it.unimi.dsi.fastutil.shorts.ShortOpenHashSet Maven / Gradle / Ivy
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/*
* Copyright (C) 2002-2020 Sebastiano Vigna
*
* 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 it.unimi.dsi.fastutil.shorts;
import it.unimi.dsi.fastutil.Hash;
import it.unimi.dsi.fastutil.HashCommon;
import static it.unimi.dsi.fastutil.HashCommon.arraySize;
import static it.unimi.dsi.fastutil.HashCommon.maxFill;
import java.util.Arrays;
import java.util.Collection;
import java.util.Iterator;
import java.util.NoSuchElementException;
/**
* A type-specific hash set with with a fast, small-footprint implementation.
*
*
* Instances of this class use a hash table to represent a set. The table is
* filled up to a specified load factor, and then doubled in size to
* accommodate new entries. If the table is emptied below one fourth of
* the load factor, it is halved in size; however, the table is never reduced to
* a size smaller than that at creation time: this approach makes it possible to
* create sets with a large capacity in which insertions and deletions do not
* cause immediately rehashing. Moreover, halving is not performed when deleting
* entries from an iterator, as it would interfere with the iteration process.
*
*
* Note that {@link #clear()} does not modify the hash table size. Rather, a
* family of {@linkplain #trim() trimming methods} lets you control the size of
* the table; this is particularly useful if you reuse instances of this class.
*
* @see Hash
* @see HashCommon
*/
public class ShortOpenHashSet extends AbstractShortSet implements java.io.Serializable, Cloneable, Hash {
private static final long serialVersionUID = 0L;
private static final boolean ASSERTS = false;
/** The array of keys. */
protected transient short[] key;
/** The mask for wrapping a position counter. */
protected transient int mask;
/** Whether this set contains the null key. */
protected transient boolean containsNull;
/**
* The current table size. Note that an additional element is allocated for
* storing the null key.
*/
protected transient int n;
/**
* Threshold after which we rehash. It must be the table size times {@link #f}.
*/
protected transient int maxFill;
/**
* We never resize below this threshold, which is the construction-time {#n}.
*/
protected final transient int minN;
/** Number of entries in the set (including the null key, if present). */
protected int size;
/** The acceptable load factor. */
protected final float f;
/**
* Creates a new hash set.
*
*
* The actual table size will be the least power of two greater than
* {@code expected}/{@code f}.
*
* @param expected
* the expected number of elements in the hash set.
* @param f
* the load factor.
*/
public ShortOpenHashSet(final int expected, final float f) {
if (f <= 0 || f >= 1)
throw new IllegalArgumentException("Load factor must be greater than 0 and smaller than 1");
if (expected < 0)
throw new IllegalArgumentException("The expected number of elements must be nonnegative");
this.f = f;
minN = n = arraySize(expected, f);
mask = n - 1;
maxFill = maxFill(n, f);
key = new short[n + 1];
}
/**
* Creates a new hash set with {@link Hash#DEFAULT_LOAD_FACTOR} as load factor.
*
* @param expected
* the expected number of elements in the hash set.
*/
public ShortOpenHashSet(final int expected) {
this(expected, DEFAULT_LOAD_FACTOR);
}
/**
* Creates a new hash set with initial expected
* {@link Hash#DEFAULT_INITIAL_SIZE} elements and
* {@link Hash#DEFAULT_LOAD_FACTOR} as load factor.
*/
public ShortOpenHashSet() {
this(DEFAULT_INITIAL_SIZE, DEFAULT_LOAD_FACTOR);
}
/**
* Creates a new hash set copying a given collection.
*
* @param c
* a {@link Collection} to be copied into the new hash set.
* @param f
* the load factor.
*/
public ShortOpenHashSet(final Collection c, final float f) {
this(c.size(), f);
addAll(c);
}
/**
* Creates a new hash set with {@link Hash#DEFAULT_LOAD_FACTOR} as load factor
* copying a given collection.
*
* @param c
* a {@link Collection} to be copied into the new hash set.
*/
public ShortOpenHashSet(final Collection c) {
this(c, DEFAULT_LOAD_FACTOR);
}
/**
* Creates a new hash set copying a given type-specific collection.
*
* @param c
* a type-specific collection to be copied into the new hash set.
* @param f
* the load factor.
*/
public ShortOpenHashSet(final ShortCollection c, final float f) {
this(c.size(), f);
addAll(c);
}
/**
* Creates a new hash set with {@link Hash#DEFAULT_LOAD_FACTOR} as load factor
* copying a given type-specific collection.
*
* @param c
* a type-specific collection to be copied into the new hash set.
*/
public ShortOpenHashSet(final ShortCollection c) {
this(c, DEFAULT_LOAD_FACTOR);
}
/**
* Creates a new hash set using elements provided by a type-specific iterator.
