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fix a* implementation by adding decrease-key operation to heap implementations

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This commit is contained in:
Leijurv 2018-08-05 11:30:50 -04:00
parent 3072142513
commit 8ee641f310
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8 changed files with 141 additions and 35 deletions
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9
src/main/java/baritone/bot/pathing/calc/AStarPathFinder.java
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@ -1,8 +1,5 @@
package baritone.bot.pathing.calc;
//import baritone.Baritone;
import baritone.bot.pathing.calc.openset.BinaryHeapOpenSet;
import baritone.bot.pathing.calc.openset.IOpenSet;
import baritone.bot.pathing.goals.Goal;
@ -55,8 +52,8 @@ public class AStarPathFinder extends AbstractNodeCostSearch {
}
}*/
PathNode currentNode = openSet.removeLowest();
mostRecentConsidered = currentNode;
currentNode.isOpen = false;
mostRecentConsidered = currentNode;
BlockPos currentNodePos = currentNode.pos;
numNodes++;
if (System.currentTimeMillis() > lastPrintout + 1000) {//print once a second
@ -92,7 +89,9 @@ public class AStarPathFinder extends AbstractNodeCostSearch {
neighbor.previousMovement = movementToGetToNeighbor;
neighbor.cost = tentativeCost;
neighbor.combinedCost = tentativeCost + neighbor.estimatedCostToGoal;
if (!neighbor.isOpen) {
if (neighbor.isOpen) {
openSet.update(neighbor);
} else {
openSet.insert(neighbor);//dont double count, dont insert into open set if it's already there
neighbor.isOpen = true;
}

4
src/main/java/baritone/bot/pathing/calc/PathNode.java
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@ -2,6 +2,7 @@ package baritone.bot.pathing.calc;
import baritone.bot.pathing.goals.Goal;
import baritone.bot.pathing.movement.Movement;
import baritone.bot.pathing.util.FibonacciHeap;
import net.minecraft.util.math.BlockPos;
import java.util.Objects;
@ -58,6 +59,9 @@ public class PathNode {
*/
boolean isOpen;
public int heapPosition;
public FibonacciHeap.Node parent;
public PathNode(BlockPos pos, Goal goal) {
this.pos = pos;
this.previous = null;

39
src/main/java/baritone/bot/pathing/calc/openset/BinaryHeapOpenSet.java
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@ -37,13 +37,13 @@ public class BinaryHeapOpenSet implements IOpenSet {
}
size++;
int index = size;
value.heapPosition = index;
array[index] = value;
int parent = index >>> 1;
while (index > 1 && array[parent].combinedCost > array[index].combinedCost) {
swap(index, parent);
index = parent;
parent = index >>> 1;
upHeap(index);
}
public void update(PathNode node) {
upHeap(node.heapPosition);
}
@Override
@ -58,24 +58,37 @@ public class BinaryHeapOpenSet implements IOpenSet {
}
PathNode result = array[1];
array[1] = array[size];
array[1].heapPosition = 1;
array[size] = null;
size--;
int index = 1;
downHeap(1);
result.heapPosition = -1;
return result;
}
private void upHeap(int index) {
int parent = index >>> 1;
while (index > 1 && array[parent].combinedCost > array[index].combinedCost) {
swap(index, parent);
index = parent;
parent = index >>> 1;
}
}
private void downHeap(int index) {
int smallerChild = 2;
while (smallerChild <= size) {
int right = smallerChild + 1;
if (right <= size && array[smallerChild].combinedCost > array[right].combinedCost) {
smallerChild = right;
}
if (array[index].combinedCost > array[smallerChild].combinedCost) {
swap(index, smallerChild);
} else {
if (array[index].combinedCost <= array[smallerChild].combinedCost) {
break;
}
swap(index, smallerChild);
index = smallerChild;
smallerChild = index << 1;
}
return result;
}
/**
@ -85,8 +98,14 @@ public class BinaryHeapOpenSet implements IOpenSet {
* @param index2 The second index
*/
protected void swap(int index1, int index2) {
//sanity checks, disabled because of performance hit
//if (array[index1].heapPosition != index1) throw new IllegalStateException();
//if (array[index2].heapPosition != index2) throw new IllegalStateException();
PathNode tmp = array[index1];
array[index1] = array[index2];
array[index2] = tmp;
tmp.heapPosition = index2;
array[index1].heapPosition = index1;
}
}

