# dlarra.f(3) [centos man page]

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.AuthorGenerated automatically by Doxygen for LAPACK from the source code.Version 3.4.2Tue Sep 25 2012 dlarra.f(3)

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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.AuthorGenerated automatically by Doxygen for LAPACK from the source code.Version 3.4.2Tue Sep 25 2012 dlarra.f(3)