*
* @param i
* a type-specific iterator whose elements will fill the set.
* @param f
* the load factor.
*/
public ShortOpenHashSet(final ShortIterator i, final float f) {
this(DEFAULT_INITIAL_SIZE, f);
while (i.hasNext())
add(i.nextShort());
}
/**
* Creates a new hash set with {@link Hash#DEFAULT_LOAD_FACTOR} as load factor
* using elements provided by a type-specific iterator.
*
* @param i
* a type-specific iterator whose elements will fill the set.
*/
public ShortOpenHashSet(final ShortIterator i) {
this(i, DEFAULT_LOAD_FACTOR);
}
/**
* Creates a new hash set using elements provided by an iterator.
*
* @param i
* an iterator whose elements will fill the set.
* @param f
* the load factor.
*/
public ShortOpenHashSet(final Iterator i, final float f) {
this(ShortIterators.asShortIterator(i), f);
}
/**
* Creates a new hash set with {@link Hash#DEFAULT_LOAD_FACTOR} as load factor
* using elements provided by an iterator.
*
* @param i
* an iterator whose elements will fill the set.
*/
public ShortOpenHashSet(final Iterator i) {
this(ShortIterators.asShortIterator(i));
}
/**
* Creates a new hash set and fills it with the elements of a given array.
*
* @param a
* an array whose elements will be used to fill the set.
* @param offset
* the first element to use.
* @param length
* the number of elements to use.
* @param f
* the load factor.
*/
public ShortOpenHashSet(final short[] a, final int offset, final int length, final float f) {
this(length < 0 ? 0 : length, f);
ShortArrays.ensureOffsetLength(a, offset, length);
for (int i = 0; i < length; i++)
add(a[offset + i]);
}
/**
* Creates a new hash set with {@link Hash#DEFAULT_LOAD_FACTOR} as load factor
* and fills it with the elements of a given array.
*
* @param a
* an array whose elements will be used to fill the set.
* @param offset
* the first element to use.
* @param length
* the number of elements to use.
*/
public ShortOpenHashSet(final short[] a, final int offset, final int length) {
this(a, offset, length, DEFAULT_LOAD_FACTOR);
}
/**
* Creates a new hash set copying the elements of an array.
*
* @param a
* an array to be copied into the new hash set.
* @param f
* the load factor.
*/
public ShortOpenHashSet(final short[] a, final float f) {
this(a, 0, a.length, f);
}
/**
* Creates a new hash set with {@link Hash#DEFAULT_LOAD_FACTOR} as load factor
* copying the elements of an array.
*
* @param a
* an array to be copied into the new hash set.
*/
public ShortOpenHashSet(final short[] a) {
this(a, DEFAULT_LOAD_FACTOR);
}
private int realSize() {
return containsNull ? size - 1 : size;
}
private void ensureCapacity(final int capacity) {
final int needed = arraySize(capacity, f);
if (needed > n)
rehash(needed);
}
private void tryCapacity(final long capacity) {
final int needed = (int) Math.min(1 << 30,
Math.max(2, HashCommon.nextPowerOfTwo((long) Math.ceil(capacity / f))));
if (needed > n)
rehash(needed);
}
@Override
public boolean addAll(ShortCollection c) {
if (f <= .5)
ensureCapacity(c.size()); // The resulting collection will be sized for c.size() elements
else
tryCapacity(size() + c.size()); // The resulting collection will be tentatively sized for size() + c.size()
// elements
return super.addAll(c);
}
@Override
public boolean addAll(Collection c) {
// The resulting collection will be at least c.size() big
if (f <= .5)
ensureCapacity(c.size()); // The resulting collection will be sized for c.size() elements
else
tryCapacity(size() + c.size()); // The resulting collection will be tentatively sized for size() + c.size()
// elements
return super.addAll(c);
}
@Override
public boolean add(final short k) {
int pos;
if (((k) == ((short) 0))) {
if (containsNull)
return false;
containsNull = true;
} else {
short curr;
final short[] key = this.key;
// The starting point.
if (!((curr = key[pos = (it.unimi.dsi.fastutil.HashCommon.mix((k))) & mask]) == ((short) 0))) {
if (((curr) == (k)))
return false;
while (!((curr = key[pos = (pos + 1) & mask]) == ((short) 0)))
if (((curr) == (k)))
return false;
}
key[pos] = k;
}
if (size++ >= maxFill)
rehash(arraySize(size + 1, f));
if (ASSERTS)
checkTable();
return true;
}
/**
* Shifts left entries with the specified hash code, starting at the specified
* position, and empties the resulting free entry.
*
* @param pos
* a starting position.
