The checkEdgeCrossings() method now uses the edge index of the context loop, instead of iterating over the product of all edges against all other edges filtered only by bounding volume. This method is integral to the performance of intersects(), contains(), containsOrCrosses(), etc. This matches the c++ algorithm in the corresponding method S2Loop::AreBoundariesCrossing.

-------------
Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=24938116

Author: eengle

src/com/google/common/geometry/S2Loop.java

@@ -894,66 +894,29 @@ private int findVertex(S2Point p) {
    * intersection tests. It is used in three slightly different variations to
    * implement contains(), intersects(), and containsOrCrosses().
    *
-   *  In a nutshell, this method checks all the edges of this polygon (A) for
+   *  In a nutshell, this method checks all the edges of this loop (A) for
    * intersection with all the edges of B. It returns -1 immediately if any edge
    * intersections are found. Otherwise, if there are any shared vertices, it
    * returns the minimum value of the given WedgeRelation for all such vertices
    * (returning immediately if any wedge returns -1). Returns +1 if there are no
    * intersections and no shared vertices.
    */
   private int checkEdgeCrossings(S2Loop b, S2EdgeUtil.WedgeRelation relation) {
-    if (b.numVertices() <= 6) {
-      int result = 1;
-      // For small loops (such as S2Cell boundaries), it is not worth computing
-      // longitude bounds to avoid edge tests, and it is more efficient to
-      // reverse the loop nesting.
-      for (int j = 0; j < b.numVertices(); ++j) {
-        S2EdgeUtil.EdgeCrosser crosser =
-            new S2EdgeUtil.EdgeCrosser(b.vertex(j), b.vertex(j + 1), vertex(0));
-        for (int i = 0; i < numVertices(); ++i) {
-          int crossing = crosser.robustCrossing(vertex(i + 1));
-          if (crossing < 0) {
-            continue;
-          }
-          if (crossing > 0) {
-            return -1; // There is a proper edge crossing.
-          }
-          // We only need to check each shared vertex once, so we only
-          // consider the case where vertex(i+1) == b->vertex(j+1).
-          if (vertex(i + 1).equals(b.vertex(j + 1))) {
-            result = Math.min(result, relation.test(
-                vertex(i), vertex(i + 1), vertex(i + 2), b.vertex(j), b.vertex(j + 2)));
-
-            if (result < 0) {
-              return result;
-            }
-          }
-        }
-      }
-      return result;
-    }
-
-    // For larger loops, we can save a lot of edge tests by first checking
-    // whether each edge of the outer loop intersects the xyz bounding
-    // box of the inner loop. To that end we now accumulate a bounding box
-    // in XYZ space for the inner loop.
-    S2EdgeUtil.XYZPruner pruner = new S2EdgeUtil.XYZPruner();
-    for (int i = 1; i < b.numVertices(); i++) {
-      pruner.addEdgeToBounds(b.vertex(i - 1), b.vertex(i));
-    }
-    pruner.addEdgeToBounds(b.vertex(b.numVertices() - 1), b.vertex(0));
-
-    pruner.setFirstIntersectPoint(vertex(0));
-
+    DataEdgeIterator it = getEdgeIterator(b.numVertices);
     int result = 1;
-    for (int i = 0; i < numVertices(); ++i) {
-      if (!pruner.intersects(vertex(i + 1))) {
-        continue;
-      }
+    // since 'this' usually has many more vertices than 'b', use the index on
+    // 'this' and loop over 'b'
+    for (int j = 0; j < b.numVertices(); ++j) {
       S2EdgeUtil.EdgeCrosser crosser =
-          new S2EdgeUtil.EdgeCrosser(vertex(i), vertex(i + 1), b.vertex(0));
-      for (int j = 0; j < b.numVertices(); ++j) {
-        int crossing = crosser.robustCrossing(b.vertex(j + 1));
+        new S2EdgeUtil.EdgeCrosser(b.vertex(j), b.vertex(j + 1), vertex(0));
+      int previousIndex = -2;
+      for (it.getCandidates(b.vertex(j), b.vertex(j + 1)); it.hasNext(); it.next()) {
+        int i = it.index();
+        if (previousIndex != i - 1) {
+          crosser.restartAt(vertex(i));
+        }
+        previousIndex = i;
+        int crossing = crosser.robustCrossing(vertex(i + 1));
         if (crossing < 0) {
           continue;
         }