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SquidLib platform-independent logic and utility code. Please refer to
https://github.com/SquidPony/SquidLib .
/*******************************************************************************
* Copyright 2011 See AUTHORS file.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
******************************************************************************/
package squidpony.squidmath;
import java.io.Serializable;
import java.util.NoSuchElementException;
/** An unordered set that uses short keys. This implementation uses cuckoo hashing using 3 hashes, random walking, and a
* small stash for problematic keys. No allocation is done except when growing the table size. Used internally by
* CoordPacker, and unlikely to be used outside of it.
*
* This set performs very fast contains and remove (typically O(1), worst case O(log(n))). Add may be a bit slower,
* depending on hash collisions. Load factors greater than 0.91 greatly increase the chances the set will have to rehash
* to the next higher POT size.
* @author Nathan Sweet
* Ported from libGDX by Tommy Ettinger on 10/19/2015.
*/
public class ShortSet implements Serializable{
private static final long serialVersionUID = -4390851800502156007L;
private static final int PRIME2 = 0xb4b82e39;
private static final int PRIME3 = 0xced1c241;
private static final short EMPTY = 0;
public int size;
short[] keyTable;
int capacity, stashSize;
boolean hasZeroValue;
private float loadFactor;
private int hashShift, threshold;
private int stashCapacity;
private int pushIterations;
private int mask;
private static long rngState;
private ShortSetIterator iterator1, iterator2;
/** Creates a new sets with an initial capacity of 32 and a load factor of 0.8. This set will hold 25 items before growing the
* backing table. */
public ShortSet() {
this(32, 0.8f);
}
/** Creates a new set with a load factor of 0.8. This set will hold initialCapacity * 0.8 items before growing the backing
* table. */
public ShortSet(int initialCapacity) {
this(initialCapacity, 0.8f);
}
/** Creates a new set with the specified initial capacity and load factor. This set will hold initialCapacity * loadFactor items
* before growing the backing table. */
public ShortSet(int initialCapacity, float loadFactor) {
if (initialCapacity < 0) throw new IllegalArgumentException("initialCapacity must be >= 0: " + initialCapacity);
if (initialCapacity > 1 << 30) throw new IllegalArgumentException("initialCapacity is too large: " + initialCapacity);
capacity = nextPowerOfTwo(initialCapacity);
rngState = (long) ((Math.random() - 0.5) * 0x10000000000000L)
^ (long) (((Math.random() - 0.5) * 2.0) * 0x8000000000000000L);
if (loadFactor <= 0) throw new IllegalArgumentException("loadFactor must be > 0: " + loadFactor);
this.loadFactor = loadFactor;
threshold = (int)(capacity * loadFactor);
mask = capacity - 1;
hashShift = 31 - Integer.numberOfTrailingZeros(capacity);
stashCapacity = Math.max(3, (int)Math.ceil(Math.log(capacity)) * 2);
pushIterations = Math.max(Math.min(capacity, 8), (int)Math.sqrt(capacity) / 8);
keyTable = new short[capacity + stashCapacity];
}
/** Creates a new map identical to the specified map. */
public ShortSet(ShortSet map) {
this(map.capacity, map.loadFactor);
stashSize = map.stashSize;
System.arraycopy(map.keyTable, 0, keyTable, 0, map.keyTable.length);
size = map.size;
hasZeroValue = map.hasZeroValue;
}
/** Returns true if the key was not already in the set. */
public boolean add (short key) {
if (key == 0) {
if (hasZeroValue) return false;
hasZeroValue = true;
size++;
return true;
}
short[] keyTable = this.keyTable;
// Check for existing keys.
int index1 = key & mask;
short key1 = keyTable[index1];
if (key1 == key) return false;
int index2 = hash2(key);
short key2 = keyTable[index2];
if (key2 == key) return false;
int index3 = hash3(key);
short key3 = keyTable[index3];
if (key3 == key) return false;
// Find key in the stash.
for (int i = capacity, n = i + stashSize; i < n; i++)
if (keyTable[i] == key) return false;
// Check for empty buckets.
