Add CoveragePolygonValidator section performance optimization (#1053)

modules/core/src/main/java/org/locationtech/jts/coverage/CoveragePolygon.java

@@ -0,0 +1,63 @@
+/*
+ * Copyright (c) 2022 Martin Davis.
+ *
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License 2.0
+ * and Eclipse Distribution License v. 1.0 which accompanies this distribution.
+ * The Eclipse Public License is available at http://www.eclipse.org/legal/epl-v20.html
+ * and the Eclipse Distribution License is available at
+ *
+ * http://www.eclipse.org/org/documents/edl-v10.php.
+ */
+package org.locationtech.jts.coverage;
+
+import org.locationtech.jts.algorithm.locate.IndexedPointInAreaLocator;
+import org.locationtech.jts.algorithm.locate.PointOnGeometryLocator;
+import org.locationtech.jts.geom.Coordinate;
+import org.locationtech.jts.geom.Envelope;
+import org.locationtech.jts.geom.Location;
+import org.locationtech.jts.geom.Polygon;
+
+class CoveragePolygon {
+
+  private Polygon polygon;
+  private Envelope polyEnv;
+  IndexedPointInAreaLocator locator;
+
+  public CoveragePolygon(Polygon poly) {
+    this.polygon = poly;
+    polyEnv = polygon.getEnvelopeInternal();
+  }
+
+  public boolean intersects(Envelope env) {
+    //-- test intersection explicitly to avoid expensive null check
+    //return polyEnv.intersects(env);
+    return ! (env.getMinX() > polyEnv.getMaxX()
+        || env.getMaxX() < polyEnv.getMinX()
+        || env.getMinY() > polyEnv.getMaxY()
+        || env.getMaxY() < polyEnv.getMinY());
+  }
+
+  public boolean contains(Coordinate p) {
+    //-- test intersection explicitly to avoid expensive null check
+    if (! intersects(p))
+      return false;
+    PointOnGeometryLocator pia = getLocator();
+    return Location.INTERIOR == pia.locate(p);    
+  }
+
+  private boolean intersects(Coordinate p) {
+    return ! (p.x > polyEnv.getMaxX() ||
+        p.x < polyEnv.getMinX() ||
+        p.y > polyEnv.getMaxY() ||
+        p.y < polyEnv.getMinY());
+  }
+
+  private PointOnGeometryLocator getLocator() {
+    if (locator == null) {
+      locator = new IndexedPointInAreaLocator(polygon);
+    }
+    return locator;
+  }
+
+}

modules/core/src/main/java/org/locationtech/jts/coverage/CoveragePolygonValidator.java

@@ -85,7 +85,7 @@
  *
  */
 public class CoveragePolygonValidator {
-  
+
   /**
    * Validates that a polygon is coverage-valid  against the
    * surrounding polygons in a polygonal coverage.
@@ -122,8 +122,7 @@ public static Geometry validate(Geometry targetPolygon, Geometry[] adjPolygons,
   private double gapWidth = 0.0;
   private GeometryFactory geomFactory;
   private Geometry[] adjGeoms;
-  private List<Polygon> adjPolygons;
-  private IndexedPointInAreaLocator[] adjPolygonLocators;
+  private List<CoveragePolygon> adjCovPolygons;
 
   /**
    * Create a new validator.
@@ -158,8 +157,8 @@ public void setGapWidth(double gapWidth) {
    * @return a linear geometry containing the segments causing invalidity (if any)
    */
   public Geometry validate() {
-    adjPolygons = extractPolygons(adjGeoms);
-    adjPolygonLocators = new IndexedPointInAreaLocator[adjPolygons.size()];
+    List<Polygon> adjPolygons = extractPolygons(adjGeoms);
+    adjCovPolygons = toCoveragePolygons(adjPolygons);
 
