DTPTRI(l)		LAPACK routine (version	1.1)		    DTPTRI(l)

NAME
  DTPTRI - compute the inverse of a real upper or lower	triangular matrix A
  stored in packed format

SYNOPSIS

  SUBROUTINE DTPTRI( UPLO, DIAG, N, AP,	INFO )

      CHARACTER	     DIAG, UPLO

      INTEGER	     INFO, N

      DOUBLE	     PRECISION AP( * )

PURPOSE
  DTPTRI computes the inverse of a real	upper or lower triangular matrix A
  stored in packed format.

ARGUMENTS

  UPLO	  (input) CHARACTER*1
	  = 'U':  A is upper triangular;
	  = 'L':  A is lower triangular.

  DIAG	  (input) CHARACTER*1
	  = 'N':  A is non-unit	triangular;
	  = 'U':  A is unit triangular.

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

  AP	  (input/output) DOUBLE	PRECISION array, dimension (N*(N+1)/2)
	  On entry, the	upper or lower triangular matrix A, stored columnwise
	  in a linear array.  The j-th column of A is stored in	the array AP
	  as follows: if UPLO =	'U', AP((j-1)*j/2 + i) = A(i,j)	for 1<=i<=j;
	  if UPLO = 'L', AP((j-1)*(n-j)	+ j*(j+1)/2 + i-j) = A(i,j) for
	  j<=i<=n.  See	below for further details.  On exit, the (triangular)
	  inverse of the original matrix, in the same packed storage format.

  INFO	  (output) INTEGER
	  = 0:	successful exit
	  < 0:	if INFO	= -i, the i-th argument	had an illegal value
	  > 0:	if INFO	= i, A(i,i) is exactly zero.  The triangular matrix
	  is singular and its inverse can not be computed.

FURTHER	DETAILS
  A triangular matrix A	can be transferred to packed storage using one of the
  following program segments:

  UPLO = 'U':			   UPLO	= 'L':

	JC = 1				 JC = 1
	DO 2 J = 1, N			 DO 2 J	= 1, N
	   DO 1	I = 1, J		    DO 1 I = J,	N
	      AP(JC+I-1) = A(I,J)	       AP(JC+I-J) = A(I,J)
      1	   CONTINUE		       1    CONTINUE
	   JC =	JC + J			    JC = JC + N	- J + 1
      2	CONTINUE		       2 CONTINUE