merge_test.cpp

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#include <vector>
#include <utility>
#include <iostream>
using namespace std;
using namespace moab;

#include "moab/Core.hpp"
#include "moab/Interface.hpp"
#include "moab/Range.hpp"

Interface* gMB = 0;

class EntityCount
{
  public:
    unsigned int node;
    unsigned int edge;
    unsigned int quad;
    unsigned int tri;
    unsigned int hex;
    unsigned int tet;

    EntityCount();

    ErrorCode get_counts();
    ErrorCode create_adjacencies( Range& entities, int adj_dim );
    void copy_counts( EntityCount& count );
    void print();
};

EntityCount::EntityCount()
{
    node = 0;
    edge = 0;
    quad = 0;
    tri  = 0;
    hex  = 0;
    tet  = 0;
}

void EntityCount::copy_counts( EntityCount& count )
{
    node = count.node;
    edge = count.edge;
    quad = count.quad;
    tri  = count.tri;
    hex  = count.hex;
    tet  = count.tet;
}

ErrorCode EntityCount::get_counts()
{
    Range entities;
    int do_create = edge == 0;

    if( gMB->get_entities_by_type( 0, MBVERTEX, entities ) != MB_SUCCESS ) return MB_FAILURE;
    node = entities.size();

    entities.clear();
    if( gMB->get_entities_by_type( 0, MBHEX, entities ) != MB_SUCCESS ) return MB_FAILURE;
    hex = entities.size();
    if( hex > 0 && do_create )
    {
        if( create_adjacencies( entities, 2 ) != MB_SUCCESS ) return MB_FAILURE;
        if( create_adjacencies( entities, 1 ) != MB_SUCCESS ) return MB_FAILURE;
    }

    entities.clear();
    if( gMB->get_entities_by_type( 0, MBQUAD, entities ) != MB_SUCCESS ) return MB_FAILURE;
    quad = entities.size();
    if( quad > 0 && do_create )
    {

        if( create_adjacencies( entities, 1 ) != MB_SUCCESS ) return MB_FAILURE;
    }

    entities.clear();
    if( gMB->get_entities_by_type( 0, MBTET, entities ) != MB_SUCCESS ) return MB_FAILURE;
    tet = entities.size();
    if( tet > 0 && do_create )
    {
        if( create_adjacencies( entities, 2 ) != MB_SUCCESS ) return MB_FAILURE;
        if( create_adjacencies( entities, 1 ) != MB_SUCCESS ) return MB_FAILURE;
    }

    entities.clear();
    if( gMB->get_entities_by_type( 0, MBTRI, entities ) != MB_SUCCESS ) return MB_FAILURE;
    tri = entities.size();
    if( tri > 0 && do_create )
    {
        if( create_adjacencies( entities, 1 ) != MB_SUCCESS ) return MB_FAILURE;
    }

    entities.clear();
    if( gMB->get_entities_by_type( 0, MBEDGE, entities ) != MB_SUCCESS ) return MB_FAILURE;
    edge = entities.size();

    return MB_SUCCESS;
}

ErrorCode EntityCount::create_adjacencies( Range& entities, int adj_dim )
{
    ErrorCode result;
    Range::iterator iter;
    std::vector< EntityHandle > adjacencies;

    for( iter = entities.begin(); iter != entities.end(); ++iter )
    {
        result = gMB->get_adjacencies( &*iter, 1, adj_dim, true, adjacencies );
        if( result != MB_SUCCESS ) break;
    }

    return result;
}

void EntityCount::print()
{
    std::cout << "   Vertices: " << node << std::endl;
    cout << "   Edges: " << edge << endl;
    if( quad > 0 ) cout << "   Quad Elements: " << quad << endl;
    if( hex > 0 ) cout << "   Hex Elements: " << hex << endl;
    if( tri > 0 ) cout << "   Tri Elements: " << tri << endl;
    if( tet > 0 ) cout << "   Tet Elements: " << tet << endl;
}

bool points_are_coincident( const double* first, const double* second )
{
    double diff[3];
    diff[0]       = first[0] - second[0];
    diff[1]       = first[1] - second[1];
    diff[2]       = first[2] - second[2];
    double length = diff[0] * diff[0] + diff[1] * diff[1] + diff[2] * diff[2];

    if( fabs( length ) < .001 ) return true;

    return false;
}

// dumb n^2 coincident node algorithm
ErrorCode find_coincident_nodes( Range vertices, std::vector< std::pair< EntityHandle, EntityHandle > >& coin_nodes )
{
    double first_coords[3], second_coords[3];
    Range::iterator iter, jter;
    std::pair< EntityHandle, EntityHandle > coincident_pair;
    ErrorCode result;

    for( iter = vertices.begin(); iter != vertices.end(); ++iter )
    {
        result = gMB->get_coords( &*iter, 1, first_coords );
        if( result != MB_SUCCESS ) return result;

        for( jter = iter; jter != vertices.end(); ++jter )
        {
            if( *iter != *jter )
            {
                result = gMB->get_coords( &*jter, 1, second_coords );
                if( result != MB_SUCCESS ) return result;

                if( points_are_coincident( first_coords, second_coords ) )
                {
                    coincident_pair.first  = *iter;
                    coincident_pair.second = *jter;
                    coin_nodes.push_back( coincident_pair );
                }
            }
        }
    }
    return MB_SUCCESS;
}

