MATLAB: Do I receive an error when I use the EIGS function in MATLAB 7.0 (R14)

arpacklrMATLABprocesseupdinfo

I use the following code to load a sparse matrix and determine its eigenvalue with the largest real part:
load matlabmat;
eigs(O, 1, 'lr');
However, I receive the following error:
 ??? Error using ==> eigs>processEUPDinfo
 Error with ARPACK routine dneupd:
 dnaupd did not find any eigenvalues to sufficient accuracy.
 Error in ==> eigs at 369
 flag = processEUPDinfo(nargin<3);

Best Answer

This error occurs when the input matrix of the EIGS function has a very high condition number, which makes EIGS unable to converge to the default tolerance of EPS.
As a workaround, reduce the tolerance of EIGS using the following commands:
opts.tol = 1e-3; 
eigs(O, 1, 'lr', opts);
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