Add DistanceOp optimization for Point-Point (#1049)

modules/core/src/main/java/org/locationtech/jts/operation/distance/DistanceOp.java

@@ -158,6 +158,11 @@ public double distance()
   	if (geom[0].isEmpty() || geom[1].isEmpty()) 
   		return 0.0;
 
+  	//-- optimization for Point/Point case
+  	if (geom[0] instanceof Point && geom[1] instanceof Point) {
+  	  return geom[0].getCoordinate().distance(geom[1].getCoordinate());
+  	}
+
     computeMinDistance();
     return minDistance;
   }

modules/core/src/test/java/test/jts/perf/operation/distance/PointPointDistancePerfTest.java

@@ -0,0 +1,61 @@
+package test.jts.perf.operation.distance;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import org.locationtech.jts.geom.Coordinate;
+import org.locationtech.jts.geom.Envelope;
+import org.locationtech.jts.geom.Geometry;
+import org.locationtech.jts.geom.GeometryFactory;
+import org.locationtech.jts.geom.Point;
+
+import test.jts.perf.PerformanceTestCase;
+import test.jts.perf.PerformanceTestRunner;
+
+public class PointPointDistancePerfTest extends PerformanceTestCase {
+
+
+  public static void main(String args[]) {
+    PerformanceTestRunner.run(PointPointDistancePerfTest.class);
+  }
+
+  private Point[] grid;
+
+  public PointPointDistancePerfTest(String name) {
+    super(name);
+    setRunSize(new int[] {10000});
+    setRunIterations(1);
+  }
+
+  public void startRun(int npts)
+  {
+    System.out.println("\n-------  Running with # pts = " + npts);
+    grid = createPointGrid(new Envelope(0, 10., 0, 10), npts);
+  }
+
+  private Point[] createPointGrid(Envelope envelope, int npts) {
+    List<Point> geoms = new ArrayList<Point>();
+    GeometryFactory fact = new GeometryFactory();
+    int nSide = (int) Math.sqrt(npts);
+    double xInc = envelope.getWidth() / nSide;
+    double yInc = envelope.getHeight() / nSide;
+    for (int i = 0; i < nSide; i++) {
+      for (int j = 0; j < nSide; j++) {
+        double x = envelope.getMinX() + i * xInc;
+        double y = envelope.getMinY() + i * yInc;
+        Point p = fact.createPoint(new Coordinate(x, y));
+        geoms.add(p);
+      }
+    }
+    return GeometryFactory.toPointArray(geoms);
+  }
+
+  public void runPoints() {
+    for (Geometry p1 : grid) {
+      for (Geometry p2 : grid) {
+        double dist = p1.distance(p2);
+      }
+    }
+  }
+
+}