ErrorCode find_coincident_edges( Range entities, std::vector< std::pair< EntityHandle, EntityHandle > >& coin_edges )
{
    double coords1[3], coords2[3], coords3[3];
    Range::iterator iter, jter;
    std::vector< EntityHandle > conn( 2 );
    std::pair< EntityHandle, EntityHandle > coincident_pair;

    for( iter = entities.begin(); iter != entities.end(); ++iter )
    {
        if( gMB->get_connectivity( &*iter, 1, conn ) != MB_SUCCESS ) return MB_FAILURE;

        // Get the coordinates for the edge endpoints.
        if( gMB->get_coords( &conn[0], 1, coords1 ) != MB_SUCCESS ) return MB_FAILURE;

        if( gMB->get_coords( &conn[1], 1, coords2 ) != MB_SUCCESS ) return MB_FAILURE;

        for( jter = iter; jter != entities.end(); ++jter )
        {
            if( *iter != *jter )
            {
                // Edges should be the same sense to merge.
                if( gMB->get_connectivity( &*jter, 1, conn ) != MB_SUCCESS ) return MB_FAILURE;

                if( gMB->get_coords( &conn[0], 1, coords3 ) != MB_SUCCESS ) return MB_FAILURE;

                if( points_are_coincident( coords1, coords3 ) )
                {
                    if( gMB->get_coords( &conn[1], 1, coords3 ) != MB_SUCCESS ) return MB_FAILURE;

                    if( points_are_coincident( coords2, coords3 ) )
                    {
                        coincident_pair.first  = *iter;
                        coincident_pair.second = *jter;
                        coin_edges.push_back( coincident_pair );
                    }
                }
            }
        }
    }

    return MB_SUCCESS;
}

ErrorCode find_coincident_elements( Range entities,
                                    int num_nodes,
                                    std::vector< std::pair< EntityHandle, EntityHandle > >& coin )
{
    double coords1[8][3], coords2[8][3];
    Range::iterator iter, jter;
    std::vector< EntityHandle > conn( 8 );
    std::pair< EntityHandle, EntityHandle > coincident_pair;
    int i = 0, j = 0, ii = 0;

    for( iter = entities.begin(); iter != entities.end(); ++iter )
    {
        // Get the coordinates for the element corners.
        if( gMB->get_connectivity( &*iter, 1, conn ) != MB_SUCCESS ) return MB_FAILURE;
        for( ii = 0; ii < num_nodes; ii++ )
        {
            if( gMB->get_coords( &conn[ii], 1, coords1[ii] ) != MB_SUCCESS ) return MB_FAILURE;
        }

        for( jter = iter; jter != entities.end(); ++jter )
        {
            if( *iter != *jter )
            {
                // Elements should be the same sense to merge.
                if( gMB->get_connectivity( &*jter, 1, conn ) != MB_SUCCESS ) return MB_FAILURE;

                if( gMB->get_coords( &conn[0], 1, coords2[0] ) != MB_SUCCESS ) return MB_FAILURE;

                // Find if first node is coincident before testing the rest.
                for( i = 0; i < num_nodes; i++ )
                {
                    if( points_are_coincident( coords1[i], coords2[0] ) ) break;
                }

                if( i < num_nodes )
                {
                    for( ii = 1; ii < num_nodes; ii++ )
                    {
                        if( gMB->get_coords( &conn[ii], 1, coords2[ii] ) != MB_SUCCESS ) return MB_FAILURE;
                    }

                    for( j = 1; j < num_nodes; j++ )
                    {
                        if( !points_are_coincident( coords1[j], coords2[( j + i ) % num_nodes] ) ) break;
                    }

                    if( j == num_nodes )