*/
protected final void shiftKeys(int pos) {
// Shift entries with the same hash.
int last, slot;
short curr;
final short[] key = this.key;
for (;;) {
pos = ((last = pos) + 1) & mask;
for (;;) {
if (((curr = key[pos]) == ((short) 0))) {
key[last] = ((short) 0);
return;
}
slot = (it.unimi.dsi.fastutil.HashCommon.mix((curr))) & mask;
if (last <= pos ? last >= slot || slot > pos : last >= slot && slot > pos)
break;
pos = (pos + 1) & mask;
}
key[last] = curr;
}
}
private boolean removeEntry(final int pos) {
size--;
shiftKeys(pos);
if (n > minN && size < maxFill / 4 && n > DEFAULT_INITIAL_SIZE)
rehash(n / 2);
return true;
}
private boolean removeNullEntry() {
containsNull = false;
key[n] = ((short) 0);
size--;
if (n > minN && size < maxFill / 4 && n > DEFAULT_INITIAL_SIZE)
rehash(n / 2);
return true;
}
@Override
public boolean remove(final short k) {
if (((k) == ((short) 0))) {
if (containsNull)
return removeNullEntry();
return false;
}
short curr;
final short[] key = this.key;
int pos;
// The starting point.
if (((curr = key[pos = (it.unimi.dsi.fastutil.HashCommon.mix((k))) & mask]) == ((short) 0)))
return false;
if (((k) == (curr)))
return removeEntry(pos);
while (true) {
if (((curr = key[pos = (pos + 1) & mask]) == ((short) 0)))
return false;
if (((k) == (curr)))
return removeEntry(pos);
}
}
@Override
public boolean contains(final short k) {
if (((k) == ((short) 0)))
return containsNull;
short curr;
final short[] key = this.key;
int pos;
// The starting point.
if (((curr = key[pos = (it.unimi.dsi.fastutil.HashCommon.mix((k))) & mask]) == ((short) 0)))
return false;
if (((k) == (curr)))
return true;
while (true) {
if (((curr = key[pos = (pos + 1) & mask]) == ((short) 0)))
return false;
if (((k) == (curr)))
return true;
}
}
/*
* Removes all elements from this set.
*
*
To increase object reuse, this method does not change the table size. If
* you want to reduce the table size, you must use {@link #trim()}.
*
*/
@Override
public void clear() {
if (size == 0)
return;
size = 0;
containsNull = false;
Arrays.fill(key, ((short) 0));
}
@Override
public int size() {
return size;
}
@Override
public boolean isEmpty() {
return size == 0;
}
/** An iterator over a hash set. */
private class SetIterator implements ShortIterator {
/**
* The index of the last entry returned, if positive or zero; initially,
* {@link #n}. If negative, the last element returned was that of index
* {@code - pos - 1} from the {@link #wrapped} list.
*/
int pos = n;
/**
* The index of the last entry that has been returned (more precisely, the value
* of {@link #pos} if {@link #pos} is positive, or {@link Integer#MIN_VALUE} if
* {@link #pos} is negative). It is -1 if either we did not return an entry yet,
* or the last returned entry has been removed.
*/
int last = -1;
/** A downward counter measuring how many entries must still be returned. */
int c = size;
/** A boolean telling us whether we should return the null key. */
boolean mustReturnNull = ShortOpenHashSet.this.containsNull;
/**
* A lazily allocated list containing elements that have wrapped around the
* table because of removals.
*/
ShortArrayList wrapped;
@Override
public boolean hasNext() {
return c != 0;
}
@Override
public short nextShort() {
if (!hasNext())
throw new NoSuchElementException();
c--;
if (mustReturnNull) {
mustReturnNull = false;
last = n;
return key[n];
}
final short key[] = ShortOpenHashSet.this.key;
for (;;) {
if (--pos < 0) {
// We are just enumerating elements from the wrapped list.
last = Integer.MIN_VALUE;
return wrapped.getShort(-pos - 1);
}
if (!((key[pos]) == ((short) 0)))
return key[last = pos];
}
}
/**
* Shifts left entries with the specified hash code, starting at the specified
* position, and empties the resulting free entry.
*
* @param pos
* a starting position.
*/
private final void shiftKeys(int pos) {
// Shift entries with the same hash.
int last, slot;
short curr;
final short[] key = ShortOpenHashSet.this.key;
for (;;) {
pos = ((last = pos) + 1) & mask;
for (;;) {
if (((curr = key[pos]) == ((short) 0))) {
key[last] = ((short) 0);
return;
}
slot = (it.unimi.dsi.fastutil.HashCommon.mix((curr))) & mask;
if (last <= pos ? last >= slot || slot > pos : last >= slot && slot > pos)
break;
pos = (pos + 1) & mask;
}
if (pos < last) { // Wrapped entry.
if (wrapped == null)
wrapped = new ShortArrayList(2);
wrapped.add(key[pos]);
}
key[last] = curr;
}
}
@Override
public void remove() {
if (last == -1)
throw new IllegalStateException();
if (last == n) {
ShortOpenHashSet.this.containsNull = false;
ShortOpenHashSet.this.key[n] = ((short) 0);
} else if (pos >= 0)
shiftKeys(last);
else {
// We're removing wrapped entries.