if (key1 == EMPTY) {
keyTable[index1] = key;
if (size++ >= threshold) resize(capacity << 1);
return true;
}
if (key2 == EMPTY) {
keyTable[index2] = key;
if (size++ >= threshold) resize(capacity << 1);
return true;
}
if (key3 == EMPTY) {
keyTable[index3] = key;
if (size++ >= threshold) resize(capacity << 1);
return true;
}
push(key, index1, key1, index2, key2, index3, key3);
return true;
}
public void addAll (ShortVLA array) {
addAll(array, 0, array.size);
}
public void addAll (ShortVLA array, int offset, int length) {
if (offset + length > array.size)
throw new IllegalArgumentException("offset + length must be <= size: " + offset + " + " + length + " <= " + array.size);
addAll(array.items, offset, length);
}
public void addAll (short... array) {
addAll(array, 0, array.length);
}
public void addAll (short[] array, int offset, int length) {
ensureCapacity(length);
for (int i = offset, n = i + length; i < n; i++)
add(array[i]);
}
public void addAll (ShortSet set) {
ensureCapacity(set.size);
ShortSetIterator iterator = set.iterator();
while (iterator.hasNext)
add(iterator.next());
}
/** Skips checks for existing keys. */
private void addResize (short key) {
if (key == 0) {
hasZeroValue = true;
return;
}
// Check for empty buckets.
int index1 = key & mask;
short key1 = keyTable[index1];
if (key1 == EMPTY) {
keyTable[index1] = key;
if (size++ >= threshold) resize(capacity << 1);
return;
}
int index2 = hash2(key);
short key2 = keyTable[index2];
if (key2 == EMPTY) {
keyTable[index2] = key;
if (size++ >= threshold) resize(capacity << 1);
return;
}
int index3 = hash3(key);
short key3 = keyTable[index3];
if (key3 == EMPTY) {
keyTable[index3] = key;
if (size++ >= threshold) resize(capacity << 1);
return;
}
push(key, index1, key1, index2, key2, index3, key3);
}
private void push (short insertKey, int index1, short key1, int index2, short key2, int index3, short key3) {
short[] keyTable = this.keyTable;
int mask = this.mask;
// Push keys until an empty bucket is found.
short evictedKey;
int i = 0, pushIterations = this.pushIterations;
do {
// Replace the key and value for one of the hashes.
switch (DiverRNG.determineBounded(++rngState, 3)) {
case 0:
evictedKey = key1;
keyTable[index1] = insertKey;
break;
case 1:
evictedKey = key2;
keyTable[index2] = insertKey;
break;
default:
evictedKey = key3;
keyTable[index3] = insertKey;
break;
}
// If the evicted key hashes to an empty bucket, put it there and stop.
index1 = evictedKey & mask;
key1 = keyTable[index1];
if (key1 == EMPTY) {
keyTable[index1] = evictedKey;
if (size++ >= threshold) resize(capacity << 1);
return;
}
index2 = hash2(evictedKey);
key2 = keyTable[index2];
if (key2 == EMPTY) {
keyTable[index2] = evictedKey;
if (size++ >= threshold) resize(capacity << 1);
return;
}
index3 = hash3(evictedKey);
key3 = keyTable[index3];
if (key3 == EMPTY) {
keyTable[index3] = evictedKey;
if (size++ >= threshold) resize(capacity << 1);
return;
}
if (++i == pushIterations) break;
insertKey = evictedKey;
} while (true);
addStash(evictedKey);
}
private void addStash (short key) {
if (stashSize == stashCapacity) {
// Too many pushes occurred and the stash is full, increase the table size.
resize(capacity << 1);
add(key);
return;
}
// Store key in the stash.
int index = capacity + stashSize;
keyTable[index] = key;
stashSize++;
size++;
}
/** Returns true if the key was removed. */
public boolean remove (short key) {
if (key == 0) {
if (!hasZeroValue) return false;
hasZeroValue = false;
size--;
return true;
}
int index = key & mask;
if (keyTable[index] == key) {
keyTable[index] = EMPTY;
size--;
return true;
}
index = hash2(key);
if (keyTable[index] == key) {
keyTable[index] = EMPTY;
size--;
return true;
}
index = hash3(key);
if (keyTable[index] == key) {
keyTable[index] = EMPTY;
size--;
return true;
}
return removeStash(key);
}
boolean removeStash (short key) {
short[] keyTable = this.keyTable;
for (int i = capacity, n = i + stashSize; i < n; i++) {
if (keyTable[i] == key) {
removeStashIndex(i);
size--;
return true;
}
}
return false;
}
void removeStashIndex (int index) {
// If the removed location was not last, move the last tuple to the removed location.