                    {
                        coincident_pair.first  = *iter;
                        coincident_pair.second = *jter;
                        coin.push_back( coincident_pair );
                    }
                }
            }
        }
    }

    return MB_SUCCESS;
}

ErrorCode coincident_counts( EntityCount& curr_count, EntityCount& diff_count )
{
    Range entities;
    std::vector< std::pair< EntityHandle, EntityHandle > > coincident;

    if( curr_count.node > 0 )
    {
        if( gMB->get_entities_by_type( 0, MBVERTEX, entities ) != MB_SUCCESS ) return MB_FAILURE;
        find_coincident_nodes( entities, coincident );
        diff_count.node = coincident.size();
        entities.clear();
        coincident.clear();
    }
    if( curr_count.edge > 0 )
    {
        if( gMB->get_entities_by_type( 0, MBEDGE, entities ) != MB_SUCCESS ) return MB_FAILURE;
        find_coincident_edges( entities, coincident );
        diff_count.edge = coincident.size();
        entities.clear();
        coincident.clear();
    }
    if( curr_count.quad > 0 )
    {
        if( gMB->get_entities_by_type( 0, MBQUAD, entities ) != MB_SUCCESS ) return MB_FAILURE;
        find_coincident_elements( entities, 4, coincident );
        diff_count.quad = coincident.size();
        entities.clear();
        coincident.clear();
    }
    if( curr_count.tri > 0 )
    {
        if( gMB->get_entities_by_type( 0, MBTRI, entities ) != MB_SUCCESS ) return MB_FAILURE;
        find_coincident_elements( entities, 3, coincident );
        diff_count.tri = coincident.size();
        entities.clear();
        coincident.clear();
    }
    if( curr_count.tet > 0 )
    {
        if( gMB->get_entities_by_type( 0, MBTET, entities ) != MB_SUCCESS ) return MB_FAILURE;
        find_coincident_elements( entities, 4, coincident );
        diff_count.tet = coincident.size();
        entities.clear();
        coincident.clear();
    }
    if( curr_count.hex > 0 )
    {
        if( gMB->get_entities_by_type( 0, MBHEX, entities ) != MB_SUCCESS ) return MB_FAILURE;
        find_coincident_elements( entities, 8, coincident );
        diff_count.hex = coincident.size();
        entities.clear();
        coincident.clear();
    }

    return MB_SUCCESS;
}

ErrorCode merge_top_down( EntityCount& init_count, EntityCount& curr_count )
{
    Range entities;
    EntityCount diff_count;
    std::vector< std::pair< EntityHandle, EntityHandle > > coincident;

    // Find how many objects of each type need to be merged.
    if( coincident_counts( curr_count, diff_count ) != MB_SUCCESS ) return MB_FAILURE;

    // Find the top level object to merge.
    if( diff_count.hex > 0 )
    {
        if( gMB->get_entities_by_type( 0, MBHEX, entities ) != MB_SUCCESS ) return MB_FAILURE;
        find_coincident_elements( entities, 8, coincident );
    }
    else if( diff_count.quad > 0 )
    {
        if( gMB->get_entities_by_type( 0, MBQUAD, entities ) != MB_SUCCESS ) return MB_FAILURE;
        find_coincident_elements( entities, 4, coincident );
    }
    else if( diff_count.tet > 0 )
    {
        if( gMB->get_entities_by_type( 0, MBTET, entities ) != MB_SUCCESS ) return MB_FAILURE;
        find_coincident_elements( entities, 4, coincident );
    }
    else if( diff_count.tri > 0 )

    {
        if( gMB->get_entities_by_type( 0, MBTRI, entities ) != MB_SUCCESS ) return MB_FAILURE;
        find_coincident_elements( entities, 3, coincident );
    }
    else if( diff_count.edge > 0 )
    {
        if( gMB->get_entities_by_type( 0, MBEDGE, entities ) != MB_SUCCESS ) return MB_FAILURE;
        find_coincident_edges( entities, coincident );
    }

    std::vector< std::pair< EntityHandle, EntityHandle > >::iterator iter;
    for( iter = coincident.begin(); iter != coincident.end(); ++iter )
        gMB->merge_entities( ( *iter ).first, ( *iter ).second, false, true );

    // Get the new entity totals.
    curr_count.get_counts();

    // Make sure we didn't merge anything.
    if( init_count.node != curr_count.node || init_count.edge != curr_count.edge ||
        init_count.quad != curr_count.quad || init_count.tri != curr_count.tri || init_count.hex != curr_count.hex ||
        init_count.tet != curr_count.tet )
    {
        cout << "***ERROR: Merged top down when not using auto merge.***" << endl;
        return MB_FAILURE;
    }

    return MB_SUCCESS;
}

ErrorCode merge_nodes( EntityCount& init_count, EntityCount& curr_count )
{
    cout << "Merging Coincident Nodes:" << endl;

    // Get the list of vertices from the database.
    Range vertices;
    ErrorCode result = gMB->get_entities_by_type( 0, MBVERTEX, vertices );
    if( result != MB_SUCCESS ) return result;

