package rinde.sim.pdptw.central;
import static com.google.common.collect.Lists.newArrayList;
import static com.google.common.collect.Sets.newHashSet;
import java.util.Collections;
import java.util.List;
import java.util.Set;
import org.apache.commons.math3.random.MersenneTwister;
import org.apache.commons.math3.random.RandomAdaptor;
import org.apache.commons.math3.random.RandomGenerator;
import rinde.sim.pdptw.central.GlobalStateObject.VehicleStateObject;
import rinde.sim.pdptw.common.ParcelDTO;
import rinde.sim.util.SupplierRng;
import rinde.sim.util.SupplierRng.DefaultSupplierRng;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.LinkedListMultimap;
/**
* A {@link Solver} that constructs random solutions. For each order it first
* randomly selects a vehicle. When all orders are assigned to a vehicle the
* ordering of the pickups and deliveries is shuffled randomly.
*
* @author Rinde van Lon <rinde.vanlon@cs.kuleuven.be>
*/
public class RandomSolver implements Solver {
private final RandomGenerator randomGenerator;
/**
* Creates a new instance using the specified random generator.
* @param rng The random generator to use for creating random solutions.
*/
public RandomSolver(RandomGenerator rng) {
randomGenerator = rng;
}
@Override
public ImmutableList<ImmutableList<ParcelDTO>> solve(GlobalStateObject state) {
final LinkedListMultimap<VehicleStateObject, ParcelDTO> map = LinkedListMultimap
.create();
final Set<ParcelDTO> available = newHashSet(state.availableParcels);
final Set<ParcelDTO> destinations = newHashSet();
for (final VehicleStateObject vso : state.vehicles) {
if (vso.destination != null) {
destinations.add(vso.destination);
}
}
available.removeAll(destinations);
// do random assignment of available parcels
for (final ParcelDTO p : available) {
final int index = randomGenerator.nextInt(state.vehicles.size());
map.put(state.vehicles.get(index), p);
map.put(state.vehicles.get(index), p);
}
final ImmutableList.Builder<ImmutableList<ParcelDTO>> builder = ImmutableList
.builder();
// insert contents, shuffle ordering, insert destination if applicable
for (final VehicleStateObject vso : state.vehicles) {
final List<ParcelDTO> assigned = newArrayList(map.get(vso));
final List<ParcelDTO> conts = newArrayList(vso.contents);
conts.remove(vso.destination);
assigned.addAll(conts);
if (vso.destination != null
&& state.availableParcels.contains(vso.destination)) {
assigned.add(vso.destination);
}
Collections.shuffle(assigned, new RandomAdaptor(randomGenerator));
if (vso.destination != null) {
assigned.add(0, vso.destination);
}
builder.add(ImmutableList.copyOf(assigned));
}
return builder.build();
}
/**
* @return A {@link SupplierRng} for {@link RandomSolver} instances.
*/
public static SupplierRng<Solver> supplier() {
return new DefaultSupplierRng<Solver>() {
@Override
public Solver get(long seed) {
return new RandomSolver(new MersenneTwister(seed));
}
};
}
}