stashSize--;
int lastIndex = capacity + stashSize;
if (index < lastIndex) keyTable[index] = keyTable[lastIndex];
}
/** Reduces the size of the backing arrays to be the specified capacity or less. If the capacity is already less, nothing is
* done. If the set contains more items than the specified capacity, the next highest power of two capacity is used instead. */
public void shrink (int maximumCapacity) {
if (maximumCapacity < 0) throw new IllegalArgumentException("maximumCapacity must be >= 0: " + maximumCapacity);
if (size > maximumCapacity) maximumCapacity = size;
if (capacity <= maximumCapacity) return;
maximumCapacity = nextPowerOfTwo(maximumCapacity);
resize(maximumCapacity);
}
/** Clears the map and reduces the size of the backing arrays to be the specified capacity if they are larger. */
public void clear (int maximumCapacity) {
if (capacity <= maximumCapacity) {
clear();
return;
}
hasZeroValue = false;
size = 0;
resize(maximumCapacity);
}
public void clear () {
if (size == 0) return;
short[] keyTable = this.keyTable;
for (int i = capacity + stashSize; i-- > 0;)
keyTable[i] = EMPTY;
size = 0;
stashSize = 0;
hasZeroValue = false;
}
public boolean contains (short key) {
if (key == 0) return hasZeroValue;
int index = key & mask;
if (keyTable[index] != key) {
index = hash2(key);
if (keyTable[index] != key) {
index = hash3(key);
if (keyTable[index] != key) return containsKeyStash(key);
}
}
return true;
}
private boolean containsKeyStash (short key) {
short[] keyTable = this.keyTable;
for (int i = capacity, n = i + stashSize; i < n; i++)
if (keyTable[i] == key) return true;
return false;
}
public int first () {
if (hasZeroValue) return 0;
short[] keyTable = this.keyTable;
for (int i = 0, n = capacity + stashSize; i < n; i++)
if (keyTable[i] != EMPTY) return keyTable[i];
throw new IllegalStateException("ShortSet is empty.");
}
/** Increases the size of the backing array to accommodate the specified number of additional items. Useful before adding many
* items to avoid multiple backing array resizes. */
public void ensureCapacity (int additionalCapacity) {
int sizeNeeded = size + additionalCapacity;
if (sizeNeeded >= threshold) resize(nextPowerOfTwo((int)(sizeNeeded / loadFactor)));
}
private void resize (int newSize) {
int oldEndIndex = capacity + stashSize;
capacity = newSize;
threshold = (int)(newSize * loadFactor);
mask = newSize - 1;
hashShift = 31 - Integer.numberOfTrailingZeros(newSize);
stashCapacity = Math.max(3, (int)Math.ceil(Math.log(newSize)) * 2);
pushIterations = Math.max(Math.min(newSize, 8), (int)Math.sqrt(newSize) / 8);
short[] oldKeyTable = keyTable;
keyTable = new short[newSize + stashCapacity];
int oldSize = size;
size = hasZeroValue ? 1 : 0;
stashSize = 0;
if (oldSize > 0) {
for (int i = 0; i < oldEndIndex; i++) {
short key = oldKeyTable[i];
if (key != EMPTY) addResize(key);
}
}
}
private int hash2 (int h) {
h *= PRIME2;
return (h ^ h >>> hashShift) & mask;
}
private int hash3 (int h) {
h *= PRIME3;
return (h ^ h >>> hashShift) & mask;
}
@Override
public int hashCode () {
int h = 0;
for (int i = 0, n = capacity + stashSize; i < n; i++)
if (keyTable[i] != EMPTY) h += keyTable[i];
return h;
}
@Override
public boolean equals (Object obj) {
if (!(obj instanceof ShortSet)) return false;
ShortSet other = (ShortSet)obj;
if (other.size != size) return false;
if (other.hasZeroValue != hasZeroValue) return false;
for (int i = 0, n = capacity + stashSize; i < n; i++)
if (keyTable[i] != EMPTY && !other.contains(keyTable[i])) return false;
return true;
}
@Override
public String toString () {
if (size == 0) return "[]";
StringBuilder buffer = new StringBuilder(32);
buffer.append('[');
short[] keyTable = this.keyTable;
int i = keyTable.length;
if (hasZeroValue)
buffer.append("0");
else {
while (i-- > 0) {
int key = keyTable[i];
if (key == EMPTY) continue;
buffer.append(key);
break;
}
}
while (i-- > 0) {
int key = keyTable[i];
if (key == EMPTY) continue;
buffer.append(", ").append(key);
}
return buffer.append(']').toString();
}
/**
* Gets a random short from this ShortSet, using the given {@link IRNG} to generate random values.