    // find the coincident node pairs
    std::vector< std::pair< EntityHandle, EntityHandle > > coincident_nodes;
    find_coincident_nodes( vertices, coincident_nodes );

    // merge the coincident nodes
    std::vector< std::pair< EntityHandle, EntityHandle > >::iterator iter;
    for( iter = coincident_nodes.begin(); iter != coincident_nodes.end(); ++iter )
    {
        cout << "   Coincident nodes: " << ( *iter ).first << "-" << ( *iter ).second << endl;
        result = gMB->merge_entities( ( *iter ).first, ( *iter ).second, false, true );
        if( result != MB_SUCCESS ) return result;
    }

    // Get the reduced list of vertices.
    curr_count.get_counts();

    // Make sure the coincident nodes were all merged.
    if( init_count.node - curr_count.node != coincident_nodes.size() )
    {
        cout << "***ERROR: Not all coincident nodes were merged.***" << endl;
        return MB_FAILURE;
    }

    init_count.node = curr_count.node;

    // Make sure we didn't merge anything else.
    if( init_count.edge != curr_count.edge || init_count.quad != curr_count.quad || init_count.tri != curr_count.tri ||
        init_count.hex != curr_count.hex || init_count.tet != curr_count.tet )
    {
        cout << "***ERROR: Merged other objects when merging nodes.***" << endl;
        return MB_FAILURE;
    }

    return MB_SUCCESS;
}

ErrorCode merge_edges( EntityCount& init_count, EntityCount& curr_count )
{
    cout << "Merging Coincident Edges:" << endl;

    // Get the list of entities from the database.
    Range entities;
    ErrorCode result = gMB->get_entities_by_type( 0, MBEDGE, entities );
    if( result != MB_SUCCESS ) return result;

    // find the coincident edge pairs
    std::vector< std::pair< EntityHandle, EntityHandle > > coincident_edges;
    find_coincident_edges( entities, coincident_edges );

    // merge the coincident edges
    unsigned long id1, id2;
    std::vector< std::pair< EntityHandle, EntityHandle > >::iterator iter;
    for( iter = coincident_edges.begin(); iter != coincident_edges.end(); ++iter )
    {
        id1 = gMB->id_from_handle( ( *iter ).first );
        id2 = gMB->id_from_handle( ( *iter ).second );
        cout << "   Coincident edges: " << id1 << "-" << id2 << endl;
        result = gMB->merge_entities( ( *iter ).first, ( *iter ).second, false, true );
        if( result != MB_SUCCESS ) return result;
    }

    // Get the reduced list of edges.
    curr_count.get_counts();

    // Make sure the coincident edges were all merged.
    if( init_count.edge - curr_count.edge != coincident_edges.size() )
    {
        cout << "***ERROR: Not all coincident edges were merged.***" << endl;
        return MB_FAILURE;
    }

    init_count.edge = curr_count.edge;

    // Make sure we didn't merge anything else.
    if( init_count.node != curr_count.node || init_count.quad != curr_count.quad || init_count.tri != curr_count.tri ||
        init_count.hex != curr_count.hex || init_count.tet != curr_count.tet )
    {
        cout << "***ERROR: Merged other objects when merging edges.***" << endl;
        return MB_FAILURE;
    }

    return MB_SUCCESS;
}

ErrorCode merge_2D_elem( EntityCount& init_count, EntityCount& curr_count )
{
    cout << "Merging Coincident 2D Elements:" << endl;

    // Get the list of tris from the database.
    Range entities;
    ErrorCode result = gMB->get_entities_by_type( 0, MBTRI, entities );
    if( result != MB_SUCCESS ) return result;

    // find the coincident tri pairs
    std::vector< std::pair< EntityHandle, EntityHandle > > coincident;
    find_coincident_elements( entities, 3, coincident );

    // merge the coincident tris
    unsigned long id1, id2;
    unsigned int tri_diff = coincident.size();
    std::vector< std::pair< EntityHandle, EntityHandle > >::iterator iter;
    for( iter = coincident.begin(); iter != coincident.end(); ++iter )
    {
        id1 = gMB->id_from_handle( ( *iter ).first );
        id2 = gMB->id_from_handle( ( *iter ).second );
        cout << "   Coincident tris: " << id1 << "-" << id2 << endl;
        result = gMB->merge_entities( ( *iter ).first, ( *iter ).second, false, true );

        if( result != MB_SUCCESS ) return result;
    }

    // Get the list of quads from the database.
    entities.clear();
    result = gMB->get_entities_by_type( 0, MBQUAD, entities );
    if( result != MB_SUCCESS ) return result;

    // find the coincident tri pairs
    coincident.clear();
    find_coincident_elements( entities, 4, coincident );

