// Propagate
Date startProp = new Date();
final Propagator[] propagator = new Propagator[1];
switch( opts.propagator() ) {
case SparkOptions.propagator_iter:
propagator[0] = new PropIter( pag );
break;
case SparkOptions.propagator_worklist:
propagator[0] = new PropWorklist( pag );
break;
case SparkOptions.propagator_cycle: