Package it.unimi.dsi.sux4j.mph

Class VLLcpMonotoneMinimalPerfectHashFunction<T>

java.lang.Object

it.unimi.dsi.fastutil.objects.AbstractObject2LongFunction<K>

it.unimi.dsi.sux4j.mph.AbstractHashFunction<T>

it.unimi.dsi.sux4j.mph.VLLcpMonotoneMinimalPerfectHashFunction<T>

All Implemented Interfaces:

Function<T,Long>, Object2LongFunction<T>, Size64, Serializable, Function<T,Long>, ToLongFunction<T>

public class VLLcpMonotoneMinimalPerfectHashFunction<T>
extends AbstractHashFunction<T>
implements Serializable, Size64

A monotone minimal perfect hash implementation based on fixed-size bucketing that uses longest common prefixes as distributors, and store their lengths using a GOVMinimalPerfectHashFunction indexing an EliasFanoLongBigList. In theory, this function should use less memory than an LcpMonotoneMinimalPerfectHashFunction when the lengths of common prefixes vary wildly, but in practice a TwoStepsLcpMonotoneMinimalPerfectHashFunction is often a better choice.

See Also:

• Serialized Form

Field Summary

Fields

Modifier and Type	Field	Description
protected final int	bucketSize	The size of a bucket.
protected final int	bucketSizeMask	The mask for log2BucketSize bits.
protected final GOV3Function<BitVector>	lcp2Bucket	A function mapping each longest common prefix to its bucket.
protected final EliasFanoLongBigList	lcpLengths	A list, indexed by mph, containing for each element the length of the longest common prefix of its bucket.
protected final int	log2BucketSize	Fast.ceilLog2(int) of bucketSize.
protected final GOVMinimalPerfectHashFunction<BitVector>	mph	A function mapping each element to a distinct index.
protected final long	n	The number of elements.
protected final LongBigList	offsets	A list, indexed by mph, containing the offset of each element inside its bucket.
static final long	serialVersionUID
protected final TransformationStrategy<? super T>	transform	The transformation strategy.

Fields inherited from class it.unimi.dsi.fastutil.objects.AbstractObject2LongFunction

defRetValue

Constructor Summary

Constructors

Constructor	Description
VLLcpMonotoneMinimalPerfectHashFunction(Iterable<? extends T> iterable, int numElements, TransformationStrategy<? super T> transform)
VLLcpMonotoneMinimalPerfectHashFunction(Iterable<? extends T> iterable, TransformationStrategy<? super T> transform)

Method Summary

Modifier and Type	Method	Description
long	getLong(Object o)
static void	main(String[] arg)
long	numBits()	Returns the number of bits used by this structure.
long	size64()

Methods inherited from class it.unimi.dsi.sux4j.mph.AbstractHashFunction

containsKey, size

Methods inherited from class it.unimi.dsi.fastutil.objects.AbstractObject2LongFunction

defaultReturnValue, defaultReturnValue

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface it.unimi.dsi.fastutil.Function

apply, clear

Methods inherited from interface java.util.function.Function

compose

Methods inherited from interface it.unimi.dsi.fastutil.objects.Object2LongFunction

andThen, andThenByte, andThenChar, andThenDouble, andThenFloat, andThenInt, andThenLong, andThenObject, andThenReference, andThenShort, applyAsLong, composeByte, composeChar, composeDouble, composeFloat, composeInt, composeLong, composeObject, composeReference, composeShort, get, getOrDefault, getOrDefault, put, put, remove, removeLong

Methods inherited from interface it.unimi.dsi.fastutil.Size64

size

Field Details

serialVersionUID

public static final long serialVersionUID

See Also:

• Constant Field Values

n

protected final long n

The number of elements.

bucketSize

protected final int bucketSize

The size of a bucket.

log2BucketSize

protected final int log2BucketSize

Fast.ceilLog2(int) of bucketSize.

bucketSizeMask

protected final int bucketSizeMask

The mask for log2BucketSize bits.

mph

protected final GOVMinimalPerfectHashFunction<BitVector> mph

A function mapping each element to a distinct index.

offsets

protected final LongBigList offsets

A list, indexed by mph, containing the offset of each element inside its bucket.

lcpLengths

protected final EliasFanoLongBigList lcpLengths

A list, indexed by mph, containing for each element the length of the longest common prefix of its bucket.

lcp2Bucket

protected final GOV3Function<BitVector> lcp2Bucket

A function mapping each longest common prefix to its bucket.

transform

protected final TransformationStrategy<? super T> transform

The transformation strategy.

Constructor Details

VLLcpMonotoneMinimalPerfectHashFunction

public VLLcpMonotoneMinimalPerfectHashFunction(Iterable<? extends T> iterable,
 TransformationStrategy<? super T> transform)
                                        throws IOException

Throws:

IOException

VLLcpMonotoneMinimalPerfectHashFunction

public VLLcpMonotoneMinimalPerfectHashFunction(Iterable<? extends T> iterable,
 int numElements,
 TransformationStrategy<? super T> transform)
                                        throws IOException

Throws:

IOException

Method Details

getLong

public long getLong(Object o)

Specified by:

getLong in interface Object2LongFunction<T>

size64

public long size64()

Specified by:

size64 in interface Size64

Overrides:

size64 in class AbstractHashFunction<T>

numBits

public long numBits()

Returns the number of bits used by this structure.

Returns:

the number of bits used by this structure.

main

public static void main(String[] arg)
                 throws NoSuchMethodException,
IOException,
JSAPException

Throws:

NoSuchMethodException

IOException

JSAPException