On Mon, Nov 27, 2017 at 8:08 PM, Jed Brown <[email protected]> wrote:
> I don't know the answer to your question (Matt?), but do you really need > to reorder the entire mesh or would it be sufficient to label your > points with their original numbering? Maybe I am wrong, but I think it amounts to the same thing. If we are going to output things in parallel, we would need to communicate to he writing process, which this essentially does. I thought I responded, but what has to happen is that the SF for this reordering must be decimated to produce a subSF for the subDM. Its just not simple, so I have not had the free time to work it out. Matt > Blaise A Bourdin <[email protected]> writes: > > > Hi, > > I am fighting with natural ordering in DMplex with multi-fields / multi > components DM. > > I need to read / write files in a distribution-independent ordering. The > natural way to do so is to define the natural ordering as that of the file, > then call DMPlexGlobalToNaturalBegin/End before VecView: > > The pseudo code would be > > > > DMPlexCreateFromFile(PETSC_COMM_WORLD,ifilename,interpolate,&dmUAS); > > // create default section associated with a complicated layout of > multiple fields > > // (U,\alpha,\sigma) > > DMSetUseNatural(dmUAS,PETSC_TRUE); > > DMPlexDistribute(dmUAS,0,&migrationSF,&dmDist); > > > > DMGetGlobalVector(dmDist,&UAS); > > DMGetGlobalVector(dmDist,&UASNatural); > > DMPlexGlobalToNaturalBegin(dmDist,UAS,UASNatural); > > DMPlexGlobalToNaturalEnd(dmDist,UAS,UASNatural); > > // Do my I/O stuff using UASNatural > > > > If I try to do the same thing one field at a time, things break: > > Say that I get the subDM for the first field (U): > > > > DMCreateSubDM(dmDist,1,&fieldU,&ISU,&dmU); > > > > Then dmU->useNatural is PETSC_FALSE and I cannot compute dmU->sfnatural > using DMPlexCreateGlobalToNaturalSF since I do not have the “sequential” > version of dmU. > > > > What is the proper way to handle this situation? Creating sequential > subDMs and calling DMDistribute on each of them is ugly and possibly costly. > > > > Regards, > > > > Blaise > > > > -- > > Department of Mathematics and Center for Computation & Technology > > Louisiana State University, Baton Rouge, LA 70803, USA > > Tel. +1 (225) 578 1612, Fax +1 (225) 578 4276 http://www.math.lsu.edu/~ > bourdin > -- 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 https://www.cse.buffalo.edu/~knepley/ <http://www.caam.rice.edu/~mk51/>
