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/*
* This file is part of choco-solver, http://choco-solver.org/
*
* Copyright (c) 2024, IMT Atlantique. All rights reserved.
*
* Licensed under the BSD 4-clause license.
*
* See LICENSE file in the project root for full license information.
*/
package org.chocosolver.memory.structure;
import org.chocosolver.memory.IEnvironment;
import org.chocosolver.memory.IStateBitSet;
import org.chocosolver.memory.IStateInt;
import org.chocosolver.memory.IStateLong;
import java.lang.reflect.Array;
public class S64BitSet implements IStateBitSet {
private final static boolean CHECK = false;
/*
* BitSets are packed into arrays of "words." Currently a word is
* a long, which consists of 64 bits, requiring 6 address bits.
* The choice of word size is determined purely by performance concerns.
*/
private final static int ADDRESS_BITS_PER_WORD = 6;
protected final static int BITS_PER_WORD = 1 << ADDRESS_BITS_PER_WORD;
/* Used to shift left or right for a partial word mask */
protected static final long WORD_MASK = 0xffffffffffffffffL;
/**
* The current environment.
*/
private final IEnvironment environment;
/**
* The internal field corresponding to the serialField "bits".
*/
protected IStateLong[] words;
/**
* The number of words in the logical size of this BitSet.
*/
protected final IStateInt wordsInUse;
/**
* Given a bit index, return word index containing it.
*
* @param bitIndex bit index
*/
protected static int wordIndex(int bitIndex) {
return bitIndex >> ADDRESS_BITS_PER_WORD;
}
/**
* Check that the given index is strictly positive.
*
* @param index the index
* @throws IndexOutOfBoundsException if the index is negative
*/
private static void requirePositiveIndex(final int index) {
if (index < 0) {
throw new IndexOutOfBoundsException(
"Positive index expected. Got " + index);
}
}
/**
* Every public method must preserve these invariants.
*/
private void checkInvariants() {
assert (wordsInUse.get() == 0 || words[wordsInUse.get() - 1].get() != 0);
assert (wordsInUse.get() >= 0 && wordsInUse.get() <= words.length);
assert (wordsInUse.get() == words.length || words[wordsInUse.get()].get() == 0);
}
/**
* Set the field wordsInUse with the logical size in words of the bit
* set. WARNING:This method assumes that the number of words actually
* in use is less than or equal to the current value of wordsInUse!
*/
private void recalculateWordsInUse() {
// Traverse the bitset until a used word is found
int i;
int n = wordsInUse.get();
for (i = n - 1; i >= 0; i--)
if (words[i].get() != 0)
break;
if (i + 1 < n) {
wordsInUse.set(i + 1); // The new logical size
}
}
/**
* Creates a new bit set. All bits are initially false.
*
* @param environment bactrackable environment
*/
public S64BitSet(IEnvironment environment) {
this.environment = environment;
this.wordsInUse = environment.makeInt(0);
initWords(BITS_PER_WORD);
}
/**
* Creates a bit set whose initial size is large enough to explicitly
* represent bits with indices in the range 0 through
* nbits-1. All bits are initially false.
*
* @param environment backtrackable environment
* @param nbits the initial size of the bit set.
* @throws NegativeArraySizeException if the specified initial size
* is negative.
*/
public S64BitSet(IEnvironment environment, int nbits) {
this.environment = environment;
this.wordsInUse = environment.makeInt(0);
// nbits can't be negative; size 0 is OK
if (nbits < 0)
throw new NegativeArraySizeException("nbits < 0: " + nbits);
initWords(nbits);
}
private void initWords(int nbits) {
words = new IStateLong[wordIndex(nbits - 1) + 1];
for (int i = 0; i < words.length; i++) words[i] = this.environment.makeLong(0);
if (CHECK) checkInvariants();
}
/**
* Ensures that the BitSet can hold enough words.
*
* @param wordsRequired the minimum acceptable number of words.
*/
public void ensureCapacity(int wordsRequired) {
if (words.length < wordsRequired) {
// Allocate larger of doubled size or required size
int request = Math.max(2 * words.length, wordsRequired);
int oldSize = words.length;
words = copyOf(words, request);
for (int i = oldSize; i < request; i++) {
words[i] = environment.makeLong(0);
}
}
}
@SuppressWarnings({"unchecked"})
public static T[] copyOf(T[] original, int newLength) {
return (T[]) copyOf(original, newLength, original.getClass());
}
@SuppressWarnings({"unchecked", "SuspiciousSystemArraycopy", "RedundantCast"})
public static T[] copyOf(U[] original, int newLength, Class newType) {
T[] copy = ((Object) newType == (Object) Object[].class)
? (T[]) new Object[newLength]
: (T[]) Array.newInstance(newType.getComponentType(), newLength);
System.arraycopy(original, 0, copy, 0,
Math.min(original.length, newLength));
return copy;
}
/**
* Ensures that the BitSet can accommodate a given wordIndex,
* temporarily violating the invariants. The caller must
* restore the invariants before returning to the user,
* possibly using recalculateWordsInUse().
