I'm using ARPACK to find the eigenvalues of a matrix, it works for some of the problems I need it for, but for others, it returns INFO = 3, which means:(adsbygoogle = window.adsbygoogle || []).push({});

Remark 4 says: No shifts could be applied during a cycle of the implicitly restarted Arnoldi iteration. One possibility is to increase the size of NCV relative to NEV. See remark 4 below.

I have tried increasing NCV, and playing with the values of both NEV and NCV, but no luck. At present there is no a-priori analysis to guide the selection of NCV relative to NEV. The only formal requrement is that NCV > NEV. However, it is recommended that NCV .ge. 2*NEV. If many problems of the same type are to be solved, one should experiment with increasing NCV while keeping NEV fixed for a given test problem. This will usually decrease the required number of OP*x operations but it also increases the work and storage required to maintain the orthogonal basis vectors. The optimal "cross-over" with respect to CPU time is problem dependent and must be determined empirically.

Anyone who has worked with ARPACK, and knows how to solve this problem, your help would be greatly appreciated.

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# ARPACK help

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