* If this ShortSet is empty, throws an UnsupportedOperationException. This method operates in linear time, unlike
* the random item retrieval methods in {@link OrderedSet} and {@link OrderedMap}, which take constant time.
* @param rng an {@link IRNG}, such as {@link RNG} or {@link GWTRNG}
* @return a random short from this ShortSet
*/
public short random(IRNG rng)
{
if (size <= 0) {
throw new UnsupportedOperationException("ShortSet cannot be empty when getting a random element");
}
int n = rng.nextInt(size);
short s = 0;
ShortSet.ShortSetIterator ssi = iterator();
while (n-- >= 0 && ssi.hasNext)
s = ssi.next();
ssi.reset();
return s;
}
private static int nextPowerOfTwo(int n)
{
int highest = Integer.highestOneBit(n);
return (highest == NumberTools.lowestOneBit(n)) ? highest : highest << 1;
}
/** Returns an iterator for the keys in the set. Remove is supported. Note that the same iterator instance is returned each time
* this method is called. Use the {@link ShortSetIterator} constructor for nested or multithreaded iteration. */
public ShortSetIterator iterator () {
if (iterator1 == null) {
iterator1 = new ShortSetIterator(this);
iterator2 = new ShortSetIterator(this);
}
if (!iterator1.valid) {
iterator1.reset();
iterator1.valid = true;
iterator2.valid = false;
return iterator1;
}
iterator2.reset();
iterator2.valid = true;
iterator1.valid = false;
return iterator2;
}
public static ShortSet with (short... array) {
ShortSet set = new ShortSet();
set.addAll(array);
return set;
}
public static class ShortSetIterator {
static final int INDEX_ILLEGAL = -2;
static final int INDEX_ZERO = -1;
public boolean hasNext;
final ShortSet set;
int nextIndex, currentIndex;
boolean valid = true;
public ShortSetIterator(ShortSet set) {
this.set = set;
reset();
}
public void reset () {
currentIndex = INDEX_ILLEGAL;
nextIndex = INDEX_ZERO;
if (set.hasZeroValue)
hasNext = true;
else
findNextIndex();
}
void findNextIndex () {
hasNext = false;
short[] keyTable = set.keyTable;
for (int n = set.capacity + set.stashSize; ++nextIndex < n;) {
if (keyTable[nextIndex] != EMPTY) {
hasNext = true;
break;
}
}
}
public void remove () {
if (currentIndex == INDEX_ZERO && set.hasZeroValue) {
set.hasZeroValue = false;
} else if (currentIndex < 0) {
throw new IllegalStateException("next must be called before remove.");
} else if (currentIndex >= set.capacity) {
set.removeStashIndex(currentIndex);
nextIndex = currentIndex - 1;
findNextIndex();
} else {
set.keyTable[currentIndex] = EMPTY;
}
currentIndex = INDEX_ILLEGAL;
set.size--;
}
public short next () {
if (!hasNext) throw new NoSuchElementException();
if (!valid) throw new RuntimeException("ShortSetIterator cannot be used nested.");
short key = nextIndex == INDEX_ZERO ? 0 : set.keyTable[nextIndex];
currentIndex = nextIndex;
findNextIndex();
return key;
}
/** Returns a new array containing the remaining keys. */
public ShortVLA toArray () {
ShortVLA array = new ShortVLA(true, set.size);
while (hasNext)
array.add(next());
return array;
}
}
}