LoadPartial.cpp File Reference

Example demonstrating partial loading of mesh files based on tag values. More...

#include <iostream>
#include <vector>
#include "moab/Core.hpp"
#include "MBTagConventions.hpp"

Include dependency graph for LoadPartial.cpp:

Go to the source code of this file.

Macros
#define	NTAGVALS   3

Functions
ErrorCode	get_file_options (int argc, char **argv, string &filename, string &tagName, vector< int > &tagValues)
int	main (int argc, char **argv)

Detailed Description

Example demonstrating partial loading of mesh files based on tag values.

This example shows how to:

• Load only specific parts of a mesh file based on tag values
• Use parallel partition tags to load specific partitions
• Handle file organization in sets for selective loading
• Work with HANDLEID tags for entity identification
• Write partial mesh data to new files

This is particularly useful for parallel applications where each processor needs to load only its assigned portion of a large mesh.

Author

MOAB Development Team

Date

2024

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

Parameters

argc	Number of command line arguments
argv	Command line arguments array

Returns

0 on success, 1 on failure

Definition in file LoadPartial.cpp.

Macro Definition Documentation

NTAGVALS

#define NTAGVALS   3

Definition at line 42 of file LoadPartial.cpp.

Function Documentation

get_file_options()

ErrorCode get_file_options	(	int	argc,
		char **	argv,
		string &	filename,
		string &	tagName,
		vector< int > &	tagValues
	)

Definition at line 48 of file LoadPartial.cpp.

{
    // 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> \c tag_name <value1> <value2> .. \n";
    return MB_SUCCESS;
}

References MB_SUCCESS, and MESH_DIR.

Referenced by main().

main()

int main	(	int	argc,
		char **	argv
	)

Definition at line 79 of file LoadPartial.cpp.

{
    // 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
    MB_CHK_ERR( get_file_options( argc, argv, filename, tagname, tagvals ) );
 
#ifdef MOAB_HAVE_HDF5
    // This file is in the mesh files directory
    MB_CHK_SET_ERR( mb->load_file( filename.c_str(), 0, 0, PARALLEL_PARTITION_TAG_NAME, tagvals.data(),
                                   (int)tagvals.size() ),
                    "Failed to read" );
 
    // If HANDLEID tag present, convert to long, and see what we read from file
    Tag handleid_tag;
    ErrorCode rval = mb->tag_get_handle( "HANDLEID", handleid_tag );
    if( MB_SUCCESS == rval )
    {
        // Convert a few values for a few vertices
        Range verts;
        MB_CHK_SET_ERR( mb->get_entities_by_type( 0, MBVERTEX, verts ), "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";
    }
 
    MB_CHK_SET_ERR( mb->write_file( "part.h5m" ), "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;
}

References ErrorCode, moab::Core::get_entities_by_type(), get_file_options(), moab::Core::load_file(), mb, MB_CHK_ERR, MB_CHK_SET_ERR, MB_SUCCESS, MBVERTEX, NTAGVALS, PARALLEL_PARTITION_TAG_NAME, moab::Range::size(), moab::Core::tag_get_data(), moab::Core::tag_get_handle(), and moab::Core::write_file().