From dacc15f4bac833144aa46cb125796f3c69905524 Mon Sep 17 00:00:00 2001
From: Schankula Christopher <schankuc@mcmaster.ca>
Date: Sun, 1 Apr 2018 17:18:03 -0400
Subject: [PATCH] clean up KDT
---
src/sort/KDT.java | 115 ++++++++++++----------------------------------
1 file changed, 29 insertions(+), 86 deletions(-)
diff --git a/src/sort/KDT.java b/src/sort/KDT.java
index 1ee1043..242a5af 100644
--- a/src/sort/KDT.java
+++ b/src/sort/KDT.java
@@ -8,7 +8,7 @@ import java.io.ObjectOutputStream;
import java.io.Serializable;
import java.util.ArrayList;
-import sandbox.Point;
+import org.hamcrest.core.IsInstanceOf;
/**
* A class for constructing KD-trees with range-searching abilities. Written using
@@ -31,55 +31,8 @@ public class KDT<KeyVal extends Comparable<KeyVal>> implements Serializable {
/**
*
*/
- KDNode root;
- ArrayList<GeneralCompare<KeyVal>> axes;
-
- public static void main(String[] args) {
- GeneralCompare<Point> compX = (p1, p2) -> (int) ((Point) p1).getX() - (int) ((Point) p2).getX();
- GeneralCompare<Point> compY = (p1, p2) -> (int) ((Point) p1).getY() - (int) ((Point) p2).getY();
-
- //(2,3), (4,7), (5,4), (7,2), (8,1), (9,6)
- //(8,1), (7,2), (2,3), (5,4), (9,6), (4,7)
- Point p1 = new Point(2,3);
- Point p2 = new Point(5,4);
- Point p3 = new Point(9,6);
- Point p4 = new Point(4,7);
- Point p5 = new Point(8,1);
- Point p6 = new Point(7,2);
-
- ArrayList<GeneralCompare<Point>> axes = new ArrayList<GeneralCompare<Point>>();
- axes.add(compX);
- axes.add(compY);
-
- Point[] pts = {p1, p2, p3, p4, p5, p6};
-
- //KDT<Point> kdt = new KDT<Point>(axes, pts);
- KDT<Point> kdt = new KDT<Point>("kdtree.ser");
- System.out.println(kdt.size());
- System.out.println(kdt.height());
-
- //GeneralRange<Point> xRange = p -> 4 <= p.getX() && p.getX() <= 6;
- //GeneralRange<Point> yRange = p -> 3 <= p.getY() && p.getY() <= 5;
-
- GeneralRange<Point> xRange = p -> p.getX() < 2 ? -1 : (p.getX() > 7 ? 1 : 0);
- GeneralRange<Point> yRange = p -> 0;//p.getY() < 3 ? -1 : (p.getY() > 6 ? 1 : 0);
-
-
- ArrayList<GeneralRange<Point>> ranges = new ArrayList<GeneralRange<Point>>();
- ranges.add(xRange);
- ranges.add(yRange);
-
- Iterable<Point> results = kdt.rangeSearch(ranges);
-
- System.out.println("Results");
- for (Point p : results) {
- System.out.println(p);
- }
-
- System.out.println(kdt.toString());
-
- kdt.writeToFile("kdtree.ser");
- }
+ private KDNode root;
+ private ArrayList<GeneralCompare<KeyVal>> axes;
/**
* A node in a serializable KD-tree.
@@ -144,6 +97,16 @@ public class KDT<KeyVal extends Comparable<KeyVal>> implements Serializable {
root = buildTree(keyvals, 0, keyvals.length - 1, 0);
}
+ /**
+ * Builds a balanced tree recursively. Builds the tree by using the (i % k)th comparison
+ * function on each level i of the tree.
