Avoid numerical errors during testing in vector tile factories (#74343)

elastic · Jun 23, 2021 · 592b61a · 592b61a
1 parent 0c11c64
commit 592b61a
Show file tree

Hide file tree

Showing 2 changed files with 38 additions and 6 deletions.
diff --git a/...r-tile/src/main/java/org/elasticsearch/xpack/vectortile/feature/SimpleFeatureFactory.java b/...r-tile/src/main/java/org/elasticsearch/xpack/vectortile/feature/SimpleFeatureFactory.java
@@ -21,14 +21,15 @@
 public class SimpleFeatureFactory {
 
     private final int extent;
-    private final Rectangle rectangle;
-    private final double pointXScale, pointYScale;
+    private final double pointXScale, pointYScale, pointXTranslate, pointYTranslate;
 
     public SimpleFeatureFactory(int z, int x, int y, int extent) {
         this.extent = extent;
-        rectangle = FeatureFactoryUtils.getTileBounds(z, x, y);
+        final Rectangle rectangle = FeatureFactoryUtils.getTileBounds(z, x, y);
         pointXScale = (double) extent / (rectangle.getMaxLon() - rectangle.getMinLon());
-        pointYScale = -(double) extent / (rectangle.getMaxLat() - rectangle.getMinLat());
+        pointYScale = (double) -extent / (rectangle.getMaxLat() - rectangle.getMinLat());
+        pointXTranslate = -pointXScale * rectangle.getMinX();
+        pointYTranslate = -pointYScale * rectangle.getMinY();
     }
 
     public void point(VectorTile.Tile.Feature.Builder featureBuilder, double lon, double lat) {
@@ -62,10 +63,10 @@ public void box(VectorTile.Tile.Feature.Builder featureBuilder, double minLon, d
     }
 
     private int lat(double lat) {
-        return (int) Math.round(pointYScale * (FeatureFactoryUtils.latToSphericalMercator(lat) - rectangle.getMinY())) + extent;
+        return (int) Math.round(pointYScale * FeatureFactoryUtils.latToSphericalMercator(lat) + pointYTranslate) + extent;
     }
 
     private int lon(double lon) {
-        return (int) Math.round(pointXScale * (FeatureFactoryUtils.lonToSphericalMercator(lon) - rectangle.getMinX()));
+        return (int) Math.round(pointXScale * FeatureFactoryUtils.lonToSphericalMercator(lon) + pointXTranslate);
     }
 }
diff --git a/...or-tile/src/test/java/org/elasticsearch/xpack/vectortile/feature/FeatureFactoryTests.java b/...or-tile/src/test/java/org/elasticsearch/xpack/vectortile/feature/FeatureFactoryTests.java
@@ -17,6 +17,7 @@
 import org.elasticsearch.test.ESTestCase;
 import org.hamcrest.Matchers;
 
+import java.util.Arrays;
 import java.util.List;
 
 public class FeatureFactoryTests extends ESTestCase {
@@ -26,6 +27,8 @@ public void testPoint() {
         int x = randomIntBetween(0, (1 << z) - 1);
         int y = randomIntBetween(0, (1 << z) - 1);
         int extent = randomIntBetween(1 << 8, 1 << 14);
+        // check if we might have numerical error due to floating point arithmetic
+        assumeFalse("", hasNumericalError(z, x, y, extent));
         Rectangle rectangle = GeoTileUtils.toBoundingBox(x, y, z);
         SimpleFeatureFactory builder = new SimpleFeatureFactory(z, x, y, extent);
         FeatureFactory factory = new FeatureFactory(z, x, y, extent);
@@ -44,6 +47,34 @@ public void testPoint() {
         }
     }
 
+    public void testIssue74341() {
+        int z = 1;
+        int x = 0;
+        int y = 0;
+        int extent = 1730;
+        // this is the typical case we need to guard from.
+        assertThat(hasNumericalError(z, x, y, extent), Matchers.equalTo(true));
+        double lon = -171.0;
+        double lat = 0.9999999403953552;
+        SimpleFeatureFactory builder = new SimpleFeatureFactory(z, x, y, extent);
+        FeatureFactory factory = new FeatureFactory(z, x, y, extent);
+        VectorTile.Tile.Feature.Builder featureBuilder = VectorTile.Tile.Feature.newBuilder();
+        builder.point(featureBuilder, lon, lat);
+        byte[] b1 = featureBuilder.build().toByteArray();
+        Point point = new Point(lon, lat);
+        List<VectorTile.Tile.Feature> features = factory.getFeatures(point, new UserDataIgnoreConverter());
+        assertThat(features.size(), Matchers.equalTo(1));
+        byte[] b2 = features.get(0).toByteArray();
+        assertThat(Arrays.equals(b1, b2), Matchers.equalTo(false));
+    }
+
+    private boolean hasNumericalError(int z, int x, int y, int extent) {
+        final Rectangle rectangle = FeatureFactoryUtils.getTileBounds(z, x, y);
+        final double xDiff = rectangle.getMaxLon() - rectangle.getMinLon();
+        final double yDiff = rectangle.getMaxLat() - rectangle.getMinLat();
+        return (double) -extent / yDiff != -1d / (yDiff / (double) extent) || (double) extent / xDiff != 1d / (xDiff / (double) extent);
+    }
+
     public void testRectangle() {
         int z = randomIntBetween(1, 10);
         int x = randomIntBetween(0, (1 << z) - 1);