DPTTRF(l)		LAPACK routine (version	1.1)		    DPTTRF(l)

NAME
  DPTTRF - compute the factorization of	a real symmetric positive definite
  tridiagonal matrix A

SYNOPSIS

  SUBROUTINE DPTTRF( N,	D, E, INFO )

      INTEGER	     INFO, N

      DOUBLE	     PRECISION D( * ), E( * )

PURPOSE
  DPTTRF computes the factorization of a real symmetric	positive definite
  tridiagonal matrix A.

  If the subdiagonal elements of A are supplied	in the array E,	the factori-
  zation has the form A	= L*D*L**T, where D is diagonal	and L is unit lower
  bidiagonal; if the superdiagonal elements of A are supplied, it has the
  form A = U**T*D*U, where U is	unit upper bidiagonal.	(The two forms are
  equivalent if	A is real.)

ARGUMENTS

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

  D	  (input/output) DOUBLE	PRECISION array, dimension (N)
	  On entry, the	n diagonal elements of the tridiagonal matrix A.  On
	  exit,	the n diagonal elements	of the diagonal	matrix D from the
	  L*D*L**T factorization of A.

  E	  (input/output) DOUBLE	PRECISION array, dimension (N-1)
	  On entry, the	(n-1) off-diagonal elements of the tridiagonal matrix
	  A.  On exit, the (n-1) off-diagonal elements of the unit bidiagonal
	  factor L or U	from the factorization of A.

  INFO	  (output) INTEGER
	  = 0:	successful exit
	  < 0:	if INFO	= -i, the i-th argument	had an illegal value
	  > 0:	if INFO	= i, the leading minor of order	i is not positive
	  definite; if i < N, the factorization	could not be completed,	while
	  if i = N, the	factorization was completed, but D(N) =	0.