DPTCON(l)		LAPACK routine (version	1.1)		    DPTCON(l)

NAME
  DPTCON - compute the reciprocal of the condition number (in the 1-norm) of
  a real symmetric positive definite tridiagonal matrix	using the factoriza-
  tion A = L*D*L**T or A = U**T*D*U computed by	DPTTRF

SYNOPSIS

  SUBROUTINE DPTCON( N,	D, E, ANORM, RCOND, WORK, INFO )

      INTEGER	     INFO, N

      DOUBLE	     PRECISION ANORM, RCOND

      DOUBLE	     PRECISION D( * ), E( * ), WORK( * )

PURPOSE
  DPTCON computes the reciprocal of the	condition number (in the 1-norm) of a
  real symmetric positive definite tridiagonal matrix using the	factorization
  A = L*D*L**T or A = U**T*D*U computed	by DPTTRF.

  Norm(inv(A)) is computed by a	direct method, and the reciprocal of the con-
  dition number	is computed as
	       RCOND = 1 / (ANORM * norm(inv(A))).

ARGUMENTS

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

  D	  (input) DOUBLE PRECISION array, dimension (N)
	  The n	diagonal elements of the diagonal matrix D from	the factori-
	  zation of A, as computed by DPTTRF.

  E	  (input) DOUBLE PRECISION array, dimension (N-1)
	  The (n-1) off-diagonal elements of the unit bidiagonal factor	U or
	  L from the factorization of A,  as computed by DPTTRF.

  ANORM	  (input) DOUBLE PRECISION
	  The 1-norm of	the original 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 the 1-norm of inv(A)
	  computed in this routine.

  WORK	  (workspace) DOUBLE PRECISION array, dimension	(N)

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

FURTHER	DETAILS
  The method used is described in Nicholas J. Higham, "Efficient Algorithms
  for Computing	the Condition Number of	a Tridiagonal Matrix", SIAM J. Sci.
  Stat.	Comput., Vol. 7, No. 1,	January	1986.