Add Visvalingam Whyatt Simplifier (#1109)

planetiler-benchmarks/src/main/java/com/onthegomap/planetiler/benchmarks/BenchmarkSimplify.java

@@ -0,0 +1,84 @@
+package com.onthegomap.planetiler.benchmarks;
+
+import com.onthegomap.planetiler.geo.DouglasPeuckerSimplifier;
+import com.onthegomap.planetiler.geo.VWSimplifier;
+import com.onthegomap.planetiler.util.Format;
+import com.onthegomap.planetiler.util.FunctionThatThrows;
+import java.math.BigDecimal;
+import java.math.MathContext;
+import java.time.Duration;
+import org.locationtech.jts.geom.CoordinateXY;
+import org.locationtech.jts.geom.Geometry;
+import org.locationtech.jts.util.GeometricShapeFactory;
+
+public class BenchmarkSimplify {
+  private static int numLines;
+
+  public static void main(String[] args) throws Exception {
+    for (int i = 0; i < 10; i++) {
+      time("    DP(0.1)", geom -> DouglasPeuckerSimplifier.simplify(geom, 0.1));
+      time("      DP(1)", geom -> DouglasPeuckerSimplifier.simplify(geom, 1));
+      time("     DP(20)", geom -> DouglasPeuckerSimplifier.simplify(geom, 20));
+      time("  JTS VW(0)", geom -> org.locationtech.jts.simplify.VWSimplifier.simplify(geom, 0.01));
+      time("JTS VW(0.1)", geom -> org.locationtech.jts.simplify.VWSimplifier.simplify(geom, 0.1));
+      time("  JTS VW(1)", geom -> org.locationtech.jts.simplify.VWSimplifier.simplify(geom, 1));
+      time(" JTS VW(20)", geom -> org.locationtech.jts.simplify.VWSimplifier.simplify(geom, 20));
+      time("      VW(0)", geom -> new VWSimplifier().setTolerance(0).setWeight(0.7).transform(geom));
+      time("    VW(0.1)", geom -> new VWSimplifier().setTolerance(0.1).setWeight(0.7).transform(geom));
+      time("      VW(1)", geom -> new VWSimplifier().setTolerance(1).setWeight(0.7).transform(geom));
+      time("     VW(20)", geom -> new VWSimplifier().setTolerance(20).setWeight(0.7).transform(geom));
+    }
+    System.err.println(numLines);
+  }
+
+  private static void time(String name, FunctionThatThrows<Geometry, Geometry> fn) throws Exception {
+    System.err.println(String.join("\t",
+      name,
+      timePerSec(makeLines(2), fn),
+      timePerSec(makeLines(10), fn),
+      timePerSec(makeLines(50), fn),
+      timePerSec(makeLines(100), fn),
+      timePerSec(makeLines(10_000), fn)
+    ));
+  }
+
+  private static String timePerSec(Geometry geometry, FunctionThatThrows<Geometry, Geometry> fn)
+    throws Exception {
+    long start = System.nanoTime();
+    long end = start + Duration.ofSeconds(1).toNanos();
+    int num = 0;
+    boolean first = true;
+    for (; System.nanoTime() < end;) {
+      numLines += fn.apply(geometry).getNumPoints();
+      if (first) {
+        first = false;
+      }
+      num++;
+    }
+    return Format.defaultInstance()
+      .numeric(Math.round(num * 1d / ((System.nanoTime() - start) * 1d / Duration.ofSeconds(1).toNanos())), true);
+  }
+
+  private static String timeMillis(Geometry geometry, FunctionThatThrows<Geometry, Geometry> fn)
+    throws Exception {
+    long start = System.nanoTime();
+    long end = start + Duration.ofSeconds(1).toNanos();
+    int num = 0;
+    for (; System.nanoTime() < end;) {
+      numLines += fn.apply(geometry).getNumPoints();
+      num++;
+    }
+    // equivalent of toPrecision(3)
+    long nanosPer = (System.nanoTime() - start) / num;
+    var bd = new BigDecimal(nanosPer, new MathContext(3));
+    return Format.padRight(Duration.ofNanos(bd.longValue()).toString().replace("PT", ""), 6);
+  }
+
+  private static Geometry makeLines(int parts) {
+    var shapeFactory = new GeometricShapeFactory();
+    shapeFactory.setNumPoints(parts);
+    shapeFactory.setCentre(new CoordinateXY(0, 0));
+    shapeFactory.setSize(10);
+    return shapeFactory.createCircle();
+  }
+}

planetiler-core/src/main/java/com/onthegomap/planetiler/FeatureCollector.java

@@ -6,6 +6,7 @@
 import com.onthegomap.planetiler.geo.GeoUtils;
 import com.onthegomap.planetiler.geo.GeometryException;
 import com.onthegomap.planetiler.geo.GeometryType;
+import com.onthegomap.planetiler.geo.SimplifyMethod;
 import com.onthegomap.planetiler.reader.SourceFeature;
 import com.onthegomap.planetiler.reader.Struct;
 import com.onthegomap.planetiler.render.FeatureRenderer;
@@ -502,6 +503,9 @@ public final class Feature implements WithZoomRange<Feature>, WithAttrs<Feature>
     private double pixelToleranceAtMaxZoom = config.simplifyToleranceAtMaxZoom();
     private ZoomFunction<Number> pixelTolerance = null;
 
