dlarra.f(3)							      LAPACK							       dlarra.f(3)

NAME

       dlarra.f -

SYNOPSIS

   Functions/Subroutines
       subroutine dlarra (N, D, E, E2, SPLTOL, TNRM, NSPLIT, ISPLIT, INFO)
	   DLARRA computes the splitting points with the specified threshold.

Function/Subroutine Documentation
   subroutine dlarra (integerN, double precision, dimension( * )D, double precision, dimension( * )E, double precision, dimension( * )E2, double
       precisionSPLTOL, double precisionTNRM, integerNSPLIT, integer, dimension( * )ISPLIT, integerINFO)
       DLARRA computes the splitting points with the specified threshold.

       Purpose:

	    Compute the splitting points with threshold SPLTOL.
	    DLARRA sets any "small" off-diagonal elements to zero.

       Parameters:
	   N

		     N is INTEGER
		     The order of the matrix. N > 0.

	   D

		     D is DOUBLE PRECISION array, dimension (N)
		     On entry, the N diagonal elements of the tridiagonal
		     matrix T.

	   E

		     E is DOUBLE PRECISION array, dimension (N)
		     On entry, the first (N-1) entries contain the subdiagonal
		     elements of the tridiagonal matrix T; E(N) need not be set.
		     On exit, the entries E( ISPLIT( I ) ), 1 <= I <= NSPLIT,
		     are set to zero, the other entries of E are untouched.

	   E2

		     E2 is DOUBLE PRECISION array, dimension (N)
		     On entry, the first (N-1) entries contain the SQUARES of the
		     subdiagonal elements of the tridiagonal matrix T;
		     E2(N) need not be set.
		     On exit, the entries E2( ISPLIT( I ) ),
		     1 <= I <= NSPLIT, have been set to zero

	   SPLTOL

		     SPLTOL is DOUBLE PRECISION
		     The threshold for splitting. Two criteria can be used:
		     SPLTOL<0 : criterion based on absolute off-diagonal value
		     SPLTOL>0 : criterion that preserves relative accuracy

	   TNRM

		     TNRM is DOUBLE PRECISION
		     The norm of the matrix.

	   NSPLIT

		     NSPLIT is INTEGER
		     The number of blocks T splits into. 1 <= NSPLIT <= N.

	   ISPLIT

		     ISPLIT is INTEGER array, dimension (N)
		     The splitting points, at which T breaks up into blocks.
		     The first block consists of rows/columns 1 to ISPLIT(1),
		     the second of rows/columns ISPLIT(1)+1 through ISPLIT(2),
		     etc., and the NSPLIT-th consists of rows/columns
		     ISPLIT(NSPLIT-1)+1 through ISPLIT(NSPLIT)=N.

	   INFO

		     INFO is INTEGER
		     = 0:  successful exit

       Author:
	   Univ. of Tennessee

	   Univ. of California Berkeley

	   Univ. of Colorado Denver

	   NAG Ltd.

       Date:
	   September 2012

       Contributors:
	   Beresford Parlett, University of California, Berkeley, USA
	    Jim Demmel, University of California, Berkeley, USA
	    Inderjit Dhillon, University of Texas, Austin, USA
	    Osni Marques, LBNL/NERSC, USA
	    Christof Voemel, University of California, Berkeley, USA

       Definition at line 136 of file dlarra.f.

Author
       Generated automatically by Doxygen for LAPACK from the source code.

Version 3.4.2							  Tue Sep 25 2012						       dlarra.f(3)