//Perform a 2-opt optimization on the given route and return the new route
private static Route TwoOpt(Route orig, ref double costSavings)
{
/*for empty trucks, we cannot find a better path*/
if (orig.ids.Count == 0) {
return null;
} else {
bool foundBetter = false;
double newLen = 0;
int[] betterPath = TwoOpt(orig.ids.ToArray(), ref foundBetter, ref newLen, false);
if (foundBetter) {
Console.WriteLine("** Truck Id {0} : New best Route len : {1:N} Savings = {2:N}", orig.truckId, newLen, newLen - orig.totalDist);
costSavings = orig.totalDist - newLen;
return new Route() {
ids = betterPath.ToList(),
totalDist = newLen,
truckId = orig.truckId,
unusedDemand = orig.unusedDemand
};
} else {
costSavings = 0;
return null;
}
}
}
private static Solution LS2Step(Solution basicSoln, ref double costSavings, ref int trucki, ref int truckj, ref int nodei, ref int nodej, bool exploreAll)
{
Solution betterSol = new Solution();
costSavings = 0;
bool foundBetter = false;
/*try to swap nodes pi and pj between truck_i and truck_j if the capccity constraints are satisfied*/
Route iRoute, jRoute;
for (int i = 0; i < numTrucks - 1; i++) {
iRoute = basicSoln.routes[i];
int freeCapacityIni = iRoute.unusedDemand;
for (int j = i + 1; j < numTrucks; j++) {
jRoute = basicSoln.routes[j];
int freeCapacityInj = jRoute.unusedDemand;
if (iRoute.ids.Count == 0 || jRoute.ids.Count == 0) continue;
double origCost = iRoute.totalDist + jRoute.totalDist;
for (int piIdx = 0; piIdx < iRoute.ids.Count; piIdx++) {
int pi = iRoute.ids[piIdx];
if (pi == 0) continue;
for (int pjIdx = 0; pjIdx < jRoute.ids.Count; pjIdx++) {
int pj = jRoute.ids[pjIdx];
if (pj == 0) continue;
int demi = demands[pi];
int demj = demands[pj];
if ((freeCapacityIni + demi - demj >= 0) && (freeCapacityInj + demj - demi >= 0)) {
List<int> newiPath = new List<int>(iRoute.ids);
newiPath.Remove(pi);
newiPath.Add(pj);
List<int> newjPath = new List<int>(jRoute.ids);
newjPath.Remove(pj);
newjPath.Add(pi);
bool foundBetteri = false, foundBetterj = false;
double newLeni = 0, newLenj = 0;
int[] betteriRoute = TwoOpt(newiPath.ToArray(), ref foundBetteri, ref newLeni, false);
int[] betterjRoute = TwoOpt(newjPath.ToArray(), ref foundBetterj, ref newLenj, false);
double newCost = newLeni + newLenj;
double thisCostSavings = origCost - newCost;
if (thisCostSavings > 0.000001) {
if (thisCostSavings > costSavings) {
costSavings = thisCostSavings;
trucki = i;
truckj = j;
nodei = pi;
nodej = pj;
foundBetter = true;
Route newiRoute = new Route();
if (foundBetteri && betteriRoute != null) {
newiRoute.ids = betteriRoute.ToList();
} else {
newiRoute.ids = newiPath;
}
newiRoute.totalDist = newLeni;
newiRoute.truckId = iRoute.truckId;
newiRoute.unusedDemand = iRoute.unusedDemand + demi - demj;
Route newjRoute = new Route();
if (foundBetterj && betterjRoute != null) {
newjRoute.ids = betterjRoute.ToList();
} else {
newjRoute.ids = newjPath;
}
newjRoute.totalDist = newLenj;
newjRoute.truckId = jRoute.truckId;
newjRoute.unusedDemand = jRoute.unusedDemand + demj - demi;
betterSol = new Solution();
//create the new solution with modified i and j routes
for (int t = 0; t < basicSoln.routes.Count; t++) {
if (t == i) {
betterSol.routes.Add(newiRoute);
} else if (t == j) {
betterSol.routes.Add(newjRoute);
} else {
betterSol.routes.Add(basicSoln.routes[t]);
}
}
if (!exploreAll) {
goto end;
}
}
}
}
}
}
}
}
end:
if (foundBetter) {
return betterSol;
} else {
return null;
}
}
private static Solution GetInitialFeasibleSolution(NodeInfo[] nodes)
{
Solution soln = new Solution();
int currTruck = 1;
bool allDemandSatisfied = false;
HashSet<int> assignedNodes = new HashSet<int>();
while (!allDemandSatisfied && currTruck <= numTrucks) {
int availableCap = truckCapacity;
//iterate over each of the nodes and if any node has not been assigned yet
//to any truck and the capacity constraints of the truck are satisfied, then
//assign this node to this truck.
