98 lines
3.4 KiB
Java
98 lines
3.4 KiB
Java
// Copyright 2010-2011 Google
|
|
// Licensed under the Apache License, Version 2.0 (the "License");
|
|
// you may not use this file except in compliance with the License.
|
|
// You may obtain a copy of the License at
|
|
//
|
|
// http://www.apache.org/licenses/LICENSE-2.0
|
|
//
|
|
// Unless required by applicable law or agreed to in writing, software
|
|
// distributed under the License is distributed on an "AS IS" BASIS,
|
|
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
|
|
// See the License for the specific language governing permissions and
|
|
// limitations under the License.
|
|
|
|
package com.google.ortools.graph.samples;
|
|
|
|
import com.google.ortools.graph.MaxFlow;
|
|
import com.google.ortools.graph.MinCostFlow;
|
|
import com.google.ortools.graph.StarGraph;
|
|
|
|
/**
|
|
* Sample showing how to model using the flow solver.
|
|
*
|
|
*/
|
|
|
|
public class FlowExample {
|
|
|
|
static {
|
|
System.loadLibrary("jnigraph");
|
|
}
|
|
|
|
|
|
private static void solveMinCostFlow() {
|
|
System.out.println("Min Cost Flow Problem");
|
|
final int numSources = 4;
|
|
final int numTargets = 4;
|
|
final int[][] costs = {{90, 75, 75, 80},
|
|
{35, 85, 55, 65},
|
|
{125, 95, 90, 105},
|
|
{45, 110, 95, 115}};
|
|
final int expectedCost = 275;
|
|
StarGraph graph = new StarGraph(numSources + numTargets,
|
|
numSources * numTargets);
|
|
MinCostFlow minCostFlow = new MinCostFlow(graph);
|
|
for (int source = 0; source < numSources; ++source) {
|
|
for (int target = 0; target < numTargets; ++target) {
|
|
final int arc = graph.addArc(source, numSources + target);
|
|
minCostFlow.setArcUnitCost(arc, costs[source][target]);
|
|
minCostFlow.setArcCapacity(arc, 1);
|
|
}
|
|
}
|
|
|
|
for (int source = 0; source < numSources; ++source) {
|
|
minCostFlow.setNodeSupply(source, 1);
|
|
}
|
|
for (int target = 0; target < numTargets; ++target) {
|
|
minCostFlow.setNodeSupply(numSources + target, -1);
|
|
}
|
|
if (minCostFlow.solve()) {
|
|
final long totalFlowCost = minCostFlow.getOptimalCost();
|
|
System.out.println("total flow = " + totalFlowCost + "/" + expectedCost);
|
|
} else {
|
|
System.out.println("No solution found");
|
|
}
|
|
}
|
|
|
|
private static void solveMaxFlow() {
|
|
System.out.println("Max Flow Problem");
|
|
final int numNodes = 6;
|
|
final int numArcs = 9;
|
|
final int[] tails = {0, 0, 0, 0, 1, 2, 3, 3, 4};
|
|
final int[] heads = {1, 2, 3, 4, 3, 4, 4, 5, 5};
|
|
final int[] capacities = {5, 8, 5, 3, 4, 5, 6, 6, 4};
|
|
final int[] expectedFlows = {4, 4, 2, 0, 4, 4, 0, 6, 4};
|
|
final int expectedTotalFlow = 10;
|
|
StarGraph graph = new StarGraph(numNodes, numArcs);
|
|
MaxFlow maxFlow = new MaxFlow(graph, 0, numNodes - 1);
|
|
for (int i = 0; i < numArcs; ++i) {
|
|
final int arc = graph.addArc(tails[i], heads[i]);
|
|
maxFlow.setArcCapacity(arc, capacities[i]);
|
|
}
|
|
if (maxFlow.solve()) {
|
|
final long totalFlow = maxFlow.getOptimalFlow();
|
|
System.out.println("total flow " + totalFlow + "/" + expectedTotalFlow);
|
|
for (int i = 0; i < numArcs; ++i) {
|
|
System.out.println("Arc " + i + ": " + maxFlow.flow(i) + "/" +
|
|
expectedFlows[i]);
|
|
}
|
|
} else {
|
|
System.out.println("No solution found");
|
|
}
|
|
}
|
|
|
|
public static void main(String[] args) throws Exception {
|
|
FlowExample.solveMinCostFlow();
|
|
FlowExample.solveMaxFlow();
|
|
}
|
|
}
|