<html><head></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; ">Hi Jed,<div><br></div><div>I forgot to note that my matrix is *extremely* well structured, because I am working on a (non-uniform) Cartesian mesh. The matrix that I want to solve results from discretizing the Laplacian, so in 3D it consists basically of only 7 diagonals. Do you think the same conclusions hold with regard to preconditioners?</div><div>Furthermore, I get these messages:</div><div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; font: normal normal normal 13px/normal Courier; ">[1] Mat_CheckCompressedRow(): Found the ratio (num_zerorows 76032)/(num_localrows 82944) > 0.6. Use CompressedRow routines.</div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; font: normal normal normal 12px/normal Courier; min-height: 14px; "><br></div></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; font: normal normal normal 12px/normal Courier; min-height: 14px; ">Does Petsc give a hint here to use other routines, or does it indicate what it is doing?</div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; font: normal normal normal 12px/normal Courier; min-height: 14px; "><br></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; font: normal normal normal 12px/normal Courier; min-height: 14px; ">Ben</div><div><br><div><div>Op 10 sep 2010, om 10:38 heeft Jed Brown het volgende geschreven:</div><br class="Apple-interchange-newline"><blockquote type="cite"><div>On Fri, 10 Sep 2010 10:27:17 -0600, Benjamin Sanderse <<a href="mailto:B.Sanderse@cwi.nl">B.Sanderse@cwi.nl</a>> wrote:<br><blockquote type="cite">- Until now I have been using the 'two-shell' approach suggested by Barry for debugging purposes. This approach works fine, but in a later stage I would like to include the petsc execution command back in Matlab. I tried the following in Matlab:<br></blockquote><blockquote type="cite">system('petscmpiexec -n 2 ./petsc_poisson_par -viewer_socket_port 5600 &);<br></blockquote><blockquote type="cite"><br></blockquote><blockquote type="cite">unix('petscmpiexec -n 2 ./petsc_poisson_par -viewer_socket_port 5600 &);<br></blockquote><blockquote type="cite"><br></blockquote><blockquote type="cite">In both cases this doesn't work, while issuing the command in a separate shell works fine. Any ideas?<br></blockquote><br>Please provide the output, "doesn't work" is not much information.<br><br><blockquote type="cite">- I am using CG to solve a symmetric positive definite matrix. As preconditioner I normally use ICC (incomplete choleski), but apparently this is not implemented in parallel in Petsc. Suggestions on what to take as preconditioner?<br></blockquote><br>Start with block Jacobi + ICC (-pc_type bjacobi -sub_pc_type icc) or ASM<br>+ ICC (-pc_type asm -sub_pc_type icc).<br><br>Jed<br></div></blockquote></div><br></div></body></html>