Re: [Libmesh-users] problems with mesh output

[John P. <jwp...@gm...>]

On Tue, Jun 12, 2018 at 7:48 PM, Povolotskyi, Mykhailo <mpo...@pu...>
wrote:

> Dear Libmesh develepers,
>
> I want to create different instances of mesh on several MPI processes.
> Then I want to output the mesh from one MPI process.
>
>
> I am facing problems with the following code:
>
>
> #include "libmesh/libmesh.h"
> #include "libmesh/mesh_generation.h"
> #include "libmesh/mesh.h"
> int main(int argc, char ** argv)
> {
>
>   MPI_Init(&argc, &argv);
>

MPI is already initialized in LibMeshInit, so no need to do this manually
unless your real code does MPI communication before LibMeshInit...


>   {
>     libMesh::LibMeshInit init (argc, argv,MPI_COMM_WORLD);
>     libMesh::Mesh mesh(libMesh::Parallel::Communicator(MPI_COMM_SELF));
>     libMesh::MeshTools::Generation::build_cube (mesh,
>                                                 10, 10, 5, 0.0, 2.0, 0.0,
> 3.0, 0.0, 4.0,libMesh::HEX8);
>
>     int rank;
>     MPI_Comm_rank(MPI_COMM_WORLD, &rank);
>

Again, I'd just use init.comm().rank() to find out the rank.


>
>     if (rank == 0)
>     {
>       mesh.write("mesh1.vtu");
>     }
>   }
>   MPI_Finalize();
>

MPI_Finalize is called in the LibMeshInit destructor, no need to call it
manually.


>   return 0;
> }
>



The problems are as follows:
>
> Problem #1) If I run the code in serial, I'm getting warning:
>
> Warning:  This MeshOutput subclass only supports meshes which have been
> serialized!
> Warning:  This MeshOutput subclass only supports meshes which have been
> serialized!
> The .pvtu extension should be used when writing VTK files in libMesh.
>
>
> My question:
>
> a) how to avoid the first waning about the mesh not being serialized?
>

Unless you have configured libmesh with --enable-parmesh (and therefore
Mesh == DistributedMesh) this warning can be safely ignored.



>
> b) I tried to change the filename to mesh1.pvtu
>
> In this case I'm getting an error message:
>
>
>
> ERROR: Unrecognized file extension: mesh1.pvtu
>    I understand the following:
>

This is just a (possibly unnecessary) limitation of the NamebasedIO class,
it should work (as in misc_ex11 and misc_ex4 if you explicitly construct a
VTKIO object and then call the write() method.

-- 
John