*
* @param wordIndex the index to be accommodated.
*/
private void expandTo(int wordIndex) {
int wordsRequired = wordIndex + 1;
if (wordsInUse.get() < wordsRequired) {
ensureCapacity(wordsRequired);
wordsInUse.set(wordsRequired);
}
}
/**
* Checks that fromIndex ... toIndex is a valid range of bit indices.
*
* @param fromIndex starting index
* @param toIndex ending index
*/
private static void checkRange(int fromIndex, int toIndex) {
if (fromIndex < 0)
throw new IndexOutOfBoundsException("fromIndex < 0: " + fromIndex);
if (toIndex < 0)
throw new IndexOutOfBoundsException("toIndex < 0: " + toIndex);
if (fromIndex > toIndex)
throw new IndexOutOfBoundsException("fromIndex: " + fromIndex + " > toIndex: " + toIndex);
}
/**
* Sets the bit at the specified index to true.
*
* @param bitIndex a bit index.
* @throws IndexOutOfBoundsException if the specified index is negative.
* @since JDK1.0
*/
public void set(int bitIndex) {
requirePositiveIndex(bitIndex);
if (CHECK) checkInvariants();
int wordIndex = wordIndex(bitIndex);
expandTo(wordIndex);
words[wordIndex].set(words[wordIndex].get() | (1L << bitIndex)); // Restores invariants
if (CHECK) checkInvariants();
}
/**
* Sets the bit at the specified index to the specified value.
*
* @param bitIndex a bit index.
* @param value a boolean value to set.
* @throws IndexOutOfBoundsException if the specified index is negative.
* @since 1.4
*/
public void set(int bitIndex, boolean value) {
if (value)
set(bitIndex);
else
clear(bitIndex);
}
/**
* Sets the bits from the specified fromIndex (inclusive) to the
* specified toIndex (exclusive) to true.
*
* @param fromIndex index of the first bit to be set.
* @param toIndex index after the last bit to be set.
* @throws IndexOutOfBoundsException if fromIndex is negative,
* or toIndex is negative, or fromIndex is
* larger than toIndex.
* @since 1.4
*/
public void set(int fromIndex, int toIndex) {
checkRange(fromIndex, toIndex);
if (fromIndex == toIndex)
return;
// Increase capacity if necessary
int startWordIndex = wordIndex(fromIndex);
int endWordIndex = wordIndex(toIndex - 1);
expandTo(endWordIndex);
long firstWordMask = WORD_MASK << fromIndex;
long lastWordMask = WORD_MASK >>> -toIndex;
if (startWordIndex == endWordIndex) {
// Case 1: One word
words[startWordIndex].set(words[startWordIndex].get() | (firstWordMask & lastWordMask));
} else {
// Case 2: Multiple words
// Handle first word
words[startWordIndex].set(words[startWordIndex].get() | firstWordMask);
// Handle intermediate words, if any
for (int i = startWordIndex + 1; i < endWordIndex; i++)
words[i].set(WORD_MASK);
// Handle last word (restores invariants)
words[endWordIndex].set(words[endWordIndex].get() | lastWordMask);
}
if (CHECK) checkInvariants();
}
/**
* Sets the bit specified by the index to false.
*
* @param bitIndex the index of the bit to be cleared.
* @throws IndexOutOfBoundsException if the specified index is negative.
* @since JDK1.0
*/
public void clear(int bitIndex) {
requirePositiveIndex(bitIndex);
int wordIndex = wordIndex(bitIndex);
int n = wordsInUse.get();
if (wordIndex >= n)
return;
words[wordIndex].set(words[wordIndex].get() & ~(1L << bitIndex));
//if(wordIndex == n-1)
recalculateWordsInUse();
if (CHECK) checkInvariants();
}
/**
* Sets the bits from the specified fromIndex (inclusive) to the
* specified toIndex (exclusive) to false.
*
* @param fromIndex index of the first bit to be cleared.
* @param toIndex index after the last bit to be cleared.
* @throws IndexOutOfBoundsException if fromIndex is negative,
* or toIndex is negative, or fromIndex is
* larger than toIndex.
