You can use the output of -ksp_view, which gives the matrix information. Matt
On Tue, Sep 15, 2009 at 2:01 PM, Bernardo Rocha <bernardosk at gmail.com>wrote: > Hi everyone, > > I need to know the number of nonzero element of the matrix in an > application using PETSc. How can I do it? What is the best way to do it? > > As far as I'm concerned with PETSc, running on a single processor, I'm > using the command line argument "-info" and then I get this information in > some line of the output that looks like this > > [0] MatAssemblyEnd_SeqAIJ(): Matrix size: 5100 X 5100; storage space: 92706 > unneeded,44994 used > > then I simply get the number of used entries. > > But when I have a large simulation, where the matrix does not fit into the > memory of one processor, I must use several processors. My question is how > to get the number of nonzero entries of the "global" matrix? I wrote a > simple python script to parse the output and sum the number of entries used > on each processor, but I found out that my calculations are wrong, I'm > having twice more nonzero elements (I tested against a tiny simulation on a > single processor). It seems that on the output I'm parsing I have two kinds > of informations about the entries used: > > [0] MatAssemblyEnd_SeqAIJ(): Matrix size: 5100 X 5100; storage space: 92706 > unneeded,44994 used > > [0] MatAssemblyEnd_SeqAIJ(): Matrix size: 5100 X 5100; storage space: 0 > unneeded,44994 used > > That is, one that the "unneeded" field has some value and another that this > field is zero. Then I decided to discard the information where the field > "unneeded" is zero and finally the results matched perfectly with a single > processor case. > > So, i would like to know (1) why do I have these lines with "0 unneeded" > and (2) if there is a more elegant way to measure this. > > That's all! > Best regards, > Bernardo M. R. > -- 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/20090915/efa60f54/attachment.htm>
