DragonFly On-Line Manual Pages

Search: Section:  


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 Sat Nov 16 2013 dlarra.f(3)

Search: Section: