com.carrotsearch.hppcrt.hash

Class PhiMix

java.lang.Object

com.carrotsearch.hppcrt.hash.PhiMix

public final class PhiMix
extends java.lang.Object

Quickly mixes the bits of integers.

Those methods mixes the bits of the argument by multiplying by the golden ratio and xorshifting the result.

It is borrowed from Koloboke, and it has slightly worse behaviour than MurmurHash3 (in open-addressing hash tables the average number of probes is slightly larger), but it's much faster.

Reciprocal mixing functions are borrowed from fastutil.

Field Summary

Fields

Modifier and Type	Field and Description
static int	HASH_0 = hash((int)0)
static int	HASH_1 = hash((int)1)

Method Summary

Modifier and Type	Method and Description
static int	invMix32(int x) The inverse of mix32(int).
static long	invMix64(long x) The inverse of mix64(long).
static int	mix32(int x) Hashes a 4-byte sequence (Java int).
static long	mix64(long x) Hashes an 8-byte sequence (Java long).

Methods inherited from class java.lang.Object

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

Field Detail

HASH_0

public static final int HASH_0

= hash((int)0)

See Also:

Constant Field Values

HASH_1

public static final int HASH_1

= hash((int)1)

See Also:

Constant Field Values

Method Detail

mix32

public static int mix32(int x)

Hashes a 4-byte sequence (Java int).

Parameters:

x - an integer.

Returns:

a hash value obtained by mixing the bits of x.

invMix32

public static int invMix32(int x)

The inverse of mix32(int). This method is mainly useful to create unit tests.

Parameters:

x - an integer.

Returns:

a value that passed through mix32(int) would give x .

mix64

public static long mix64(long x)

Hashes an 8-byte sequence (Java long).

Parameters:

x - a long integer.

Returns:

a hash value obtained by mixing the bits of x.

invMix64

public static long invMix64(long x)

The inverse of mix64(long). This method is mainly useful to create unit tests.

Parameters:

x - a long integer.

Returns:

a value that passed through mix64(long) would give x.