Package it.unimi.dsi.sux4j.mph

Class TwoStepsLcpMonotoneMinimalPerfectHashFunction<T>

java.lang.Object

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

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

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

All Implemented Interfaces:

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

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

A monotone minimal perfect hash implementation based on fixed-size bucketing that uses longest common prefixes as distributors, and store their lengths using a TwoStepsGOV3Function.

This implementation should use a few less bits per elements than LcpMonotoneMinimalPerfectHashFunction, but it is a bit slower as one or two additional functions must be queried.

See the package overview for a comparison with other implementations. Similarly to a GOV3Function, an instance of this class may be signed.

See Also:

• Serialized Form

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static class	TwoStepsLcpMonotoneMinimalPerfectHashFunction.Builder<T>	A builder class for TwoStepsLcpMonotoneMinimalPerfectHashFunction.

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 TwoStepsGOV3Function<BitVector>	lcpLengths	A function mapping each element to the length of the longest common prefix of its bucket.
protected final int	log2BucketSize	Fast.ceilLog2(int) of bucketSize.
protected final long	n	The number of elements.
protected final GOV3Function<BitVector>	offsets	A function mapping each element to the offset inside its bucket.
protected final long	seed	The seed returned by the BucketedHashStore.
static final long	serialVersionUID
protected final long	signatureMask	The mask to compare signatures, or zero for no signatures.
protected final LongBigList	signatures	The signatures.
protected final TransformationStrategy<? super T>	transform	The transformation strategy.

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

defRetValue

Constructor Summary

Constructors

Modifier	Constructor	Description
protected	TwoStepsLcpMonotoneMinimalPerfectHashFunction(Iterable<? extends T> keys, long numKeys, TransformationStrategy<? super T> transform, int signatureWidth, File tempDir)	Creates a new two-steps LCP monotone minimal perfect hash function for the given keys.

Method Summary

Modifier and Type	Method	Description
long	getLong(Object o)
long	getLongByBitVectorAndSignature(BitVector bitVector, long[] signature)
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.

offsets

protected final GOV3Function<BitVector> offsets

A function mapping each element to the offset inside its bucket.

lcpLengths

protected final TwoStepsGOV3Function<BitVector> lcpLengths

A function mapping each element to 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.

seed

protected final long seed

The seed returned by the BucketedHashStore.

signatureMask

protected final long signatureMask

The mask to compare signatures, or zero for no signatures.

signatures

protected final LongBigList signatures

The signatures.

Constructor Details

TwoStepsLcpMonotoneMinimalPerfectHashFunction

protected TwoStepsLcpMonotoneMinimalPerfectHashFunction(Iterable<? extends T> keys,
 long numKeys,
 TransformationStrategy<? super T> transform,
 int signatureWidth,
 File tempDir)
                                                 throws IOException

Creates a new two-steps LCP monotone minimal perfect hash function for the given keys.

Parameters:

keys - the keys to hash.

numKeys - the number of keys, or -1 if the number of keys is not known (will be computed).

transform - a transformation strategy for the keys.

signatureWidth - a signature width, or 0 for no signature.

tempDir - a temporary directory for the store files, or null for the standard temporary directory.

Throws:

IOException

Method Details

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.

getLong

public long getLong(Object o)

Specified by:

getLong in interface Object2LongFunction<T>

getLongByBitVectorAndSignature

public long getLongByBitVectorAndSignature(BitVector bitVector,
 long[] signature)

main

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

Throws:

NoSuchMethodException

IOException

JSAPException