    // merge the coincident tris
    unsigned int quad_diff = coincident.size();
    for( iter = coincident.begin(); iter != coincident.end(); ++iter )
    {
        id1 = gMB->id_from_handle( ( *iter ).first );
        id2 = gMB->id_from_handle( ( *iter ).second );
        cout << "   Coincident quads: " << id1 << "-" << id2 << endl;
        result = gMB->merge_entities( ( *iter ).first, ( *iter ).second, false, true );
        if( result != MB_SUCCESS ) return result;
    }

    // Get the reduced list of faces.
    curr_count.get_counts();

    // Make sure the coincident faces were all merged.
    if( init_count.tri - curr_count.tri != tri_diff )
    {
        cout << "***ERROR: Not all coincident tris were merged.***" << endl;
        return MB_FAILURE;
    }
    if( init_count.quad - curr_count.quad != quad_diff )
    {
        cout << "***ERROR: Not all coincident quads were merged.***" << endl;
        return MB_FAILURE;
    }

    init_count.tri  = curr_count.tri;
    init_count.quad = curr_count.quad;

    // Make sure we didn't merge anything else.
    if( init_count.node != curr_count.node || init_count.edge != curr_count.edge || init_count.hex != curr_count.hex ||
        init_count.tet != curr_count.tet )
    {
        cout << "***ERROR: Merged other objects when merging faces.***" << endl;
        return MB_FAILURE;
    }

    return MB_SUCCESS;
}

ErrorCode merge_3D_elem( EntityCount& init_count, EntityCount& curr_count )
{
    cout << "Merging Coincident 3D Elements:" << endl;

    // Get the list of tets from the database.
    Range entities;
    ErrorCode result = gMB->get_entities_by_type( 0, MBTET, entities );
    if( result != MB_SUCCESS ) return result;

    // find the coincident tet pairs
    std::vector< std::pair< EntityHandle, EntityHandle > > coincident;
    find_coincident_elements( entities, 4, coincident );

    // merge the coincident tets
    unsigned long id1, id2;
    unsigned int tet_diff = coincident.size();
    std::vector< std::pair< EntityHandle, EntityHandle > >::iterator iter;
    for( iter = coincident.begin(); iter != coincident.end(); ++iter )
    {
        id1 = gMB->id_from_handle( ( *iter ).first );
        id2 = gMB->id_from_handle( ( *iter ).second );
        cout << "   Coincident tets: " << id1 << "-" << id2 << endl;
        result = gMB->merge_entities( ( *iter ).first, ( *iter ).second, false, true );
        if( result != MB_SUCCESS ) return result;
    }

    // Get the list of hexs from the database.
    entities.clear();
    result = gMB->get_entities_by_type( 0, MBHEX, entities );
    if( result != MB_SUCCESS ) return result;

    // find the coincident hex pairs
    coincident.clear();
    find_coincident_elements( entities, 8, coincident );

    // merge the coincident tris
    unsigned int hex_diff = coincident.size();
    for( iter = coincident.begin(); iter != coincident.end(); ++iter )
    {
        id1 = gMB->id_from_handle( ( *iter ).first );
        id2 = gMB->id_from_handle( ( *iter ).second );
        cout << "   Coincident hexs: " << id1 << "-" << id2 << endl;
        result = gMB->merge_entities( ( *iter ).first, ( *iter ).second, false, true );
        if( result != MB_SUCCESS ) return result;
    }

    // Get the reduced list of elements.
    curr_count.get_counts();

    // Make sure the coincident elements were all merged.
    if( init_count.tet - curr_count.tet != tet_diff )
    {
        cout << "***ERROR: Not all coincident tets were merged.***" << endl;
        return MB_FAILURE;
    }
    if( init_count.hex - curr_count.hex != hex_diff )
    {
        cout << "***ERROR: Not all coincident hexs were merged.***" << endl;
        return MB_FAILURE;
    }

    init_count.tet = curr_count.tet;
    init_count.hex = curr_count.hex;

    // Make sure we didn't merge anything else.
    if( init_count.node != curr_count.node || init_count.edge != curr_count.edge ||
        init_count.quad != curr_count.quad || init_count.tri != curr_count.tri )
    {
        cout << "***ERROR: Merged other objects when merging elements.***" << endl;
        return MB_FAILURE;
    }

    return MB_SUCCESS;
}

ErrorCode read_file( std::string& file_name, EntityCount& counts )
{
    // Make sure the database is empty.
    gMB->delete_mesh();

    // Read the model from the file.
    if( gMB->load_mesh( file_name.c_str(), 0 ) != MB_SUCCESS )
    {
        cout << "***ERROR: Unable to load mesh file.***" << endl;
        return MB_FAILURE;
    }

