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Thread Subject: problem on eigs

Subject: problem on eigs

From: utab

Date: 25 Jun, 2008 15:16:01

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Dear all,

I have a rather strange problem(probably sth easy that I am missing),
which I could not figure out. Basically, I am trying to solve an eigen
problem by using the eigs function. My system matrices are sparse and
their full size is 330X330. They are both symmetric matrices. The problem
is that if I supply the command

[v,d] = eigs(A,B,30,'SM')

to find the smallest 30 eigenvalues and the corresponding eigenvectors,
it works fine, however if I increase the number of roots, it is giving
some of the first eigenvalues as 0. For instance, I used 40 as the number
of roots, and it ended with 23 zeros for the first 23 eigenvalues. I
tried to read the help for the eigs but I could not fix this error.

Any help on the problem is appreciated.

Thanks and best regards,

Umut

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