Route thisRoute = new Route();
thisRoute.ids.Add(0);
thisRoute.truckId = currTruck;
thisRoute.unusedDemand = availableCap;
for (int i = 0; i < nodes.Length; i++) {
if (nodes[i].id != 0) {
int thisNodeId = nodes[i].id;
int thisNodeDemand = demands[thisNodeId];
if (!assignedNodes.Contains(thisNodeId) && availableCap >= thisNodeDemand) {
availableCap -= thisNodeDemand;
assignedNodes.Add(thisNodeId);
thisRoute.ids.Add(thisNodeId);
thisRoute.unusedDemand = availableCap;
if (assignedNodes.Count == nodes.Length - 1) {
allDemandSatisfied = true;
break;
}
}
}
}
//thisRoute.ids.Add(0); /*to keep it consistent with tsp routines*/
CalculateRouteDistance(thisRoute);
soln.routes.Add(thisRoute);
currTruck++;
}
if (!allDemandSatisfied) {
return null;
} else {
//fill up additional trucks with path : 0-0
int usedTrucks = soln.routes.Count;
for (int i = 0; i < numTrucks - usedTrucks; i++) {
soln.routes.Add(new Route() {
ids = new List<int>() {0},
totalDist = 0,
unusedDemand = truckCapacity,
truckId = currTruck++
});
}
return soln;
}
}
private static void CalculateRouteDistance(Route route)
{
double dist = 0;
/*from origin till last node*/
for (int i = 0; i < route.ids.Count - 1; i++) {
dist += distMatrix[route.ids[i], route.ids[i + 1]];
}
dist += distMatrix[route.ids[route.ids.Count - 1], route.ids[0]]; /*add last node to origin*/
route.totalDist = dist;
}
private static Solution LS1Step(Solution basicSoln, ref double costSavings, ref int trucki, ref int truckj)
{
Solution betterSol = new Solution();
bool foundBetter = false;
/*try to move a node from truck_i to truck_j if the capccity constraints are satisfied*/
Route iRoute, jRoute;
for (int i = 0; i < numTrucks; i++) {
iRoute = basicSoln.routes[i];
for (int j = 0; j < numTrucks; j++) {
jRoute = basicSoln.routes[j];
int freeCapacityInj = jRoute.unusedDemand;
if (i == j) continue;
if (freeCapacityInj == 0) continue;
if (iRoute.ids.Count == 0) continue;
List<int> idsToProbe = iRoute.ids.Where(x => x != 0 && demands[x] <= freeCapacityInj).ToList();
for (int k = 0; k < idsToProbe.Count; k++) {
if (idsToProbe[k] != 0) { /*we cannot move the origin from i to j*/
int demandOfThisPointIni = demands[idsToProbe[k]];
if (freeCapacityInj >= demandOfThisPointIni) { /*capccity constraints are satisfied*/
/*move ids[k] from truck_i to truck_j*/
List<int> newiPath = new List<int>(iRoute.ids);
newiPath.Remove(idsToProbe[k]); ;
List<int> newjPath = new List<int>(jRoute.ids);
newjPath.Add(idsToProbe[k]);
double origCost = iRoute.totalDist + jRoute.totalDist;
bool foundBetteri = false, foundBetterj =false;
double newLeni = 0, newLenj = 0;
int[] betteriRoute = TwoOpt(newiPath.ToArray(), ref foundBetteri, ref newLeni, false);
int[] betterjRoute = TwoOpt(newjPath.ToArray(), ref foundBetterj, ref newLenj, false);
double newCost = newLeni + newLenj;
costSavings = origCost-newCost;
if (costSavings > 0.000001) {
trucki = i;
truckj = j;
foundBetter = true;
Route newiRoute = new Route();
if (foundBetteri && betteriRoute != null) {
newiRoute.ids = betteriRoute.ToList();
} else {
newiRoute.ids = iRoute.ids;
}
newiRoute.totalDist = newLeni;
newiRoute.truckId = iRoute.truckId;
newiRoute.unusedDemand = iRoute.unusedDemand + demandOfThisPointIni;
Route newjRoute = new Route();
if (foundBetterj && betterjRoute != null) {
newjRoute.ids = betterjRoute.ToList();
} else {
newjRoute.ids = jRoute.ids;
}
newjRoute.totalDist = newLenj;
newjRoute.truckId = jRoute.truckId;
newjRoute.unusedDemand = jRoute.unusedDemand - demandOfThisPointIni;
//create the new solution with modified i and j routes
for (int t = 0; t < basicSoln.routes.Count; t++) {
if (t == i) {
betterSol.routes.Add(newiRoute);
} else if (t == j) {
betterSol.routes.Add(newjRoute);
} else {
betterSol.routes.Add(basicSoln.routes[t]);
}
}
goto end;
}
}
}
}
}
}
end:
if (foundBetter) {
return betterSol;
} else {
return null;
}
}