graph.addPath( source, lhsStage1 );
graph.addPath( lhsStage1, mergeStage );
graph.addPath( mergeStage, lhsStage2 );
graph.addPath( lhsStage2, lhsSink );
graph.addTail( lhsSink );
graph.addPath( source, rhsStage1 );
graph.addPath( rhsStage1, mergeStage );
graph.addPath( mergeStage, rhsStage2 );
graph.addPath( rhsStage2, rhsSink );