Re: [petsc-users] Question on DMPlexCreateFromCellList and DMPlexCreateFromFile

[Danyang Su]

On 18-02-16 10:13 AM, Matthew Knepley wrote:
On Fri, Feb 16, 2018 at 11:36 AM, Danyang Su <danyang...@gmail.com 
<mailto:danyang...@gmail.com>> wrote:

    On 18-02-15 05:57 PM, Matthew Knepley wrote:

    On Thu, Feb 15, 2018 at 7:40 PM, Danyang Su <danyang...@gmail.com
    <mailto:danyang...@gmail.com>> wrote:

        Hi Matt,

        I have a question on DMPlexCreateFromCellList and
        DMPlexCreateFromFile. When use DMPlexCreateFromFile with Gmsh
        file input, it works fine and each processor gets its own
        part. However, when use DMPlexCreateFromCellList, all the
        processors have the same global mesh. To my understand, I
        should put the global mesh as input, right?


    No. Each process should get part of the mesh in
    CreateFromCellList(), but the most common thing to do is to
    feed the whole mesh in on proc 0, and nothing in on the other procs.
    Thanks for the explanation. It works now.


Great. Also feel free to suggest improvements, examples, or better 
documentation.
Thanks, I will bother you a lot recently while porting the code from 
structured grid version to unstructured grid version. Thanks in advance.
Danyang

  Thanks,

     Matt

    Danyang

      Thanks,

        Matt

        Otherwise, I should use DMPlexCreateFromCellListParallel
        instead if the input is local mesh.

        Below is the test code I use, results from method 1 is wrong
        and that from method 2 is correct. Would you please help to
        check if I did anything wrong with DMPlexCreateFromCellList
        input?

        !test with 4 processor, global num_cells = 8268, global
        num_nodes = 4250

        !correct results

         check rank            2  istart         2034 iend         3116
         check rank            3  istart         2148 iend         3293
         check rank            1  istart         2044 iend         3133
         check rank            0  istart         2042 iend         3131

        !wrong results

          check rank            0  istart 8268  iend        12518
          check rank            1  istart 8268  iend        12518
          check rank            2  istart 8268  iend        12518
          check rank            3  istart 8268  iend        12518


              !c *************    test part *********************
              !c method 1: create DMPlex from cell list, same
        duplicated global meshes over all processors
              !c the input parameters num_cells, num_nodes,
        dmplex_cells, dmplex_verts are all global parameters (global
        mesh data)
              call
        DMPlexCreateFromCellList(Petsc_Comm_World,ndim,num_cells, &
        num_nodes,num_nodes_per_cell,      &
        Petsc_True,dmplex_cells,ndim,      &
        dmplex_verts,dmda_flow%da,ierr)
              CHKERRQ(ierr)


              !c method 2: create DMPlex from Gmsh file, for test
        purpose, this works fine, each processor gets its own part
              call DMPlexCreateFromFile(Petsc_Comm_World, &
        prefix(:l_prfx)//'.msh',0, &
        dmda_flow%da,ierr)
              CHKERRQ(ierr)

              !c *************end of test part*********************


              distributedMesh = PETSC_NULL_OBJECT

              !c distribute mesh over processes
              call DMPlexDistribute(dmda_flow%da,0,PETSC_NULL_OBJECT, &
        distributedMesh,ierr)
              CHKERRQ(ierr)

              !c destroy original global mesh after distribution
              if (distributedMesh /= PETSC_NULL_OBJECT) then
                call DMDestroy(dmda_flow%da,ierr)
                CHKERRQ(ierr)
                !c set the global mesh as distributed mesh
                dmda_flow%da = distributedMesh
              end if

              !c get coordinates
              call DMGetCoordinatesLocal(dmda_flow%da,gc,ierr)
              CHKERRQ(ierr)

              call DMGetCoordinateDM(dmda_flow%da,cda,ierr)
              CHKERRQ(ierr)

              call DMGetDefaultSection(cda,cs,ierr)
              CHKERRQ(ierr)

              call PetscSectionGetChart(cs,istart,iend,ierr)
              CHKERRQ(ierr)

        #ifdef DEBUG
                if(info_debug > 0) then
                  write(*,*) "check rank ",rank," istart ",istart,"
        iend ",iend
                end if
        #endif


        Thanks and regards,

        Danyang




    -- 
    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/%7Emk51/>




--
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/%7Emk51/>