Firstly, thanks to everyone involved in maintaining ARPACK.

Maybe someone can help me with my problem. I am solving the classic 'vibration' problem in shift and invert mode (DSAUPD/DSEUPD).

In many cases, although I can store as many eigenvalues as I could extract by writing them to disk, I do not have sufficient memory to extract them all in one operation.

Since sadly the option HOWMNY= 'S' for DSEUPD is not implemented, I break the problem up into smaller chunks by moving the shift value around and so extract a smaller numbers of eigenvectors - that is, I actually solve the whole problem multiple times until I have all the eigenvectors I need..

This works great...except in an extreme case where I ask for one or two eigenvalues. Then ARPACK exceeds the number of allowed iterations. This seems odd, as if I take a case where I can extract 32 eigenvalues/vectors, then as a test, only ask for 2, the iterations are exceeded. Would anyone have an idea why this is happening?

BTW, Is anyone wokring on implementing the option HOWMNY= 'S'?

Thanks

Andrew

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