chore: support TSPLIB95 datasets in the TSP example (#415)

Author: triceo

examples/src/main/java/ai/timefold/solver/examples/common/persistence/AbstractTxtSolutionImporter.java

@@ -356,7 +356,11 @@ public String[] splitBy(String line, String delimiterRegex, String delimiterName
                     }
                     lineTokenList.add(token);
                 }
-                lineTokens = lineTokenList.toArray(new String[0]);
+                // Empty token == somewhere in there was an extra empty space
+                lineTokens = lineTokenList
+                        .stream()
+                        .filter(token -> !token.isEmpty())
+                        .toArray(String[]::new);
             }
             if (minimumNumberOfTokens != null && lineTokens.length < minimumNumberOfTokens) {
                 throw new IllegalArgumentException("Read line (" + line + ") has " + lineTokens.length

examples/src/main/java/ai/timefold/solver/examples/tsp/domain/location/AirLocation.java

@@ -16,8 +16,7 @@ public AirLocation(long id, double latitude, double longitude) {
     @Override
     public long getDistanceTo(Location location) {
         double distance = getAirDistanceDoubleTo(location);
-        // Multiplied by 1000 to avoid floating point arithmetic rounding errors
-        return (long) (distance * 1000.0 + 0.5);
+        return adjust(distance);
     }
 
 }

examples/src/main/java/ai/timefold/solver/examples/tsp/domain/location/DistanceType.java

@@ -1,12 +1,23 @@
 package ai.timefold.solver.examples.tsp.domain.location;
 
 public enum DistanceType {
-    /**
-     * Requires that all {@link Location} instances are of type {@link AirLocation}.
-     */
-    AIR_DISTANCE,
-    /**
-     * Requires that all {@link Location} instances are of type {@link RoadLocation}.
-     */
-    ROAD_DISTANCE;
+    AIR_DISTANCE(AirLocation::new),
+    ROAD_DISTANCE(RoadLocation::new),
+    GEOGRAPHIC_DISTANCE(GeoLocation::new),
+    PSEUDO_ROAD_DISTANCE(PseudoRoadLocation::new); // Niche distance type for TSPLIB95.
+
+    private final LocationFunction locationFunction;
+
+    DistanceType(LocationFunction locationFunction) {
+        this.locationFunction = locationFunction;
+    }
+
+    public <Location_ extends Location> Location_ createLocation(long id, double x, double y) {
+        return (Location_) locationFunction.apply(id, x, y);
+    }
+
+    interface LocationFunction {
+        Location apply(long id, double x, double y);
+    }
+
 }

examples/src/main/java/ai/timefold/solver/examples/tsp/domain/location/GeoLocation.java

@@ -0,0 +1,32 @@
+package ai.timefold.solver.examples.tsp.domain.location;
+
+/**
+ * Used with {@link DistanceType#GEOGRAPHIC_DISTANCE}.
+ */
+public class GeoLocation extends Location {
+
+    private static final double PI = 3.141592;
+    private static final double RRR = 6378.388;
+
+    public GeoLocation() {
+    }
+
+    public GeoLocation(long id, double x, double y) {
+        super(id, toCoordinate(x), toCoordinate(y));
+    }
+
+    @Override
+    public long getDistanceTo(Location location) {
+        double q1 = Math.cos(location.longitude - longitude);
+        double q2 = Math.cos(location.latitude - latitude);
+        double q3 = Math.cos(location.latitude + latitude);
+        return adjust(RRR * Math.acos(0.5 * ((1.0 + q1) * q2 - (1.0 - q1) * q3)) + 1.0);
+    }
+
+    private static double toCoordinate(double i) {
+        long deg = adjust(i);
+        double min = i - deg;
+        return PI * (deg + 5.0 * min / 3.0) / 180.0;
+    }
+
+}

examples/src/main/java/ai/timefold/solver/examples/tsp/domain/location/Location.java

@@ -98,6 +98,10 @@ public double getAngle(Location location) {
         return Math.atan2(latitudeDifference, longitudeDifference);
     }
 
+    protected static long adjust(double distance) {
+        return (long) (distance + 0.5); // +0.5 to avoid floating point rounding errors
+    }
+
     @Override
     public String toString() {
         if (name == null) {

examples/src/main/java/ai/timefold/solver/examples/tsp/domain/location/PseudoRoadLocation.java

@@ -0,0 +1,21 @@
+package ai.timefold.solver.examples.tsp.domain.location;
+
+public class PseudoRoadLocation extends Location {
+
+    public PseudoRoadLocation() {
+    }
+
+    public PseudoRoadLocation(long id, double x, double y) {
+        super(id, x, y);
+    }
+
+    @Override
+    public long getDistanceTo(Location location) {
+        double xd = location.latitude - latitude;
+        double yd = location.longitude - longitude;
+        double rij = Math.sqrt((xd * xd + yd * yd) / 10.0);
+        long tij = adjust(rij);
+        return tij < rij ? tij + 1 : tij;
+    }
+
+}

examples/src/main/java/ai/timefold/solver/examples/tsp/domain/location/RoadLocation.java

@@ -43,9 +43,12 @@ public long getDistanceTo(Location location) {
         if (this == location) {
             return 0L;
         }
-        double distance = travelDistanceMap.get((RoadLocation) location);
-        // Multiplied by 1000 to avoid floating point arithmetic rounding errors
-        return (long) (distance * 1000.0 + 0.5);
+        Double distance = travelDistanceMap.get((RoadLocation) location);
+        if (distance == null) {
+            throw new IllegalStateException("The travelDistanceMap in location (%s) does not contain the key (%s)."
+                    .formatted(this, location));
+        }
+        return adjust(distance);
     }
 
 }

examples/src/main/java/ai/timefold/solver/examples/tsp/persistence/TspImageStipplerImporter.java

@@ -9,9 +9,7 @@
 import ai.timefold.solver.examples.common.persistence.AbstractPngSolutionImporter;
 import ai.timefold.solver.examples.common.persistence.SolutionConverter;
 import ai.timefold.solver.examples.tsp.app.TspApp;
-import ai.timefold.solver.examples.tsp.domain.Domicile;
 import ai.timefold.solver.examples.tsp.domain.TspSolution;
-import ai.timefold.solver.examples.tsp.domain.Visit;
 import ai.timefold.solver.examples.tsp.domain.location.AirLocation;
 import ai.timefold.solver.examples.tsp.domain.location.DistanceType;
 import ai.timefold.solver.examples.tsp.domain.location.Location;
@@ -98,21 +96,7 @@ private void floydSteinbergDithering() {
         }
 
         private void createVisitList() {
-            List<Location> locationList = tspSolution.getLocationList();
-            List<Visit> visitList = new ArrayList<>(locationList.size() - 1);
-            int count = 0;
-            for (Location location : locationList) {
-                if (count < 1) {
-                    Domicile domicile = new Domicile(location.getId(), location);
-                    tspSolution.setDomicile(domicile);
-                } else {
-                    Visit visit = new Visit(location.getId(), location);
-                    // Notice that we leave the PlanningVariable properties on null
-                    visitList.add(visit);
-                }
-                count++;
-            }
-            tspSolution.setVisitList(visitList);
+            TspImporter.TspInputBuilder.createVisitsFromLocations(tspSolution);
         }
 
     }