com.uwyn.jhighlight.fastutil

クラス HashCommon

java.lang.Object

com.uwyn.jhighlight.fastutil.HashCommon

public class HashCommon
extends Object

Common code for all hash-based classes.

フィールドの概要

フィールド

修飾子とタイプ	フィールドと説明
static Object	REMOVED This reference is used to fill keys and values of removed entries (if they are objects).

コンストラクタの概要

コンストラクタ

修飾子	コンストラクタと説明
protected	HashCommon()

メソッドの概要

メソッド

修飾子とタイプ	メソッドと説明
static int	arraySize(int expected, float f) Returns the least power of two smaller than or equal to 230 and larger than or equal to Math.ceil( expected / f ).
static long	bigArraySize(long expected, float f) Returns the least power of two larger than or equal to Math.ceil( expected / f ).
static int	double2int(double d) Returns the hash code that would be returned by Double.hashCode().
static int	float2int(float f) Returns the hash code that would be returned by Float.hashCode().
static int	long2int(long l) Returns the hash code that would be returned by Long.hashCode().
static int	maxFill(int n, float f) Returns the maximum number of entries that can be filled before rehashing.
static long	maxFill(long n, float f) Returns the maximum number of entries that can be filled before rehashing.
static int	murmurHash3(int x) Avalanches the bits of an integer by applying the finalisation step of MurmurHash3.
static long	murmurHash3(long x) Avalanches the bits of a long integer by applying the finalisation step of MurmurHash3.
static int	nextPowerOfTwo(int x) Return the least power of two greater than or equal to the specified value.
static long	nextPowerOfTwo(long x) Return the least power of two greater than or equal to the specified value.

クラスから継承されたメソッド java.lang.Object

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

フィールドの詳細

REMOVED

public static final Object REMOVED

This reference is used to fill keys and values of removed entries (if they are objects). null cannot be used as it would confuse the search algorithm in the presence of an actual null key.

コンストラクタの詳細

HashCommon

protected HashCommon()

メソッドの詳細

murmurHash3

public static final int murmurHash3(int x)

Avalanches the bits of an integer by applying the finalisation step of MurmurHash3.

This method implements the finalisation step of Austin Appleby's MurmurHash3. Its purpose is to avalanche the bits of the argument to within 0.25% bias. It is used, among other things, to scramble quickly (but deeply) the hash values returned by Object.hashCode().

パラメータ:

x - an integer.

戻り値:

a hash value with good avalanching properties.

murmurHash3

public static final long murmurHash3(long x)

Avalanches the bits of a long integer by applying the finalisation step of MurmurHash3.

This method implements the finalisation step of Austin Appleby's MurmurHash3. Its purpose is to avalanche the bits of the argument to within 0.25% bias. It is used, among other things, to scramble quickly (but deeply) the hash values returned by Object.hashCode().

Incidentally, iterating this method starting from a nonzero value will generate a sequence of nonzero values that passes strongest statistical tests.

パラメータ:

x - a long integer.

戻り値:

a hash value with good avalanching properties.

float2int

public static final int float2int(float f)

Returns the hash code that would be returned by Float.hashCode().

戻り値:

the same code as new Float(f).hashCode().

double2int

public static final int double2int(double d)

Returns the hash code that would be returned by Double.hashCode().

戻り値:

the same code as new Double(f).hashCode().

long2int

public static final int long2int(long l)

Returns the hash code that would be returned by Long.hashCode().

戻り値:

the same code as new Long(f).hashCode().

nextPowerOfTwo

public static int nextPowerOfTwo(int x)

Return the least power of two greater than or equal to the specified value.

Note that this function will return 1 when the argument is 0.

パラメータ:

x - an integer smaller than or equal to 2³⁰.

戻り値:

the least power of two greater than or equal to the specified value.

nextPowerOfTwo

public static long nextPowerOfTwo(long x)

Return the least power of two greater than or equal to the specified value.

Note that this function will return 1 when the argument is 0.

パラメータ:

x - a long integer smaller than or equal to 2⁶².

戻り値:

the least power of two greater than or equal to the specified value.

maxFill

public static int maxFill(int n,
          float f)

Returns the maximum number of entries that can be filled before rehashing.

パラメータ:

n - the size of the backing array.

f - the load factor.

戻り値:

the maximum number of entries before rehashing.

maxFill

public static long maxFill(long n,
           float f)

Returns the maximum number of entries that can be filled before rehashing.

パラメータ:

n - the size of the backing array.

f - the load factor.

戻り値:

the maximum number of entries before rehashing.

arraySize

public static int arraySize(int expected,
            float f)

Returns the least power of two smaller than or equal to 2³⁰ and larger than or equal to Math.ceil( expected / f ).

パラメータ:

expected - the expected number of elements in a hash table.

f - the load factor.

戻り値:

the minimum possible size for a backing array.

例外:

IllegalArgumentException - if the necessary size is larger than 2³⁰.

bigArraySize

public static long bigArraySize(long expected,
                float f)

Returns the least power of two larger than or equal to Math.ceil( expected / f ).

パラメータ:

expected - the expected number of elements in a hash table.

f - the load factor.

戻り値:

the minimum possible size for a backing big array.