    // Get the number of each entity types in the mesh.
    if( counts.get_counts() != MB_SUCCESS )
    {
        cout << "***ERROR: Unable to get entity list counts.***" << endl;
        return MB_FAILURE;
    }

    return MB_SUCCESS;
}

ErrorCode write_file( std::string& file_name )
{
    // get the block tag
    ErrorCode result;
    Range block_range;
    Tag block_tag;

    if( gMB->tag_get_handle( "MATERIAL_SET", block_tag ) == MB_SUCCESS )
    {
        // get all the blocks
        result = gMB->get_entities_by_type_and_tag( 0, MBENTITYSET, &block_tag, 0, 1, block_range );
        if( result != MB_SUCCESS ) return result;
    }

    // transfer range contents into vectors
    std::vector< EntityHandle > output_list;

    Range::iterator range_iter, end_iter;
    range_iter = block_range.begin();
    end_iter   = block_range.end();

    for( ; range_iter != end_iter; ++range_iter )
    {
        int id;
        result = gMB->tag_get_handle( "MATERIAL_SET", block_tag );
        if( result != MB_SUCCESS ) return result;

        result = gMB->tag_get_data( block_tag, &*range_iter, 1, &id );
        if( result != MB_SUCCESS ) return result;

        // if(id != 2)
        output_list.push_back( *range_iter );
    }

    // write the file
    static std::string mrg_splice( ".mrg" );
    file_name.insert( file_name.size() - 2, mrg_splice );
    result = gMB->write_mesh( file_name.c_str(), &output_list[0], output_list.size() );

    return result;
}

ErrorCode process_td_auto_merge( std::string& file_name )
{
    EntityCount init_count;
    EntityCount curr_count;
    EntityCount diff_count;

    // Read in the mesh and get the number of entities of each type.
    if( read_file( file_name, init_count ) != MB_SUCCESS ) return MB_FAILURE;

    // Copy the initial counts into the current count object.
    curr_count.copy_counts( init_count );

    // Print out the list of initial objects.
    cout << "Initial Entities:" << endl;
    curr_count.print();

    // Try auto merging from the top down.
    Range entities;
    std::vector< std::pair< EntityHandle, EntityHandle > > coincident;

    // Find how many objects of each type need to be merged.
    if( coincident_counts( curr_count, diff_count ) != MB_SUCCESS ) return MB_FAILURE;

    // Find the top level object to merge.
    if( diff_count.hex > 0 )
    {
        if( gMB->get_entities_by_type( 0, MBHEX, entities ) != MB_SUCCESS ) return MB_FAILURE;
        find_coincident_elements( entities, 8, coincident );
    }
    else if( diff_count.quad > 0 )
    {
        if( gMB->get_entities_by_type( 0, MBQUAD, entities ) != MB_SUCCESS ) return MB_FAILURE;
        find_coincident_elements( entities, 4, coincident );
    }
    else if( diff_count.tet > 0 )
    {
        if( gMB->get_entities_by_type( 0, MBTET, entities ) != MB_SUCCESS ) return MB_FAILURE;
        find_coincident_elements( entities, 4, coincident );
    }
    else if( diff_count.tri > 0 )
    {
        if( gMB->get_entities_by_type( 0, MBTRI, entities ) != MB_SUCCESS ) return MB_FAILURE;
        find_coincident_elements( entities, 3, coincident );
    }
    else if( diff_count.edge > 0 )
    {
        if( gMB->get_entities_by_type( 0, MBEDGE, entities ) != MB_SUCCESS ) return MB_FAILURE;
        find_coincident_edges( entities, coincident );
    }
    else if( diff_count.node > 0 )
    {
        if( gMB->get_entities_by_type( 0, MBVERTEX, entities ) != MB_SUCCESS ) return MB_FAILURE;
        find_coincident_nodes( entities, coincident );
    }

    cout << "Merging coincident entities(top down)..." << endl;
    std::vector< std::pair< EntityHandle, EntityHandle > >::iterator iter;
    for( iter = coincident.begin(); iter != coincident.end(); ++iter )
        gMB->merge_entities( ( *iter ).first, ( *iter ).second, true, true );

    // Get the new entity totals.
    if( curr_count.get_counts() != MB_SUCCESS )
    {
        cout << "***ERROR: Unable to get entity list counts.***" << endl;
        return MB_FAILURE;
    }

    // Make sure we merged everything.
    if( init_count.node - curr_count.node != diff_count.node || init_count.edge - curr_count.edge != diff_count.edge ||
        init_count.quad - curr_count.quad != diff_count.quad || init_count.tri - curr_count.tri != diff_count.tri ||
        init_count.hex - curr_count.hex != diff_count.hex || init_count.tet - curr_count.tet != diff_count.tet )
    {
        cout << "***ERROR: Not all coincident objects merged automatically.***" << endl;
        curr_count.print();
        return MB_FAILURE;
    }

