dlaneg man page on Scientific

Man page or keyword search:  
man Server   26626 pages
apropos Keyword Search (all sections)
Output format
Scientific logo
[printable version]

DLANEG(1)	    LAPACK auxiliary routine (version 3.2)	     DLANEG(1)

NAME
       DLANEG  -  computes  the	 Sturm	count,	the  number of negative pivots
       encountered while factoring tridiagonal T - sigma I = L D L^T

SYNOPSIS
       FUNCTION DLANEG( N, D, LLD, SIGMA, PIVMIN, R )

	   IMPLICIT	NONE

	   INTEGER	DLANEG

	   INTEGER	N, R

	   DOUBLE	PRECISION PIVMIN, SIGMA

	   DOUBLE	PRECISION D( * ), LLD( * )

PURPOSE
       DLANEG computes the Sturm count, the number of negative pivots  encoun‐
       tered  while  factoring tridiagonal T - sigma I = L D L^T.  This imple‐
       mentation works directly on the factors without forming the tridiagonal
       matrix  T.  The Sturm count is also the number of eigenvalues of T less
       than sigma.
       This routine is called from DLARRB.
       The current routine does	 not  use  the	PIVMIN	parameter  but	rather
       requires	 IEEE-754  propagation	of  Infinities and NaNs.  This routine
       also has no input range restrictions but does require default exception
       handling	 such  that  x/0  produces Inf when x is non-zero, and Inf/Inf
       produces NaN.  For more information, see:
	 Marques, Riedy, and Voemel, "Benefits of IEEE-754 Features in
	 Modern Symmetric Tridiagonal Eigensolvers," SIAM Journal on
	 Scientific Computing, v28, n5, 2006.  DOI 10.1137/050641624
	 (Tech report version in LAWN 172 with the same title.)

ARGUMENTS
       N       (input) INTEGER
	       The order of the matrix.

       D       (input) DOUBLE PRECISION array, dimension (N)
	       The N diagonal elements of the diagonal matrix D.

       LLD     (input) DOUBLE PRECISION array, dimension (N-1)
	       The (N-1) elements L(i)*L(i)*D(i).

       SIGMA   (input) DOUBLE PRECISION
	       Shift amount in T - sigma I = L D L^T.

       PIVMIN  (input) DOUBLE PRECISION
	       The minimum pivot in the Sturm sequence.	 May be used when zero
	       pivots are encountered on non-IEEE-754 architectures.

       R       (input) INTEGER
	       The  twist index for the twisted factorization that is used for
	       the negcount.

FURTHER DETAILS
       Based on contributions by
	  Osni Marques, LBNL/NERSC, USA
	  Christof Voemel, University of California, Berkeley, USA
	  Jason Riedy, University of California, Berkeley, USA

 LAPACK auxiliary routine (versioNovember 2008			     DLANEG(1)
[top]

List of man pages available for Scientific

Copyright (c) for man pages and the logo by the respective OS vendor.

For those who want to learn more, the polarhome community provides shell access and support.

[legal] [privacy] [GNU] [policy] [cookies] [netiquette] [sponsors] [FAQ]
Tweet
Polarhome, production since 1999.
Member of Polarhome portal.
Based on Fawad Halim's script.
....................................................................
Vote for polarhome
Free Shell Accounts :: the biggest list on the net