+    private SimplifyMethod defaultSimplifyMethod = SimplifyMethod.DOUGLAS_PEUCKER;
+    private ZoomFunction<SimplifyMethod> simplifyMethod = null;
+
     private String numPointsAttr = null;
     private List<OverrideCommand> partialOverrides = null;
 
@@ -714,6 +718,28 @@ public double getPixelToleranceAtZoom(int zoom) {
         ZoomFunction.applyAsDoubleOrElse(pixelTolerance, zoom, defaultPixelTolerance);
     }
 
+    /**
+     * Sets the fallback line and polygon simplify method when not overriden by *
+     * {@link #setSimplifyMethodOverrides(ZoomFunction)}.
+     */
+    public FeatureCollector.Feature setSimplifyMethod(SimplifyMethod strategy) {
+      defaultSimplifyMethod = strategy;
+      return this;
+    }
+
+    /** Set simplification algorithm to use at different zoom levels. */
+    public FeatureCollector.Feature setSimplifyMethodOverrides(ZoomFunction<SimplifyMethod> overrides) {
+      simplifyMethod = overrides;
+      return this;
+    }
+
+    /**
+     * Returns the simplification method for lines and polygons in tile pixels at {@code zoom}.
+     */
+    public SimplifyMethod getSimplifyMethodAtZoom(int zoom) {
+      return ZoomFunction.applyOrElse(simplifyMethod, zoom, defaultSimplifyMethod);
+    }
+
     /**
      * Sets the simplification tolerance for lines and polygons in tile pixels below the maximum zoom-level of the map.
      * <p>

planetiler-core/src/main/java/com/onthegomap/planetiler/collection/ArrayDoubleMinHeap.java