     List<CoverageRing> targetRings = CoverageRing.createRings(targetGeom);
     List<CoverageRing> adjRings = CoverageRing.createRings(adjPolygons);
@@ -177,6 +176,14 @@ public Geometry validate() {
     return createInvalidLines(targetRings);
   }
 
+  private List<CoveragePolygon> toCoveragePolygons(List<Polygon> polygons) {
+    List<CoveragePolygon> covPolys = new ArrayList<CoveragePolygon>();
+    for (Polygon poly : polygons) {
+      covPolys.add(new CoveragePolygon(poly));
+    }
+    return covPolys;
+  }
+
   private void checkTargetRings(List<CoverageRing> targetRings, List<CoverageRing> adjRings, Envelope targetEnv) {
     markMatchedSegments(targetRings, adjRings, targetEnv);
 
@@ -197,7 +204,8 @@ private void checkTargetRings(List<CoverageRing> targetRings, List<CoverageRing>
      * Do further checks to see if any of them are are invalid.
      */
     markInvalidInteractingSegments(targetRings, adjRings, gapWidth);
-    markInvalidInteriorSegments(targetRings, adjPolygons);
+    markInvalidInteriorSegments(targetRings, adjCovPolygons);
+    //OLDmarkInvalidInteriorSegments(targetRings, adjPolygons);
   }
 
   private static List<Polygon> extractPolygons(Geometry[] geoms) {
@@ -368,77 +376,79 @@ private void markInvalidInteractingSegments(List<CoverageRing> targetRings, List
     segSetMutInt.process(adjRings, detector);
   }
 
+  /**
+   * Stride is chosen experimentally to provide good performance
+   */
+  private static final int RING_SECTION_STRIDE = 1000;
+
   /**
    * Marks invalid target segments which are fully interior
    * to an adjacent polygon.
    * 
    * @param targetRings the rings with segments to test
-   * @param adjPolygons the adjacent polygons
+   * @param adjCovPolygons the adjacent polygons
    */
-  private void markInvalidInteriorSegments(List<CoverageRing> targetRings, List<Polygon> adjPolygons) {
+  private void markInvalidInteriorSegments(List<CoverageRing> targetRings, List<CoveragePolygon> adjCovPolygons) {
     for (CoverageRing ring : targetRings) {
-      for (int i = 0; i < ring.size() - 1; i++) {
-        //-- skip check for segments with known state. 
-        if (ring.isKnown(i))
-          continue;
+      int stride = RING_SECTION_STRIDE;
+      for (int i = 0; i < ring.size() - 1; i += stride) {
+        int iEnd = i + stride;
+        if (iEnd >= ring.size())
+          iEnd = ring.size() - 1;
 
