Re: [Libmesh-users] problems with mesh output

[Michael P. <mpo...@pu...>]

Thank you John,

I do have some MPI code before LibMeshInit in my real application.

Also, If I do not call MPI_Finalize at the very end I'm getting warning 
messages from MPI.

Thank you for you explanation with .pvtu, I have changed my code to  
libMesh::VTKIO out(mesh); out.write("mesh1.pvtu");   and this worked.

Do you have any suggestions for  the Problem #2 that I reported?

It seems to me that the problem is that the communicator of the Mesh 
object is smaller than the communicator of the VTK. This causes a 
problem for me.

Thank you,

Michael.

On 06/13/2018 12:01 PM, John Peterson wrote:
>
>
> On Tue, Jun 12, 2018 at 7:48 PM, Povolotskyi, Mykhailo 
> <mpo...@pu... <mailto: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