DGTCON(l)		LAPACK routine (version	1.1)		    DGTCON(l)

NAME
  DGTCON - estimate the	reciprocal of the condition number of a	real tridiag-
  onal matrix A	using the LU factorization as computed by DGTTRF

SYNOPSIS

  SUBROUTINE DGTCON( NORM, N, DL, D, DU, DU2, IPIV, ANORM, RCOND, WORK,
		     IWORK, INFO )

      CHARACTER	     NORM

      INTEGER	     INFO, N

      DOUBLE	     PRECISION ANORM, RCOND

      INTEGER	     IPIV( * ),	IWORK( * )

      DOUBLE	     PRECISION D( * ), DL( * ),	DU( * ), DU2( *	), WORK( * )

PURPOSE
  DGTCON estimates the reciprocal of the condition number of a real tridiago-
  nal matrix A using the LU factorization as computed by DGTTRF.

  An estimate is obtained for norm(inv(A)), and	the reciprocal of the condi-
  tion number is computed as RCOND = 1 / (ANORM	* norm(inv(A))).

ARGUMENTS

  NORM	  (input) CHARACTER*1
	  Specifies whether the	1-norm condition number	or the infinity-norm
	  condition number is required:
	  = '1'	or 'O':	 1-norm;
	  = 'I':	 Infinity-norm.

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

  DL	  (input) DOUBLE PRECISION array, dimension (N-1)
	  The (n-1) multipliers	that define the	matrix L from the LU factori-
	  zation of A as computed by DGTTRF.

  D	  (input) DOUBLE PRECISION array, dimension (N)
	  The n	diagonal elements of the upper triangular matrix U from	the
	  LU factorization of A.

  DU	  (input) DOUBLE PRECISION array, dimension (N-1)
	  The (n-1) elements of	the first superdiagonal	of U.

  DU2	  (input) DOUBLE PRECISION array, dimension (N-2)
	  The (n-2) elements of	the second superdiagonal of U.

  IPIV	  (input) INTEGER array, dimension (N)
	  The pivot indices; for 1 <= i	<= n, row i of the matrix was inter-
	  changed with row IPIV(i).  IPIV(i) will always be either i or	i+1;
	  IPIV(i) = i indicates	a row interchange was not required.

  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 an estimate of the 1-
	  norm of inv(A) computed in this routine.

  WORK	  (workspace) DOUBLE PRECISION array, dimension	(2*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