LoadPartial.cpp

Load a part of a file
To run: LoadPartial [file] [tag_name] [val1] [val2] ...

In this example, it is shown how to load only a part of one file; the file must be organized in sets. (cherry-picking only the sets we want) The sets to load are identified by a tag name and the tag values for the sets of interest. This procedure is used when reading in parallel, as each processor will load only its part of the file, identified either by partition or by material/block sets by default, this example will load parallel partition sets with values 1, 2, and 5 from ../MeshFiles/unittest/64bricks_1khex.h5m The example will always write the output to a file name part.h5m

/** @example LoadPartial.cpp \n
 * \brief Load a part of a file  \n
 * <b>To run</b>: LoadPartial [file] [tag_name] [val1] [val2] ...\n
 *
 * In this example, it is shown how to load only a part of one file; the file must be organized in
 * sets. (cherry-picking only the sets we want) The sets to load are identified by a tag name and
 * the tag values for the sets of interest. This procedure is used  when reading in parallel, as
 * each processor will load only its part of the file, identified either by partition or by
 * material/block sets by default, this example will load parallel partition sets with values 1, 2,
 * and 5 from ../MeshFiles/unittest/64bricks_1khex.h5m The example will always write the output to a
 * file name part.h5m
 */
 
#include <iostream>
#include <vector>
 
// Include header for MOAB instance and tag conventions for
#include "moab/Core.hpp"
#include "MBTagConventions.hpp"
 
#define NTAGVALS 3
 
using namespace moab;
using namespace std;
 
// Function to parse input parameters
ErrorCode get_file_options( int argc, char** argv, string& filename, string& tagName, vector< int >& tagValues )
{
    // Get mesh filename
    if( argc > 1 )
        filename = string( argv[1] );
    else
        filename = string( MESH_DIR ) + string( "/64bricks_512hex_256part.h5m" );
 
    // Get tag selection options
    if( argc > 2 )
        tagName = string( argv[2] );
    else
        tagName = "USERTAG";
 
    if( argc > 3 )
    {
        tagValues.resize( argc - 3, 0 );
        for( int i = 3; i < argc; ++i )
            tagValues[i - 3] = atoi( argv[i] );
    }
    else
    {
        for( unsigned i = 0; i < tagValues.size(); ++i )
            tagValues[i] = 2 * i + 1;
    }
 
    if( argc > 1 && argc < 4 )  // print usage
        cout << " usage is " << argv[0] << " <file> <tag_name> <value1> <value2> .. \n";
    return MB_SUCCESS;
}
 
int main( int argc, char** argv )
{
    // Get MOAB instance
    Interface* mb = new( std::nothrow ) Core;
    if( NULL == mb ) return 1;
 
    std::string filename, tagname;
    vector< int > tagvals( NTAGVALS );  // Allocate for a maximum of 5 tag values
    ErrorCode rval = get_file_options( argc, argv, filename, tagname, tagvals );MB_CHK_ERR( rval );
 
#ifdef MOAB_HAVE_HDF5
    // This file is in the mesh files directory
    rval = mb->load_file( filename.c_str(), 0, 0, PARALLEL_PARTITION_TAG_NAME, tagvals.data(), (int)tagvals.size() );MB_CHK_SET_ERR( rval, "Failed to read" );
 
    // If HANDLEID tag present, convert to long, and see what we read from file
    Tag handleid_tag;
    rval = mb->tag_get_handle( "HANDLEID", handleid_tag );
    if( MB_SUCCESS == rval )
    {
        // Convert a few values for a few vertices
        Range verts;
        rval = mb->get_entities_by_type( 0, MBVERTEX, verts );MB_CHK_SET_ERR( rval, "Failed to get vertices" );
        vector< long > valsTag( verts.size() );
        rval = mb->tag_get_data( handleid_tag, verts, &valsTag[0] );
        if( MB_SUCCESS == rval ) cout << "First 2 long values recovered: " << valsTag[0] << " " << valsTag[1] << "\n";
    }
 
    rval = mb->write_file( "part.h5m" );MB_CHK_SET_ERR( rval, "Failed to write partial file" );
    cout << "Wrote successfully part.h5m.\n";
 
#else
    std::cout << "Configure MOAB with HDF5 to build and use this example correctly.\n";
#endif
    delete mb;
    return 0;
}