Andrew Cunningham |
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 _______________________________________________ Arpack-ng mailing list [hidden email] http://lists.scilab.org/mailman/listinfo/arpack-ng |
Sylvestre Ledru-4 |
On 16/11/2012 21:24, Andrew Cunningham wrote:
> 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'? release with this change ;) Sylvestre _______________________________________________ Arpack-ng mailing list [hidden email] http://lists.scilab.org/mailman/listinfo/arpack-ng |
Andrew Cunningham |
Hi,
Modifying ARPACK at that level is beyond me , I am afraid. I did find a workaround to my issue. I adjust the number of eigenvectors I extract such that I never ask for <8 Andrew
On Sat, Nov 17, 2012 at 7:18 AM, Sylvestre Ledru <[hidden email]> wrote: On 16/11/2012 21:24, Andrew Cunningham wrote: _______________________________________________ Arpack-ng mailing list [hidden email] http://lists.scilab.org/mailman/listinfo/arpack-ng |
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