I'm attempting to do a convergence study on my basis, see how large my basis need to be to make my results accurate, does that help?
-Andrew On May 14, 2012, at 9:55 PM, Shri wrote: > What are you trying to do by removing the rows/columns of the matrix? Are > there any variables that you want to treat as constants and hence eliminating > the rows and columns? > > Shri > > On May 14, 2012, at 10:51 PM, Andrew Spott wrote: > >> Is there a computational cost to using a sparse matrix that is much bigger >> than it should be? >> >> for example, say you have a matrix that is n x n, but you only store >> anything in the first m rows and columns (m < n). >> >> Also, would you then have to redo the matrix distribution among nodes by >> hand, or will PETSC do it for you? >> >> Thanks for the quick reply >> >> -Andrew >> >> On May 14, 2012, at 9:38 PM, Jed Brown wrote: >> >>> On Mon, May 14, 2012 at 9:33 PM, Andrew Spott <andrew.spott at gmail.com> >>> wrote: >>> What is the best way to selectively add/remove columns/rows of a Mat? >>> >>> Is there a way to do it in place, or does it require essentially moving the >>> values to a new matrix? >>> >>> If you only need to add/remove a small number of values, it's best to >>> allocate for all that might be present and just store explicit zeros. >>> >>> To add or remove rows, you are also changing the vector size that can be >>> multiplied against, and the data structure must be rebuilt. This is why >>> it's frequently preferable to use MatZeroRows (or a variant) instead of >>> removing them from the data structure. >> > -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20120514/9d54f416/attachment.htm>