10
src/main/java/baritone/bot/pathing/calc/openset/FibonacciHeapOpenSet.java
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@ -1,7 +1,7 @@
package baritone.bot.pathing.calc.openset;
import baritone.bot.pathing.util.FibonacciHeap;
import baritone.bot.pathing.calc.PathNode;
import baritone.bot.pathing.util.FibonacciHeap;
/**
* Wrapper adapter between FibonacciHeap and OpenSet
@ -17,6 +17,12 @@ public class FibonacciHeapOpenSet extends FibonacciHeap implements IOpenSet {
@Override
public PathNode removeLowest() {
return (PathNode) super.removeMin();
PathNode pn = super.removeMin();
pn.parent = null;
return pn;
}
public void update(PathNode node) {
super.decreaseKey(node.parent, node.combinedCost);
}
}

7
src/main/java/baritone/bot/pathing/calc/openset/IOpenSet.java
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@ -27,4 +27,11 @@ public interface IOpenSet {
* @return The minimum element in the heap
*/
PathNode removeLowest();
/**
* A faster path has been found to this node, decreasing its cost. Perform a decrease-key operation.
*
* @param node The node
*/
void update(PathNode node);
}

8
src/main/java/baritone/bot/pathing/calc/openset/LinkedListOpenSet.java
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@ -9,10 +9,12 @@ import baritone.bot.pathing.calc.PathNode;
public class LinkedListOpenSet implements IOpenSet {
private Node first = null;
@Override
public boolean isEmpty() {
return first == null;
}
@Override
public void insert(PathNode pathNode) {
Node node = new Node();
node.val = pathNode;
@ -20,6 +22,12 @@ public class LinkedListOpenSet implements IOpenSet {
first = node;
}
@Override
public void update(PathNode node) {
}
@Override
public PathNode removeLowest() {
if (first == null) {
return null;

11
src/main/java/baritone/bot/pathing/util/FibonacciHeap.java
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@ -24,6 +24,8 @@ package baritone.bot.pathing.util;
*/
//package com.bluemarsh.graphmaker.core.util;
import baritone.bot.pathing.calc.PathNode;
/**
* This class implements a Fibonacci heap data structure. Much of the
* code in this class is based on the algorithms in Chapter 21 of the
@ -233,8 +235,9 @@ public class FibonacciHeap {
* @param key key value associated with data object.
* @return newly created heap node.
*/
public Node insert(Object x, double key) {
public Node insert(PathNode x, double key) {
Node node = new Node(x, key);
x.parent = node;
// concatenate node into min list
if (min != null) {
node.right = min;
@ -271,7 +274,7 @@ public class FibonacciHeap {
*
* @return data object with the smallest key.
*/
public Object removeMin() {
public PathNode removeMin() {
Node z = min;
if (z == null) {
return null;
@ -329,7 +332,7 @@ public class FibonacciHeap {
/**
* Data object for this node, holds the key value.
*/
private Object data;
private PathNode data;
/**
* Key value for this node.
*/
@ -368,7 +371,7 @@ public class FibonacciHeap {
* @param data data object to associate with this node
* @param key key value for this data object
*/
public Node(Object data, double key) {
public Node(PathNode data, double key) {
this.data = data;
this.key = key;
right = this;

