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DLARRV(l)					)					DLARRV(l)

       DLARRV - compute the eigenvectors of the tridiagonal matrix T = L D L^T given L, D and the
       eigenvalues of L D L^T

			  IWORK, INFO )



	   INTEGER	  IBLOCK( * ), ISPLIT( * ), ISUPPZ( * ), IWORK( * )

	   DOUBLE	  PRECISION D( * ), GERSCH( * ), L( * ), W( * ), WORK( * ), Z( LDZ, * )

       DLARRV  computes the eigenvectors of the tridiagonal matrix T = L D L^T given L, D and the
       eigenvalues of L D L^T. The input eigenvalues should  have  high  relative  accuracy  with
       respect	to the entries of L and D. The desired accuracy of the output can be specified by
       the input parameter TOL.

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

       D       (input/output) DOUBLE PRECISION array, dimension (N)
	       On entry, the n diagonal elements of the diagonal matrix D.  On	exit,  D  may  be

       L       (input/output) DOUBLE PRECISION array, dimension (N-1)
	       On  entry,  the (n-1) subdiagonal elements of the unit bidiagonal matrix L in ele-
	       ments 1 to N-1 of L. L(N) need not be set. On exit, L is overwritten.

       ISPLIT  (input) INTEGER array, dimension (N)
	       The splitting points, at which T breaks up into submatrices.  The first	submatrix
	       consists  of  rows/columns  1 to ISPLIT( 1 ), the second of rows/columns ISPLIT( 1
	       )+1 through ISPLIT( 2 ), etc.

       TOL     (input) DOUBLE PRECISION
	       The absolute error tolerance for  the  eigenvalues/eigenvectors.   Errors  in  the
	       input  eigenvalues  must be bounded by TOL.  The eigenvectors output have residual
	       norms bounded by TOL, and the dot  products  between  different	eigenvectors  are
	       bounded by TOL. TOL must be at least N*EPS*|T|, where EPS is the machine precision
	       and |T| is the 1-norm of the tridiagonal matrix.

       M       (input) INTEGER
	       The total number of eigenvalues found.  0 <= M <= N.  If RANGE = 'A', M =  N,  and
	       if RANGE = 'I', M = IU-IL+1.

       W       (input) DOUBLE PRECISION array, dimension (N)
	       The first M elements of W contain the eigenvalues for which eigenvectors are to be
	       computed.  The eigenvalues should be grouped by split-off block and  ordered  from
	       smallest  to largest within the block ( The output array W from DLARRE is expected
	       here ).	Errors in W must be bounded by TOL (see above).

       IBLOCK  (input) INTEGER array, dimension (N)
	       The  submatrix  indices	associated  with  the  corresponding  eigenvalues  in  W;
	       IBLOCK(i)=1  if eigenvalue W(i) belongs to the first submatrix from the top, =2 if
	       W(i) belongs to the second submatrix, etc.

       Z       (output) DOUBLE PRECISION array, dimension (LDZ, max(1,M) )
	       If JOBZ = 'V', then if INFO = 0, the first M columns of Z contain the  orthonormal
	       eigenvectors  of  the matrix T corresponding to the selected eigenvalues, with the
	       i-th column of Z holding the eigenvector associated with W(i).	If  JOBZ  =  'N',
	       then  Z is not referenced.  Note: the user must ensure that at least max(1,M) col-
	       umns are supplied in the array Z; if RANGE = 'V', the exact  value  of  M  is  not
	       known in advance and an upper bound must be used.

       LDZ     (input) INTEGER
	       The  leading  dimension	of  the  array	Z.   LDZ  >= 1, and if JOBZ = 'V', LDZ >=

       ISUPPZ  (output) INTEGER ARRAY, dimension ( 2*max(1,M) )
	       The support of the eigenvectors in Z, i.e., the	indices  indicating  the  nonzero
	       elements  in  Z.  The i-th eigenvector is nonzero only in elements ISUPPZ( 2*i-1 )
	       through ISUPPZ( 2*i ).

       WORK    (workspace) DOUBLE PRECISION array, dimension (13*N)

       IWORK   (workspace) INTEGER array, dimension (6*N)

       INFO    (output) INTEGER
	       = 0:  successful exit
	       < 0:  if INFO = -i, the i-th argument had an illegal value
	       > 0:  if INFO = 1, internal error in DLARRB if INFO = 2, internal error in DSTEIN

       Based on contributions by
	  Inderjit Dhillon, IBM Almaden, USA
	  Osni Marques, LBNL/NERSC, USA

LAPACK version 3.0			   15 June 2000 				DLARRV(l)
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