* @since 1.4
*/
public void clear(int fromIndex, int toIndex) {
checkRange(fromIndex, toIndex);
if (fromIndex == toIndex)
return;
int wiu = wordsInUse.get();
int startWordIndex = wordIndex(fromIndex);
if (startWordIndex >= wiu)
return;
int endWordIndex = wordIndex(toIndex - 1);
if (endWordIndex >= wiu) {
toIndex = length();
endWordIndex = wiu - 1;
}
long firstWordMask = WORD_MASK << fromIndex;
long lastWordMask = WORD_MASK >>> -toIndex;
if (startWordIndex == endWordIndex) {
// Case 1: One word
words[startWordIndex].set(words[startWordIndex].get() & ~(firstWordMask & lastWordMask));
} else {
// Case 2: Multiple words
// Handle first word
words[startWordIndex].set(words[startWordIndex].get() & ~firstWordMask);
// Handle intermediate words, if any
for (int i = startWordIndex + 1; i < endWordIndex; i++)
words[i].set(0);
// Handle last word
words[endWordIndex].set(words[endWordIndex].get() & ~lastWordMask);
}
//if(endWordIndex < wiu)
recalculateWordsInUse();
if (CHECK) checkInvariants();
}
/**
* Sets all of the bits in this BitSet to false.
*
* @since 1.4
*/
public void clear() {
/*while (wordsInUse.get() > 0)
wordsInUse.set(wordsInUse.get() - 1);
words[wordsInUse.get()].set(0); */
for (IStateLong word : words) {
word.set(0);
}
wordsInUse.set(0);
if (CHECK) checkInvariants();
}
/**
* Returns the value of the bit with the specified index. The value
* is true if the bit with the index bitIndex
* is currently set in this BitSet; otherwise, the result
* is false.
*
* @param bitIndex the bit index.
* @return the value of the bit with the specified index.
* @throws IndexOutOfBoundsException if the specified index is negative.
*/
final public boolean get(final int bitIndex) {
requirePositiveIndex(bitIndex);
if (CHECK) checkInvariants();
int wordIndex = bitIndex >> ADDRESS_BITS_PER_WORD; //wordIndex(bitIndex);
return (wordIndex < wordsInUse.get())
&& ((words[wordIndex].get() & (1L << bitIndex)) != 0);
}
/**
* Returns the index of the first bit that is set to {@code true}
* that occurs on or after the specified starting index. If no such
* bit exists then {@code -1} is returned.
*
* To iterate over the {@code true} bits in a {@code BitSet},
* use the following loop:
*
* {@code
* for (int i = bs.nextSetBit(0); i >= 0; i = bs.nextSetBit(i+1)) {
* // operate on index i here
* }}
*
* @param fromIndex the index to start checking from (inclusive)
* @return the index of the next set bit, or {@code -1} if there
* is no such bit
* @throws IndexOutOfBoundsException if the specified index is negative
* @since 1.4
*/
public int nextSetBit(int fromIndex) {
if (fromIndex < 0) {
fromIndex = 0;
}
int wiu = wordsInUse.get();
int u = wordIndex(fromIndex);
if (u >= wiu)
return -1;
long word = words[u].get() & (WORD_MASK << fromIndex);
while (true) {
if (word != 0)
return (u * BITS_PER_WORD) + Long.numberOfTrailingZeros(word);
if (++u == wiu)
return -1;
word = words[u].get();
}
}
/**
* Returns the index of the first bit that is set to {@code false}
* that occurs on or after the specified starting index.
*
* @param fromIndex the index to start checking from (inclusive)
* @return the index of the next clear bit
* @throws IndexOutOfBoundsException if the specified index is negative
* @since 1.4
*/
public int nextClearBit(int fromIndex) {
// Neither spec nor implementation handle bitsets of maximal length.
// See 4816253.
if (fromIndex < 0) {
fromIndex = 0;
}
int wiu = wordsInUse.get();
int u = wordIndex(fromIndex);
if (u >= wiu)
return fromIndex;
long word = ~words[u].get() & (WORD_MASK << fromIndex);
while (true) {
if (word != 0)
return (u * BITS_PER_WORD) + Long.numberOfTrailingZeros(word);
if (++u == wiu)
return wiu * BITS_PER_WORD;
word = ~words[u].get();
}
}
/**
* Returns the index of the nearest bit that is set to {@code true}
* that occurs on or before the specified starting index.
* If no such bit exists, or if {@code -1} is given as the
* starting index, then {@code -1} is returned.