82
src/test/java/baritone/bot/pathing/calc/openset/OpenSetsTest.java
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@ -5,6 +5,8 @@ import baritone.bot.pathing.goals.GoalBlock;
import net.minecraft.util.math.BlockPos;
import org.junit.Test;
import java.util.*;
import static org.junit.Assert.*;
public class OpenSetsTest {
@ -19,6 +21,29 @@ public class OpenSetsTest {
}
}
public void removeAndTest(int amount, IOpenSet[] test, Optional<Collection<PathNode>> mustContain) {
double[][] results = new double[test.length][amount];
for (int i = 0; i < test.length; i++) {
long before = System.currentTimeMillis();
for (int j = 0; j < amount; j++) {
PathNode pn = test[i].removeLowest();
if (mustContain.isPresent() && !mustContain.get().contains(pn)) {
throw new IllegalStateException(mustContain.get() + " " + pn);
}
results[i][j] = pn.combinedCost;
}
System.out.println(test[i].getClass() + " " + (System.currentTimeMillis() - before));
}
for (int j = 0; j < amount; j++) {
for (int i = 1; i < test.length; i++) {
assertEquals(results[i][j], results[0][j], 0);
}
}
for (int i = 0; i < amount - 1; i++) {
assertTrue(results[0][i] < results[0][i + 1]);
}
}
public void testSize(int size) {
System.out.println("Testing size " + size);
// Include LinkedListOpenSet even though it's not performant because I absolutely trust that it behaves properly
@ -27,13 +52,25 @@ public class OpenSetsTest {
for (IOpenSet set : test) {
assertTrue(set.isEmpty());
}
// generate the pathnodes that we'll be testing the sets on
PathNode[] toInsert = new PathNode[size];
for (int i = 0; i < size; i++) {
PathNode pn = new PathNode(new BlockPos(0, 0, 0), new GoalBlock(new BlockPos(0, 0, 0)));
pn.combinedCost = Math.random();
toInsert[i] = pn;
}
// create a list of what the first removals should be
ArrayList<PathNode> copy = new ArrayList<>(Arrays.asList(toInsert));
copy.sort(Comparator.comparingDouble(pn -> pn.combinedCost));
Set<PathNode> lowestQuarter = new HashSet<>(copy.subList(0, size / 4));
// all opensets should be empty; nothing has been inserted yet
for (IOpenSet set : test) {
assertTrue(set.isEmpty());
}
System.out.println("Insertion");
for (IOpenSet set : test) {
long before = System.currentTimeMillis();
@ -43,23 +80,46 @@ public class OpenSetsTest {
//all three take either 0 or 1ms to insert up to 10,000 nodes
//linkedlist takes 0ms most often (because there's no array resizing or allocation there, just pointer shuffling)
}
// all opensets should now be full
for (IOpenSet set : test) {
assertFalse(set.isEmpty());
}
System.out.println("Removal");
double[][] results = new double[test.length][size];
for (int i = 0; i < test.length; i++) {
long before = System.currentTimeMillis();
for (int j = 0; j < size; j++) {
results[i][j] = test[i].removeLowest().combinedCost;
System.out.println("Removal round 1");
// remove a quarter of the nodes and verify that they are indeed the size/4 lowest ones
removeAndTest(size / 4, test, Optional.of(lowestQuarter));
// none of them should be empty (sanity check)
for (IOpenSet set : test) {
assertFalse(set.isEmpty());
}
System.out.println(test[i].getClass() + " " + (System.currentTimeMillis() - before));
int cnt = 0;
for (int i = 0; cnt < size / 2 && i < size; i++) {
if (lowestQuarter.contains(toInsert[i])) { // these were already removed and can't be updated to test
continue;
}
for (int j = 0; j < size; j++) {
for (int i = 1; i < test.length; i++) {
assertEquals(results[i][j], results[0][j], 0);
toInsert[i].combinedCost *= Math.random();
// multiplying it by a random number between 0 and 1 is guaranteed to decrease it
for (IOpenSet set : test) {
// it's difficult to benchmark these individually because if you modify all at once then update then
// it breaks the internal consistency of the heaps.
// you have to call update every time you modify a node.
set.update(toInsert[i]);
}
cnt++;
}
//still shouldn't be empty
for (IOpenSet set : test) {
assertFalse(set.isEmpty());
}
System.out.println("Removal round 2");
// remove the remaining 3/4
removeAndTest(size - size / 4, test, Optional.empty());
// every set should now be empty
for (IOpenSet set : test) {
assertTrue(set.isEmpty());
}