On Tue, Oct 27, 2009 at 10:12 AM, francois pacull <span dir="ltr"><<a href="mailto:fpacull@fluorem.com">fpacull@fluorem.com</a>></span> wrote:<br><div class="gmail_quote"><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
Dear PETSc team,<br>
<br>
I have a few questions... During the resolution of a linear system in parallel, I am trying to apply a local LU solver to each of the SEQaij diagonal blocks of a MPIaij matrix partitioned with PARMETIS.<br>
<br>
- I started with MUMPS but it seems that it only works with unpartitioned aij matrices, is it really the case? Or could we use MUMPS to build an additive Schwarz preconditioner for example?<br></blockquote><div><br>You can use MUMPS for the subproblem solver.<br>
</div><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
- Then I tried UMFPACK. This works fine when the diagonal blocks (and the memory required to store the factors) are small but crashes when they are a little bit larger. For example with a "numeric final size" of 4203.7 MBytes, I got the following message "ERROR: out of memory" while there was plenty of memory left in the computer. I tried either with the UMFPACK version 5.2, downloaded by PETSc, or with a manually installed version 5.4, linked to PETSc. Is this a behavior from UMFPACK that you already experienced?<br>
</blockquote><div><br>Send all the error output. However, in oder to address more than 4G, you will need 64-bit pointers.<br><br></div><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
- Since UMFPACK seemed to have a memory limit around 4096 MB, I tried to install a PETSc version with the option "--with-64-bit-indices", however none of the partitioning packages could be compiled with this option (parmetis,chaco,jostle,party,scotch). Is there a way to compile PETSc with 64 bit indices AND a partitioning package?<br>
</blockquote><div><br>Not that I know of.<br> </div><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
- Finally, I tried to modify the PETSc source code umfpack.c so that it would deal with 64 bit indices, but I only ended up so far with a segmentation violation message at the execution... Is it the only way I could use UMPACK with large sparse matrices?<br>
</blockquote><div><br>Why not just upgrade to a 64-bit OS if you want to address so much memory on a single machine?<br><br> Matt<br> </div><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
Thank you,<br>
Regards,<br><font color="#888888">
francois pacull.<br>
</font></blockquote></div><br><br clear="all"><br>-- <br>What most experimenters take for granted before they begin their experiments is infinitely more interesting than any results to which their experiments lead.<br>-- Norbert Wiener<br>