Mesh Oriented datABase  (version 5.5.1)
An array-based unstructured mesh library
HelloParMOAB.cpp

Read mesh into MOAB and resolve/exchange/report shared and ghosted entities
To run: mpiexec -np 4 HelloParMOAB [filename]

It shows how to load the mesh independently, on multiple communicators (with second argument, the number of comms)

mpiexec -np 8 HelloParMOAB [filename] [nbComms]

/** @example HelloParMOAB.cpp \n
* \brief Read mesh into MOAB and resolve/exchange/report shared and ghosted entities \n
* <b>To run</b>: mpiexec -np 4 HelloParMOAB [filename]\n
*
* It shows how to load the mesh independently, on multiple
* communicators (with second argument, the number of comms)
*
* mpiexec -np 8 HelloParMOAB [filename] [nbComms]
*/
#include "moab/Core.hpp"
#ifdef MOAB_HAVE_MPI
#endif
#include <iostream>
using namespace moab;
using namespace std;
string test_file_name = string( MESH_DIR ) + string( "/64bricks_512hex_256part.h5m" );
int main( int argc, char** argv )
{
#ifdef MOAB_HAVE_MPI
MPI_Init( &argc, &argv );
string options;
// Need option handling here for input filename
if( argc > 1 )
{
// User has input a mesh file
test_file_name = argv[1];
}
int nbComms = 1;
if( argc > 2 ) nbComms = atoi( argv[2] );
options = "PARALLEL=READ_PART;PARTITION=PARALLEL_PARTITION;PARALLEL_RESOLVE_SHARED_ENTS";
// Get MOAB instance
Interface* mb = new( std::nothrow ) Core;
if( NULL == mb ) return 1;
MPI_Comm comm;
int global_rank, global_size;
MPI_Comm_rank( MPI_COMM_WORLD, &global_rank );
MPI_Comm_rank( MPI_COMM_WORLD, &global_size );
int color = global_rank % nbComms; // For each angle group a different color
if( nbComms > 1 )
{
// Split the communicator, into ngroups = nbComms
MPI_Comm_split( MPI_COMM_WORLD, color, global_rank, &comm );
}
else
comm = MPI_COMM_WORLD;
// Get the ParallelComm instance
ParallelComm* pcomm = new ParallelComm( mb, comm );
int nprocs = pcomm->proc_config().proc_size();
int rank = pcomm->proc_config().proc_rank();
#ifndef NDEBUG
MPI_Comm rcomm = pcomm->proc_config().proc_comm();
assert( rcomm == comm );
#endif
if( 0 == global_rank )
cout << " global rank:" << global_rank << " color:" << color << " rank:" << rank << " of " << nprocs
<< " processors\n";
if( 1 == global_rank )
cout << " global rank:" << global_rank << " color:" << color << " rank:" << rank << " of " << nprocs
<< " processors\n";
MPI_Barrier( MPI_COMM_WORLD );
if( 0 == global_rank )
cout << "Reading file " << test_file_name << "\n with options: " << options << "\n on " << nprocs
<< " processors on " << nbComms << " communicator(s)\n";
// Read the file with the specified options
ErrorCode rval = mb->load_file( test_file_name.c_str(), 0, options.c_str() );MB_CHK_ERR( rval );
Range shared_ents;
// Get entities shared with all other processors
rval = pcomm->get_shared_entities( -1, shared_ents );MB_CHK_ERR( rval );
// Filter shared entities with not not_owned, which means owned
Range owned_entities;
rval = pcomm->filter_pstatus( shared_ents, PSTATUS_NOT_OWNED, PSTATUS_NOT, -1, &owned_entities );MB_CHK_ERR( rval );
unsigned int nums[4] = { 0 }; // to store the owned entities per dimension
for( int i = 0; i < 4; i++ )
nums[i] = (int)owned_entities.num_of_dimension( i );
vector< int > rbuf( nprocs * 4, 0 );
MPI_Gather( nums, 4, MPI_INT, &rbuf[0], 4, MPI_INT, 0, comm );
// Print the stats gathered:
if( 0 == global_rank )
{
for( int i = 0; i < nprocs; i++ )
cout << " Shared, owned entities on proc " << i << ": " << rbuf[4 * i] << " verts, " << rbuf[4 * i + 1]
<< " edges, " << rbuf[4 * i + 2] << " faces, " << rbuf[4 * i + 3] << " elements" << endl;
}
// Now exchange 1 layer of ghost elements, using vertices as bridge
// (we could have done this as part of reading process, using the PARALLEL_GHOSTS read option)
rval = pcomm->exchange_ghost_cells( 3, // int ghost_dim
0, // int bridge_dim
1, // int num_layers
0, // int addl_ents
true );MB_CHK_ERR( rval ); // bool store_remote_handles
// Repeat the reports, after ghost exchange
shared_ents.clear();
owned_entities.clear();
rval = pcomm->get_shared_entities( -1, shared_ents );MB_CHK_ERR( rval );
rval = pcomm->filter_pstatus( shared_ents, PSTATUS_NOT_OWNED, PSTATUS_NOT, -1, &owned_entities );MB_CHK_ERR( rval );
// Find out how many shared entities of each dimension are owned on this processor
for( int i = 0; i < 4; i++ )
nums[i] = (int)owned_entities.num_of_dimension( i );
// Gather the statistics on processor 0
MPI_Gather( nums, 4, MPI_INT, &rbuf[0], 4, MPI_INT, 0, comm );
if( 0 == global_rank )
{
cout << " \n\n After exchanging one ghost layer: \n";
for( int i = 0; i < nprocs; i++ )
{
cout << " Shared, owned entities on proc " << i << ": " << rbuf[4 * i] << " verts, " << rbuf[4 * i + 1]
<< " edges, " << rbuf[4 * i + 2] << " faces, " << rbuf[4 * i + 3] << " elements" << endl;
}
}
delete mb;
MPI_Finalize();
#else
std::cout << " compile with MPI and hdf5 for this example to work\n";
#endif
return 0;
}