    // Print out the final list of objects.
    cout << "Final Entities:" << endl;
    curr_count.print();

    return MB_SUCCESS;
}

ErrorCode process_mo_auto_merge( std::string& file_name )
{
    EntityCount init_count;
    EntityCount curr_count;
    EntityCount diff_count;

    // Read in the mesh and get the number of entities of each type.
    if( read_file( file_name, init_count ) != MB_SUCCESS ) return MB_FAILURE;

    // Copy the initial counts into the current count object.
    curr_count.copy_counts( init_count );

    // Print out the list of initial objects.
    cout << "Initial Entities:" << endl;
    curr_count.print();

    // Try auto merging from the middle out.
    Range entities;
    std::vector< std::pair< EntityHandle, EntityHandle > > coincident;

    // Find how many objects of each type need to be merged.
    if( coincident_counts( curr_count, diff_count ) != MB_SUCCESS ) return MB_FAILURE;

    // Start merge at the edge level if present.
    if( diff_count.edge > 0 )
    {
        if( gMB->get_entities_by_type( 0, MBEDGE, entities ) != MB_SUCCESS ) return MB_FAILURE;
        find_coincident_edges( entities, coincident );
    }
    else
    {
        if( gMB->get_entities_by_type( 0, MBVERTEX, entities ) != MB_SUCCESS ) return MB_FAILURE;
        find_coincident_nodes( entities, coincident );
    }

    cout << "Merging coincident entities(middle out)..." << endl;
    std::vector< std::pair< EntityHandle, EntityHandle > >::iterator iter;
    for( iter = coincident.begin(); iter != coincident.end(); ++iter )

        gMB->merge_entities( ( *iter ).first, ( *iter ).second, true, true );

    // Get the new entity totals.
    if( curr_count.get_counts() != MB_SUCCESS )
    {
        cout << "***ERROR: Unable to get entity list counts.***" << endl;
        return MB_FAILURE;
    }

    // Make sure we merged everything.
    if( init_count.node - curr_count.node != diff_count.node || init_count.edge - curr_count.edge != diff_count.edge ||
        init_count.quad - curr_count.quad != diff_count.quad || init_count.tri - curr_count.tri != diff_count.tri ||
        init_count.hex - curr_count.hex != diff_count.hex || init_count.tet - curr_count.tet != diff_count.tet )
    {
        cout << "***ERROR: Not all coincident objects merged automatically.***" << endl;
        curr_count.print();
        return MB_FAILURE;
    }

    // Print out the final list of objects.
    cout << "Final Entities:" << endl;
    curr_count.print();

    return MB_SUCCESS;
}

ErrorCode process_bu_auto_merge( std::string& file_name )
{
    EntityCount init_count;
    EntityCount curr_count;
    EntityCount diff_count;

    // Read in the mesh and get the number of entities of each type.
    if( read_file( file_name, init_count ) != MB_SUCCESS ) return MB_FAILURE;

    // Copy the initial counts into the current count object.
    curr_count.copy_counts( init_count );

    // Print out the list of initial objects.
    cout << "Initial Entities:" << endl;
    curr_count.print();

    // Try auto merging from the bottom up.
    Range entities;
    std::vector< std::pair< EntityHandle, EntityHandle > > coincident;

    // Find how many objects of each type need to be merged.
    if( coincident_counts( curr_count, diff_count ) != MB_SUCCESS ) return MB_FAILURE;

    // Start merging from the nodes and go up.
    if( gMB->get_entities_by_type( 0, MBVERTEX, entities ) != MB_SUCCESS ) return MB_FAILURE;
    find_coincident_nodes( entities, coincident );

    cout << "Merging coincident entities(bottom up)..." << endl;
    std::vector< std::pair< EntityHandle, EntityHandle > >::iterator iter;
    for( iter = coincident.begin(); iter != coincident.end(); ++iter )
        gMB->merge_entities( ( *iter ).first, ( *iter ).second, true, true );

    // Get the new entity totals.
    if( curr_count.get_counts() != MB_SUCCESS )
    {
        cout << "***ERROR: Unable to get entity list counts.***" << endl;
        return MB_FAILURE;
    }

    // Make sure we merged everything.
    if( init_count.node - curr_count.node != diff_count.node || init_count.edge - curr_count.edge != diff_count.edge ||
        init_count.quad - curr_count.quad != diff_count.quad || init_count.tri - curr_count.tri != diff_count.tri ||
        init_count.hex - curr_count.hex != diff_count.hex || init_count.tet - curr_count.tet != diff_count.tet )
    {
        cout << "***ERROR: Not all coincident objects merged automatically.***" << endl;
        curr_count.print();

        return MB_FAILURE;
    }

    // Print out the final list of objects.
    cout << "Final Entities:" << endl;
    curr_count.print();

    return MB_SUCCESS;
}

ErrorCode process_merge( std::string& file_name )
{
    EntityCount init_count;
    EntityCount curr_count;

