Actually, it's quite sparse. In the 3600x3600 there are only just 4 nonzero entries in each row. This means it's 99.9% empty. My smaller 6x6 example is dense, but it's only practice building and manipulating matrices.
Respectfully, Adam On Tue, Jun 28, 2011 at 5:55 PM, Matthew Knepley <knepley at gmail.com> wrote: > It sounds like you have a dense matrix (from your example). Is this true? > If so, you should use Elemental (on Google Code). > > Thanks, > > Matt > > On Tue, Jun 28, 2011 at 8:55 AM, Adam Byrd <adam1.byrd at gmail.com> wrote: > >> Hi, >> >> I'm rather new to PETSc and trying to work out the best way to create and >> fill a large sparse matrix distributed over many processors. Currently, my >> goal is to create a 3600x3600 matrix in units of 12x12 blocks with several >> blocks on any given node. I'd like to create the matrix in such a way that >> each node only holds the information in it's handful of blocks and not the >> entire matrix. Eventually, this matrix is to be inverted (I know, inversion >> should be avoided, but as this is a Hamiltonian matrix from which I need the >> Green's function, I'm unaware of a way to forgo carrying out the inversion). >> Additionally, the values will be changed slightly and the matrix will be >> repeatedly inverted. It's structure will remain the same. In order to learn >> how to do this is I am starting with a small 6x6 matrix broken into four 3x3 >> blocks and distributed one block per node. I've been able to create a local >> 3x3 matrix on each node, with it's own values, and with the global >> row/column IDs correctly set to [0, 1, 2] or [3, 4, 5] depending on where >> the block is in the matrix. My problem manifests when I try to create the >> larger matrix from the individual smaller ones. When the matrix is >> constructed I'm trying to use MatSetValues and having each node pass in it's >> 3x3 block. I end up with an error that the sum of local lengths 12x12 does >> not match the global length 6x6. It appears as though this is from passing >> in four 3x3s and the program interpreting that as a 12x12 instead of as a >> 6x6 with the blocks in a grid. >> >> My question is then: is it possible to fill a matrix as a grid of blocks, >> or can I only fill it in groups of rows or columns? Also, am I approaching >> this problem the correct way, or are there more efficient ways of building >> this matrix with the ultimate goal of inverting it? >> >> I have included my copy of a modified example if it helps. I do apologize >> if this is answered somewhere in the documentation, I have been unable to >> find a solution. >> >> Respectfully, >> Adam >> > > > > -- > What most experimenters take for granted before they begin their > experiments is infinitely more interesting than any results to which their > experiments lead. > -- Norbert Wiener > -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20110628/967a1532/attachment.htm>
