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dppcon

 NAME
      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

 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 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))).

 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 fac-
              torization A = U**T*U or A = L*L**T, packed column-
              wise in a linear array.  The j-th column of U or L
              is stored in the array AP as follows: if UPLO = 'U',
              AP(i + (j-1)*j/2) = U(i,j) for 1<=i<=j; if UPLO =
              'L', AP(i + (j-1)*(2n-j)/2) = L(i,j) for j<=i<=n.

      ANORM   (input) DOUBLE PRECISION
              The 1-norm (or infinity-norm) 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 1-norm of inv(A) com-
              puted 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 i-th argument had an illegal
              value