<div dir="ltr"><br>Thanks Matthew, i have made some progress but i am still unsure on how to proceed to make the DMDAs work as intended, i will try to lay out what i am trying now:<div><br></div><div>I was able to port the interpolation into the DMDA model but it works only in serial runs, and it becomes unstable for more than one processor running,</div><div><br></div><div>What i do is roughly this:</div><div><ul><li style="margin-left:15px">Calculate density at a cell-centered DMDA object, using a local vector so i can access the ghost rows (indices -1 and max+1)</li><li style="margin-left:15px">Interpolate into a face-centered DMDA object for velocities, using also a local vector.</li></ul><div>Doing this i get the right results using the same interpolation i used for my non-petsc implementation of the model, as long as i use only one processor but the doubts i have are:</div></div><div><ul><li style="margin-left:15px">How to use the local vectors properly: Is operating on them the recommended course in this case? </li><li style="margin-left:15px">How can i access the ghost indices in the global vector so i can then communicate GlobalToLocal? would this be a better strategy?</li><li style="margin-left:15px">I feel is wrong to interpolate a cell-centered based vector into a face-centered based vector, using the indices of the latter, what strategy would work best in this case?</li></ul><div>I also tried opening a global vector with a different DA layout than the one created (opening global density on the velocities DMDA layout) and this introduced an error in the GlobalToLocal, LocalToLocal, LocalToGlobal communication, something didn't happen if i used the local versions of these vectors instead,</div></div><div><br></div><div>Thanks for your help,</div><div><br></div><div>Manuel </div><div class="gmail_quote"><div dir="ltr"><br></div><div dir="ltr"><div><br></div><div><br></div><div><br></div></div><br><div class="gmail_quote"><div dir="ltr">On Sat, Oct 6, 2018 at 4:45 AM Matthew Knepley <<a href="mailto:knepley@gmail.com" target="_blank">knepley@gmail.com</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr"><div dir="ltr"><div class="gmail_quote"><div dir="ltr">On Fri, Oct 5, 2018 at 6:49 PM Manuel Valera <<a href="mailto:mvalera-w@sdsu.edu" target="_blank">mvalera-w@sdsu.edu</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div dir="auto">Hello,<div dir="auto"><br></div><div dir="auto">I'm trying to do a simple variable interpolation, from a cell center to a face in a staggered grid, my model data management is done with DMDAs, with two different DMs one for each cell position, </div><div dir="auto"><br></div><div dir="auto">I already did this task on a fortran only version of the model using the 4 closest neighbors of the scalars (cell center) to be interpolated at the velocity site (cell face), i did it using a loop over the domain, somehow this easy task is not translating into the DMDA framework, </div></div></blockquote><div><br></div><div>Its not clear to me what problem you are having. We have done this before. For example, </div><div><br></div><div> <a href="https://www.mcs.anl.gov/petsc/petsc-current/src/snes/examples/tutorials/ex30.c.html" target="_blank">https://www.mcs.anl.gov/petsc/petsc-current/src/snes/examples/tutorials/ex30.c.html</a></div><div><br></div><div>I would note that the development version of PETSc now has DMStag which supports staggered grid discretizations directly.</div><div><br></div><div> Thanks,</div><div><br></div><div> Matt</div><div> </div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div dir="auto"><div dir="auto">I'm not sure what I'm doing wrong or not aware of a easier way Petsc may have for this task, if you could point out an easier strategy or an example I would be grateful, </div><div dir="auto"><br></div><div dir="auto">Thanks, </div><div dir="auto"><br></div><div dir="auto"><br></div><div dir="auto"><br></div><div dir="auto"><br></div></div>
</blockquote></div><br clear="all"><div><br></div>-- <br><div dir="ltr" class="m_-4086939011740966609m_8651859862473364093gmail_signature"><div dir="ltr"><div><div dir="ltr"><div><div dir="ltr"><div>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</div><div><br></div><div><a href="http://www.cse.buffalo.edu/~knepley/" target="_blank">https://www.cse.buffalo.edu/~knepley/</a><br></div></div></div></div></div></div></div></div></div>
</blockquote></div>
</div></div>