+ *
+ * @param keyvals The array of key-value objects
+ * @param lo The lower bound of the part to build
+ * @param hi The upper bound of the part to build
+ * @param depth The depth of the new node to be created
+ * @return The new node
+ */
private KDNode buildTree(Comparable<KeyVal>[] keyvals, int lo, int hi, int depth) {
if (lo > hi) return null;
int axis = depth % getK();
@@ -166,7 +129,10 @@ public class KDT<KeyVal extends Comparable<KeyVal>> implements Serializable {
* @param range An ArrayList of GeneralRange instances. This must take a value of type
* KeyVal and return whether that value is in the range for the given axis. Must provide
* an ArrayList with a size equal to the current tree's number of axes, k.
- * @return An Iterable of nodes found to be matchign the range search.
+ *
+ * The search works by traversing the tree as in a BST but only comparing the (i % k)th
+ * axis on each level i of the tree.
+ * @return An Iterable of nodes found to be matching the range search.
*/
public Iterable<KeyVal> rangeSearch(ArrayList<GeneralRange<KeyVal>> range){
ArrayList<KeyVal> result = new ArrayList<KeyVal>();
@@ -174,6 +140,7 @@ public class KDT<KeyVal extends Comparable<KeyVal>> implements Serializable {
return result;
}
+ //recursive private range search function
private void rangeSearch(KDNode x, ArrayList<GeneralRange<KeyVal>> range, ArrayList<KeyVal> result, int depth) {
if (x == null) return;
int axis = depth % getK();
@@ -182,21 +149,29 @@ public class KDT<KeyVal extends Comparable<KeyVal>> implements Serializable {
//System.out.println("Try: " + x.keyval);
int bounds = rg.isInBounds((KeyVal) x.keyval);
+ //if it's in the bounds, must search both subtrees. Also a candidate to be included in the results
if (bounds == 0) {
- //System.out.println(pointInside(x.keyval, range));
+ //if the point is inside the axis range, check if it's in the other ranges too
if (pointInside(x.keyval, range)) {
result.add(x.keyval);
}
+ //range search both subtrees
rangeSearch(x.left, range, result, depth + 1);
rangeSearch(x.right, range, result, depth + 1);
- } else if (bounds > 0) {
+ } else if (bounds > 0) { //if it's bigger than the current axis, search the left subtree
rangeSearch(x.left, range, result, depth + 1);
- } else if (bounds < 0)
+ } else if (bounds < 0) //if it's smaller than the current axis, search the right subtree
rangeSearch(x.right, range, result, depth + 1);
return;
}
+ /**
+ * See if a point is inside the range given for all axes
+ * @param pt The point to test
+ * @param range The range search for all axes
+ * @return true if inside all ranges, false otherwise
+ */
private boolean pointInside(KeyVal pt, ArrayList<GeneralRange<KeyVal>> range) {
for (int i = 0; i < axes.size(); i++)
if (range.get(i).isInBounds(pt) != 0) return false;
@@ -236,36 +211,4 @@ public class KDT<KeyVal extends Comparable<KeyVal>> implements Serializable {
public int getK() {
return axes.size();
}
-
- /**
- * Generates and returns a string representation of the nodes in the kd-tree.
- * Note: for large trees, this may be slow and unstable.
- * @return a string representation of the nodes in the kd-tree.
- */
- public String toString() {
- return toString(root, "");
- }
-
- private String toString(KDNode x, String depth) {
- if (x == null) return depth + "null\n";
- String result = "";
- result += depth + x.keyval.toString() + "\n";
- result += toString(x.left, depth + " ");
- result += toString(x.right, depth + " ");
- return result;
- }
-
- public void writeToFile(String fn) {
- try {
- FileOutputStream fileOut =
- new FileOutputStream(fn);
- ObjectOutputStream out = new ObjectOutputStream(fileOut);
- out.writeObject(this);
- out.close();
- fileOut.close();
- System.out.printf("Serialized data is saved in /tmp/kdtree.ser");
- } catch (IOException i) {
- i.printStackTrace();
- }
- }
}
--
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