (2*N)

       INFO    (output) INTEGER
               = 0:  successful exit
               < 0:  if INFO = -i, the i-th argument had an illegal value



 LAPACK routine (version 3.1)    November 2006                      CHECON(3f)