@@ -0,0 +1,229 @@
+package com.onthegomap.planetiler.collection;
+
+import java.util.Arrays;
+import java.util.function.IntBinaryOperator;
+
+/**
+ * A min-heap stored in an array where each element has 4 children.
+ * <p>
+ * This is about 5-10% faster than the standard binary min-heap for the case of merging sorted lists.
+ * <p>
+ * Ported from <a href=
+ * "https://github.com/graphhopper/graphhopper/blob/master/core/src/main/java/com/graphhopper/coll/MinHeapWithUpdate.java">GraphHopper</a>
+ * and:
+ * <ul>
+ * <li>modified to use {@code double} values instead of {@code float}</li>
+ * <li>extracted a common interface for subclass implementations</li>
+ * <li>modified so that each element has 4 children instead of 2 (improves performance by 5-10%)</li>
+ * <li>performance improvements to minimize array lookups</li>
+ * </ul>
+ *
+ * @see <a href="https://en.wikipedia.org/wiki/D-ary_heap">d-ary heap (wikipedia)</a>
+ */
+class ArrayDoubleMinHeap implements DoubleMinHeap {
+  protected static final int NOT_PRESENT = -1;
+  protected final int[] posToId;
+  protected final int[] idToPos;
+  protected final double[] posToValue;
+  protected final int max;
+  protected int size;
+  private final IntBinaryOperator tieBreaker;
+
+  /**
+   * @param elements the number of elements that can be stored in this heap. Currently the heap cannot be resized or
+   *                 shrunk/trimmed after initial creation. elements-1 is the maximum id that can be stored in this heap
+   */
+  ArrayDoubleMinHeap(int elements, IntBinaryOperator tieBreaker) {
+    // we use an offset of one to make the arithmetic a bit simpler/more efficient, the 0th elements are not used!
+    posToId = new int[elements + 1];
+    idToPos = new int[elements + 1];
+    Arrays.fill(idToPos, NOT_PRESENT);
+    posToValue = new double[elements + 1];
+    posToValue[0] = Double.NEGATIVE_INFINITY;
+    this.max = elements;
+    this.tieBreaker = tieBreaker;
+  }
+
+  private static int firstChild(int index) {
+    return (index << 2) - 2;
+  }
+
+  private static int parent(int index) {
+    return (index + 2) >> 2;
+  }
+
+  @Override
+  public int size() {
+    return size;
+  }
+
+  @Override
+  public boolean isEmpty() {
+    return size == 0;
+  }
+
+  @Override
+  public void push(int id, double value) {
+    checkIdInRange(id);
+    if (size == max) {
+      throw new IllegalStateException("Cannot push anymore, the heap is already full. size: " + size);
+    }
+    if (contains(id)) {
+      throw new IllegalStateException("Element with id: " + id +
+        " was pushed already, you need to use the update method if you want to change its value");
+    }
+    size++;
+    posToId[size] = id;
+    idToPos[id] = size;
+    posToValue[size] = value;
+    percolateUp(size);
+  }
+
+  @Override
+  public boolean contains(int id) {
+    checkIdInRange(id);
+    return idToPos[id] != NOT_PRESENT;
+  }
+
+  @Override
+  public void update(int id, double value) {
+    checkIdInRange(id);
+    int pos = idToPos[id];
+    if (pos < 0) {
+      throw new IllegalStateException(
+        "The heap does not contain: " + id + ". Use the contains method to check this before calling update");
+    }
+    double prev = posToValue[pos];
+    posToValue[pos] = value;
+    int cmp = compareIdPos(value, prev, id, pos);
+    if (cmp > 0) {
+      percolateDown(pos);
+    } else if (cmp < 0) {
+      percolateUp(pos);
+    }
+  }
+
+  @Override
+  public void updateHead(double value) {
+    posToValue[1] = value;
+    percolateDown(1);
+  }
+
+  @Override
+  public int peekId() {
+    return posToId[1];
+  }
+
+  @Override
+  public double peekValue() {
+    return posToValue[1];
+  }
+
+  @Override
+  public int poll() {
+    int id = peekId();
+    posToId[1] = posToId[size];
+    posToValue[1] = posToValue[size];
+    idToPos[posToId[1]] = 1;
+    idToPos[id] = NOT_PRESENT;
+    size--;
+    percolateDown(1);
+    return id;
+  }
+
+  @Override
+  public void clear() {
+    for (int i = 1; i <= size; i++) {
+      idToPos[posToId[i]] = NOT_PRESENT;
+    }
+    size = 0;
+  }
+
+  private void percolateUp(int pos) {
+    assert pos != 0;
+    if (pos == 1) {
+      return;
+    }
+    final int id = posToId[pos];
+    final double val = posToValue[pos];
+    // the finish condition (index==0) is covered here automatically because we set vals[0]=-inf
+    int parent;
+    double parentValue;
+    while (compareIdPos(val, parentValue = posToValue[parent = parent(pos)], id, parent) < 0) {
+      posToValue[pos] = parentValue;
+      idToPos[posToId[pos] = posToId[parent]] = pos;
+      pos = parent;
+    }
+    posToId[pos] = id;
+    posToValue[pos] = val;
+    idToPos[posToId[pos]] = pos;
+  }
+
+  private void checkIdInRange(int id) {
+    if (id < 0 || id >= max) {
+      throw new IllegalArgumentException("Illegal id: " + id + ", legal range: [0, " + max + "[");
+    }
+  }
+
+  private void percolateDown(int pos) {
+    if (size == 0) {
+      return;
+    }
+    assert pos > 0;
+    assert pos <= size;
+    final int id = posToId[pos];
+    final double value = posToValue[pos];
+    int child;
+    while ((child = firstChild(pos)) <= size) {
+      // optimization: this is a very hot code path for performance of k-way merging,
+      // so manually-unroll the loop over the 4 child elements to find the minimum value
+      int minChild = child;
+      double minValue = posToValue[child], childValue;
+      if (++child <= size) {
+        if (comparePosPos(childValue = posToValue[child], minValue, child, minChild) < 0) {
+          minChild = child;
+          minValue = childValue;
+        }
+        if (++child <= size) {
+          if (comparePosPos(childValue = posToValue[child], minValue, child, minChild) < 0) {
+            minChild = child;
+            minValue = childValue;
+          }
+          if (++child <= size &&
+            comparePosPos(childValue = posToValue[child], minValue, child, minChild) < 0) {
+            minChild = child;
+            minValue = childValue;
+          }
+        }
+      }
+      if (compareIdPos(value, minValue, id, minChild) <= 0) {
+        break;
+      }
+      posToValue[pos] = minValue;
+      idToPos[posToId[pos] = posToId[minChild]] = pos;
+      pos = minChild;
+    }
+    posToId[pos] = id;
+    posToValue[pos] = value;
+    idToPos[id] = pos;
+  }
+
+  private int comparePosPos(double val1, double val2, int pos1, int pos2) {
+    if (val1 < val2) {
+      return -1;
+    } else if (val1 == val2 && val1 != Double.NEGATIVE_INFINITY) {
+      return tieBreaker.applyAsInt(posToId[pos1], posToId[pos2]);
+    }
+    return 1;
+  }
+
+  private int compareIdPos(double val1, double val2, int id1, int pos2) {
+    if (val1 < val2) {
+      return -1;
+    } else if (val1 == val2 && val1 != Double.NEGATIVE_INFINITY) {
+      return tieBreaker.applyAsInt(id1, posToId[pos2]);
+    }
+    return 1;
+  }
+
+}