*
* To iterate over the {@code true} bits in a {@code BitSet},
* use the following loop:
*
* {@code
* for (int i = bs.length(); (i = bs.previousSetBit(i-1)) >= 0; ) {
* // operate on index i here
* }}
*
* @param fromIndex the index to start checking from (inclusive)
* @return the index of the previous set bit, or {@code -1} if there
* is no such bit
* @throws IndexOutOfBoundsException if the specified index is less
* than {@code -1}
* @since 1.7
*/
public int prevSetBit(int fromIndex) {
if (fromIndex < 0) {
return -1;
}
int u = wordIndex(fromIndex);
if (u >= wordsInUse.get())
return length() - 1;
long word = words[u].get() & (WORD_MASK >>> -(fromIndex + 1));
while (true) {
if (word != 0)
return (u + 1) * BITS_PER_WORD - 1 - Long.numberOfLeadingZeros(word);
if (u-- == 0)
return -1;
word = words[u].get();
}
}
/**
* Returns the index of the nearest bit that is set to {@code false}
* that occurs on or before the specified starting index.
* If no such bit exists, or if {@code -1} is given as the
* starting index, then {@code -1} is returned.
*
* @param fromIndex the index to start checking from (inclusive)
* @return the index of the previous clear bit, or {@code -1} if there
* is no such bit
* @throws IndexOutOfBoundsException if the specified index is less
* than {@code -1}
* @since 1.7
*/
public int prevClearBit(int fromIndex) {
if (fromIndex < 0) {
return -1;
}
int u = wordIndex(fromIndex);
if (u >= wordsInUse.get())
return fromIndex;
long word = ~words[u].get() & (WORD_MASK >>> -(fromIndex + 1));
while (true) {
if (word != 0)
return (u + 1) * BITS_PER_WORD - 1 - Long.numberOfLeadingZeros(word);
if (u-- == 0)
return -1;
word = ~words[u].get();
}
}
/**
* Returns the "logical size" of this BitSet: the index of
* the highest set bit in the BitSet plus one. Returns zero
* if the BitSet contains no set bits.
*
* @return the logical size of this BitSet.
* @since 1.2
*/
public int length() {
int wiu = wordsInUse.get();
if (wiu == 0)
return 0;
return BITS_PER_WORD * (wiu - 1) +
(BITS_PER_WORD - Long.numberOfLeadingZeros(words[wiu - 1].get()));
}
/**
* Returns true if this BitSet contains no bits that are set
* to true.
*
* @return boolean indicating whether this BitSet is empty.
* @since 1.4
*/
public boolean isEmpty() {
return wordsInUse.get() == 0;
}
/**
* Returns the number of bits set to true in this
* BitSet.
*
* @return the number of bits set to true in this
* BitSet.
* @since 1.4
*/
public int cardinality() {
int sum = 0;
for (int i = wordsInUse.get() - 1; i >= 0; i--)
sum += Long.bitCount(words[i].get());
return sum;
}
public int hashCode() {
long h = 1234;
for (int i = wordsInUse.get(); --i >= 0; )
h ^= words[i].get() * (i + 1);
return (int) ((h >> 32) ^ h);
}
/**
* Returns the number of bits of space actually in use by this
* BitSet to represent bit values.
* The maximum element in the set is the size - 1st element.
*
* @return the number of bits currently in this bit set.
*/
public int size() {
return words.length * BITS_PER_WORD;
}
@Override
public boolean equals(final Object o) {
if (this == o) {
return true;
}
if (!(o instanceof IStateBitSet)) {
return false;
}
final IStateBitSet that = (IStateBitSet) o;
// Fail fast.
if (this.cardinality() != that.cardinality()) {
return false;
}
// Same cardinality. Iterate over the bit sets. Those must be sets in 'that'
// as well.
for (int i = nextSetBit(0); i >= 0; i = nextSetBit(i + 1)) {
if (!that.get(i)) {
return false;
}
}
return true;
}
public String toString() {
if (CHECK) checkInvariants();
int numBits = (wordsInUse.get() > 128) ?
cardinality() : wordsInUse.get() * BITS_PER_WORD;
StringBuilder b = new StringBuilder(6 * numBits + 2);
b.append('{');
int i = nextSetBit(0);
if (i != -1) {
b.append(i);
for (i = nextSetBit(i + 1); i >= 0; i = nextSetBit(i + 1)) {
int endOfRun = nextClearBit(i);
do {
b.append(", ").append(i);
}
while (++i < endOfRun);
}
}
b.append('}');
return b.toString();
}
}