-        /**
-         * Check if vertex is in interior of an adjacent polygon.
-         * If so, the segments on either side are in the interior.
-         * Mark them invalid, unless they are already matched.
-         */
-        Coordinate p = ring.getCoordinate(i);
-        if (isInteriorVertex(p, adjPolygons)) {
-          ring.markInvalid(i);
-          //-- previous segment may be interior (but may also be matched)
-          int iPrev = i == 0 ? ring.size() - 2 : i-1;
-          if (! ring.isKnown(iPrev))
-            ring.markInvalid(iPrev);
-        }
+        markInvalidInteriorSection(ring, i, iEnd, adjCovPolygons);
       }
     }
   }
-  
+
   /**
-   * Tests if a coordinate is in the interior of some adjacent polygon.
-   * Uses the cached Point-In-Polygon indexed locators, for performance.
+   * Marks invalid target segments in a section which are interior
+   * to an adjacent polygon.
+   * Processing a section at a time dramatically improves efficiency.
+   * Due to the coherent organization of polygon rings,
+   * sections usually have a high spatial locality.
+   * This means that sections typically intersect only a few or often no adjacent polygons.
+   * The section envelope can be computed and tested against adjacent polygon envelopes quickly.
+   * The section can be skipped entirely if it does not interact with any polygons. 
    * 
-   * @param p the coordinate to test
-   * @param adjPolygons the list of polygons
-   * @return true if the point is in the interior
+   * @param ring
+   * @param iStart
+   * @param iEnd 
+   * @param adjPolygons
    */
-  private boolean isInteriorVertex(Coordinate p, List<Polygon> adjPolygons) {
-    /**
-     * There should not be too many adjacent polygons, 
-     * and hopefully not too many segments with unknown status
-     * so a linear scan should not be too inefficient
-     */
-    //TODO: try a spatial index?
-    for (int i = 0; i < adjPolygons.size(); i++) {
-      Polygon adjPoly = adjPolygons.get(i);
-
-      if (polygonContainsPoint(i, adjPoly, p))
-        return true;
+  private void markInvalidInteriorSection(CoverageRing ring, int iStart, int iEnd, List<CoveragePolygon> adjPolygons) {
+    Envelope sectionEnv = ring.getEnvelope(iStart, iEnd);
+    //TODO: is it worth indexing polygons?
+    for (CoveragePolygon adjPoly : adjPolygons) {
+      if (adjPoly.intersects(sectionEnv)) {
+        //-- test vertices in section
+        for (int i = iStart; i < iEnd; i++) {
+          markInvalidInteriorSegment(ring, i, adjPoly);
+        }
+      }
     }
-    return false;
-  }
-
-  private boolean polygonContainsPoint(int index, Polygon poly, Coordinate pt) {
-    if (! poly.getEnvelopeInternal().intersects(pt))
-      return false;
-    PointOnGeometryLocator pia = getLocator(index, poly);
-    return Location.INTERIOR == pia.locate(pt);
   }
 
-  private PointOnGeometryLocator getLocator(int index, Polygon poly) {
-    IndexedPointInAreaLocator loc = adjPolygonLocators[index];
-    if (loc == null) {
-      loc = new IndexedPointInAreaLocator(poly);
-      adjPolygonLocators[index] = loc;
+  private void markInvalidInteriorSegment(CoverageRing ring, int i, CoveragePolygon adjPoly) {
+    //-- skip check for segments with known state. 
+    if (ring.isKnown(i))
+      return;
+
+    /**
+     * Check if vertex is in interior of an adjacent polygon.
+     * If so, the segments on either side are in the interior.
+     * Mark them invalid, unless they are already matched.
+     */
+    Coordinate p = ring.getCoordinate(i);
+    if (adjPoly.contains(p)) {
+      ring.markInvalid(i);
+      //-- previous segment may be interior (but may also be matched)
+      int iPrev = i == 0 ? ring.size() - 2 : i-1;
+      if (! ring.isKnown(iPrev))
+        ring.markInvalid(iPrev);
     }
-    return loc;
   }
-
+  
   private Geometry createInvalidLines(List<CoverageRing> rings) {
     List<LineString> lines = new ArrayList<LineString>();
     for (CoverageRing ring : rings) {

modules/core/src/main/java/org/locationtech/jts/coverage/CoverageRing.java

@@ -17,6 +17,7 @@
 import org.locationtech.jts.algorithm.Orientation;
 import org.locationtech.jts.geom.Coordinate;
 import org.locationtech.jts.geom.CoordinateArrays;
+import org.locationtech.jts.geom.Envelope;
 import org.locationtech.jts.geom.Geometry;
 import org.locationtech.jts.geom.GeometryFactory;
 import org.locationtech.jts.geom.LineString;
@@ -92,6 +93,14 @@ private CoverageRing(Coordinate[] pts, boolean isInteriorOnRight) {
     isMatched = new boolean[size() - 1];
   }
 
+  public Envelope getEnvelope(int start, int end) {
+    Envelope env = new Envelope();
+    for (int i = start; i < end; i++) {
+      env.expandToInclude(getCoordinate(i));
+    }
+    return env;
+  }
+
   /**
    * Reports if the ring has canonical orientation,
    * with the polygon interior on the right (shell is CW).