ShortOpenHashSet.this.remove(wrapped.getShort(-pos - 1));
last = -1; // Note that we must not decrement size
return;
}
size--;
last = -1; // You can no longer remove this entry.
if (ASSERTS)
checkTable();
}
}
@Override
public ShortIterator iterator() {
return new SetIterator();
}
/**
* Rehashes this set, making the table as small as possible.
*
*
* This method rehashes the table to the smallest size satisfying the load
* factor. It can be used when the set will not be changed anymore, so to
* optimize access speed and size.
*
*
* If the table size is already the minimum possible, this method does nothing.
*
* @return true if there was enough memory to trim the set.
* @see #trim(int)
*/
public boolean trim() {
return trim(size);
}
/**
* Rehashes this set if the table is too large.
*
*
* Let N be the smallest table size that can hold
* max(n,{@link #size()}) entries, still satisfying the load
* factor. If the current table size is smaller than or equal to N,
* this method does nothing. Otherwise, it rehashes this set in a table of size
* N.
*
*
* This method is useful when reusing sets. {@linkplain #clear() Clearing a set}
* leaves the table size untouched. If you are reusing a set many times, you can
* call this method with a typical size to avoid keeping around a very large
* table just because of a few large transient sets.
*
* @param n
* the threshold for the trimming.
* @return true if there was enough memory to trim the set.
* @see #trim()
*/
public boolean trim(final int n) {
final int l = HashCommon.nextPowerOfTwo((int) Math.ceil(n / f));
if (l >= this.n || size > maxFill(l, f))
return true;
try {
rehash(l);
} catch (OutOfMemoryError cantDoIt) {
return false;
}
return true;
}
/**
* Rehashes the set.
*
*
* This method implements the basic rehashing strategy, and may be overriden by
* subclasses implementing different rehashing strategies (e.g., disk-based
* rehashing). However, you should not override this method unless you
* understand the internal workings of this class.
*
* @param newN
* the new size
*/
protected void rehash(final int newN) {
final short key[] = this.key;
final int mask = newN - 1; // Note that this is used by the hashing macro
final short newKey[] = new short[newN + 1];
int i = n, pos;
for (int j = realSize(); j-- != 0;) {
while (((key[--i]) == ((short) 0)));
if (!((newKey[pos = (it.unimi.dsi.fastutil.HashCommon.mix((key[i]))) & mask]) == ((short) 0)))
while (!((newKey[pos = (pos + 1) & mask]) == ((short) 0)));
newKey[pos] = key[i];
}
n = newN;
this.mask = mask;
maxFill = maxFill(n, f);
this.key = newKey;
}
/**
* Returns a deep copy of this set.
*
*
* This method performs a deep copy of this hash set; the data stored in the
* set, however, is not cloned. Note that this makes a difference only for
* object keys.
*
* @return a deep copy of this set.
*/
@Override
public ShortOpenHashSet clone() {
ShortOpenHashSet c;
try {
c = (ShortOpenHashSet) super.clone();
} catch (CloneNotSupportedException cantHappen) {
throw new InternalError();
}
c.key = key.clone();
c.containsNull = containsNull;
return c;
}
/**
* Returns a hash code for this set.
*
* This method overrides the generic method provided by the superclass. Since
* {@code equals()} is not overriden, it is important that the value returned by
* this method is the same value as the one returned by the overriden method.
*
* @return a hash code for this set.
*/
@Override
public int hashCode() {
int h = 0;
for (int j = realSize(), i = 0; j-- != 0;) {
while (((key[i]) == ((short) 0)))
i++;
h += (key[i]);
i++;
}
// Zero / null have hash zero.
return h;
}
private void writeObject(java.io.ObjectOutputStream s) throws java.io.IOException {
final ShortIterator i = iterator();
s.defaultWriteObject();
for (int j = size; j-- != 0;)
s.writeShort(i.nextShort());
}
private void readObject(java.io.ObjectInputStream s) throws java.io.IOException, ClassNotFoundException {
s.defaultReadObject();
n = arraySize(size, f);
maxFill = maxFill(n, f);
mask = n - 1;
final short key[] = this.key = new short[n + 1];
short k;
for (int i = size, pos; i-- != 0;) {
k = s.readShort();
if (((k) == ((short) 0))) {
pos = n;
containsNull = true;
} else {
if (!((key[pos = (it.unimi.dsi.fastutil.HashCommon.mix((k))) & mask]) == ((short) 0)))
while (!((key[pos = (pos + 1) & mask]) == ((short) 0)));
}
key[pos] = k;
}
if (ASSERTS)
checkTable();
}
private void checkTable() {
}
}