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Even_Ira is a Matlab code to compute some eigenvalues and associated eigenvectors of large, sparse even eigenvalue problems.
Even_Ira is close to Matlabs built-in function eigs in term of purpose and syntax.
An eigenvalue problem M*x=lambda*N*x is called even, if M is a real symmetric matrix and N a real skew-symmetric matrix.
Eigenvalues of even problems appear in pairs (lambda, -lambda on the real or imaginary axis) and quadruples (lambda, -lambda, conj(lambda), -conj(lambda)). Pairs and quadruples are returned as a wohle.
Copyright (c) 2013 Volker Mehrmann, Valeria Simoncini, Christian Schroeder
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