    // Read in the mesh and get the number of entities of each type.
    if( read_file( file_name, init_count ) != MB_SUCCESS ) return MB_FAILURE;

    // Copy the initial counts into the current count object.
    curr_count.copy_counts( init_count );

    // Print out the list of initial objects.
    cout << "Initial Entities:" << endl;
    curr_count.print();

    // Try to merge elements before nodes (should fail).
    if( merge_top_down( init_count, curr_count ) != MB_SUCCESS ) return MB_FAILURE;

    // Merge the nodes.
    if( merge_nodes( init_count, curr_count ) != MB_SUCCESS ) return MB_FAILURE;

    // Next, merge the edges.
    if( merge_edges( init_count, curr_count ) != MB_SUCCESS ) return MB_FAILURE;

    // Now, merge the 2D elements.
    if( merge_2D_elem( init_count, curr_count ) != MB_SUCCESS ) return MB_FAILURE;

    // Finally, merge the 3D elements.
    if( merge_3D_elem( init_count, curr_count ) != MB_SUCCESS ) return MB_FAILURE;

    // Print out the final list of objects.
    if( curr_count.get_counts() != MB_SUCCESS )
    {
        cout << "***ERROR: Unable to get entity list counts.***" << endl;
        return MB_FAILURE;
    }
    cout << "Final Entities:" << endl;
    curr_count.print();

    // write the file out (modifies name)
    return write_file( file_name );
}

int main()
{
    ErrorCode result;
    std::string test_files[] = {
        std::string( "test/2barcase1.g" ),  std::string( "test/2barcase2.g" ),  std::string( "test/2hexcase1.g" ),
        std::string( "test/2hexcase2.g" ),  std::string( "test/2hexcase3.g" ),  std::string( "test/2hexcase4.g" ),
        std::string( "test/2hexcase5.g" ),  std::string( "test/2quadcase1.g" ), std::string( "test/2quadcase2.g" ),
        std::string( "test/2quadcase3.g" ), std::string( "test/2quadcase4.g" ), std::string( "test/2tetcase1.g" ),
        std::string( "test/2tetcase2.g" ),  std::string( "test/2tetcase3.g" ),  std::string( "test/2tetcase4.g" ),
        std::string( "test/2tricase1.g" ),  std::string( "test/2tricase2.g" ),  std::string( "test/2tricase3.g" ) };

    // Create the MB database instance.
    gMB = new Core();

    // Loop through the list of test files.
    unsigned int i;
    cout << "---Starting Top Down Auto Merge Tests---" << endl << endl;
    for( i = 0; i < ( sizeof( test_files ) / sizeof( std::string ) ); i++ )
    {
        cout << "---Testing:\"" << test_files[i] << "\"---" << endl;
        result = process_td_auto_merge( test_files[i] );
        if( result == MB_SUCCESS )
            cout << "---Success---";
        else
            cout << "---Failure---";
        cout << endl << endl;
    }

    cout << "---Starting Bottom Up Auto Merge Tests---" << endl << endl;
    for( i = 0; i < ( sizeof( test_files ) / sizeof( std::string ) ); i++ )
    {
        cout << "---Testing:\"" << test_files[i] << "\"---" << endl;
        result = process_bu_auto_merge( test_files[i] );
        if( result == MB_SUCCESS )

            cout << "---Success---";
        else
            cout << "---Failure---";
        cout << endl << endl;
    }

    cout << "---Starting Middle Out Auto Merge Tests---" << endl << endl;
    for( i = 0; i < ( sizeof( test_files ) / sizeof( std::string ) ); i++ )
    {
        cout << "---Testing:\"" << test_files[i] << "\"---" << endl;
        result = process_mo_auto_merge( test_files[i] );
        if( result == MB_SUCCESS )
            cout << "---Success---";
        else
            cout << "---Failure---";

        cout << endl << endl;
    }

    cout << "---Starting Merge Tests---" << endl << endl;
    for( i = 0; i < ( sizeof( test_files ) / sizeof( std::string ) ); i++ )
    {
        cout << "---Testing:\"" << test_files[i] << "\"---" << endl;
        result = process_merge( test_files[i] );
        if( result == MB_SUCCESS )
            cout << "---Success---";
        else
            cout << "---Failure---";
        cout << endl << endl;
    }

    // Destroy the MB database instance.
    delete gMB;
    gMB = NULL;
}