<html><head><meta http-equiv="content-type" content="text/html; charset=us-ascii"></head><body style="overflow-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;"><div><br></div> I have created an MR that documents this and moved the error checking to a more appropriate location <a href="https://gitlab.com/petsc/petsc/-/merge_requests/6070">https://gitlab.com/petsc/petsc/-/merge_requests/6070</a><div><br><div><div><br><blockquote type="cite"><div>On Feb 14, 2023, at 4:33 AM, Pierre Bernigaud <pierre.bernigaud@onera.fr> wrote:</div><br class="Apple-interchange-newline"><div><meta http-equiv="Content-Type" content="text/html; charset=UTF-8"><div style="font-size: 10pt; font-family: Verdana,Geneva,sans-serif"><p>Dear all, <br><br>I hope this email finds you well. <br>We are currently working on a solver which is employing DMDA with SNES. The jacobian is computed via FDColoring, ie: </p><p>call DMDACreate1D(PETSC_COMM_WORLD, DM_BOUNDARY_GHOSTED, NY, NC, NGc, PETSC_NULL_INTEGER, dmF, ierr)</p><p>! ----- Some steps ... </p><p>call DMCreateColoring(dmF, IS_COLORING_GLOBAL, iscoloring, ierr)<br>call MatFDColoringCreate(Jac,iscoloring, matfdcoloring, ierr)<br>call MatFDColoringSetFunction(matfdcoloring, FormFunction, CTX, ierr)<br>call MatFDColoringSetUp(Jac ,iscoloring,matfdcoloring, ierr)<br>call SNESSetJacobian(snes, Jac, Jac, SNESComputeJacobianDefaultColor, matfdcoloring, ierr)</p><p>Everything is running smoothly. <br><span style="font-size: 10pt;">Recently, we modified the boundary conditions such as to use periodic BC: </span></p><p>call DMDACreate1D(PETSC_COMM_WORLD, DM_BOUNDARY_PERIODIC, NY, NC, NGc, PETSC_NULL_INTEGER, dmF, ierr)</p><p>We then encountered frequent crashes when calling MatFDColoringSetUp, depending on the number of cells NY. After looking for an solution, I found this old thread: <a href="https://lists.mcs.anl.gov/pipermail/petsc-users/2013-May/017449.html">https://lists.mcs.anl.gov/pipermail/petsc-users/2013-May/017449.html</a> <br>It appears that when using periodic BC, FDColoring can only be used if the number of cells is divisible by 2*NGc+1. Even though this is only a slight annoyance, I was wondering if you were working on this matter / if you had a quick fix at hand? At any rate, I think it would be nice if a warning was displayed in the FDColoring documentation? <br><br>Respectfully, <br>Pierre Bernigaud </p>
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