AHMED TOUHAMI, Hassan 1st University, Morocco Given a regular matrix pencil λB − A and a positively oriented contour γ in the complex plane, the spectral dichotomy methods applied to λB − A and γ consist in determining whether λB − A possesses eigenvalues on or in a neighborhood of γ . When no such eigenvalues exist, these methods compute iteratively the spectral projector P onto the right deflating subspace of λB − A associated with the eigenvalues inside/outside γ . The computation of the projector is accompanied by the spectral norm H of a Hermitian positive definite matrix H called the dichotomy condition number, which indicates the numerical quality of the spectral projector P. The smaller H is, the better this quality. This article presents a MATLAB program (specdicho) implementing the main types of spectral dichotomy where γ is a circle, an ellipse, the imaginary axis or a parabola.
ACM Reference Format:Sadkane, M. and Touhami, A. 2012. Algorithm 918: specdicho: A MATLAB program for the spectral dichotomy of regular matrix pencils.