jdd.util

Class Array

java.lang.Object

jdd.util.Array

public final class Array
extends Object

some common operations involving arrays has been gathered here. The idea is to concenterate all loops in the same class so it can be optimized by the JVM (loop unrolloing, SIMD etc).

we used to have all the loops unrolled here, but it turns out that the latest JVMs (1.4.2_02 and above) do a much better job.

Constructor Summary

Constructors

Constructor and Description
Array()

Method Summary

Modifier and Type	Method and Description
static boolean[]	clone(boolean[] old)
static int[]	clone(int[] old) cone an array of integers and its members
static void	copy(int[] from, int[] to, int len, int from_offset, int to_offset) a fast (?) function for copying chunks of an array to another (possibly same) array.
static int	count(boolean[] x, boolean val) count the number of times val is seen in the array x
static int	count(int[] x, int val) count the number of times val is seen in the array x
static void	disturb(int[] x, int len) disturb the current order, but not a full shuffle (to save time)
static boolean	equals(boolean[] v1, boolean[] v2, int len) compare to vectors
static boolean	equals(byte[] v1, byte[] v2, int len) compare to vectors
static boolean	equals(int[] v1, int[] v2, int len) compare to vectors
static boolean	equals(short[] v1, short[] v2, int len) compare to vectors
static void	internal_test() testbench.
static int[]	permutation(int size) create a permutation from {0, ...
static int[]	resize(int[] old, int old_size, int new_size) this is an implementation of realloc() for integers.
static short[]	resize(short[] old, int old_size, int new_size) this is an implementation of realloc() for short integers.
static void	reverse(double[] variables, int size) reverse an array of doubles
static void	reverse(int[] variables, int size) reverse an array of ints
static void	reverse(Object[] variables, int size) reverse some list
static void	set(boolean[] x, boolean val) set the members of the array x to val
static void	set(int[] x, int val) set the elements of "x" to "val" (faster than for(...) x[i] = val; )
static void	set(int[] x, int val, int length) set the first "length" elements of "x" to "val" (faster than for(...) x[i] = val; )
static void	shuffle(int[] x) shuffle the members of an array
static void	shuffle(int[] x, int len) shuffle the first len members of an array

Methods inherited from class java.lang.Object

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

Constructor Detail

Array

public Array()

Method Detail

resize

public static final int[] resize(int[] old,
                                 int old_size,
                                 int new_size)

this is an implementation of realloc() for integers. the old_size old members are copied to the new array

resize

public static final short[] resize(short[] old,
                                   int old_size,
                                   int new_size)

this is an implementation of realloc() for short integers. the old_size old members are copied to the new array

copy

public static final void copy(int[] from,
                              int[] to,
                              int len,
                              int from_offset,
                              int to_offset)

a fast (?) function for copying chunks of an array to another (possibly same) array.

BEWRAE: stupid System.arraycopy() cant hande overlapping arrays correctly

clone

public static final int[] clone(int[] old)

cone an array of integers and its members

clone

public static final boolean[] clone(boolean[] old)

set

public static final void set(int[] x,
                             int val)

set the elements of "x" to "val" (faster than for(...) x[i] = val; )

set

public static final void set(int[] x,
                             int val,
                             int length)

set the first "length" elements of "x" to "val" (faster than for(...) x[i] = val; )

set

public static final void set(boolean[] x,
                             boolean val)

set the members of the array x to val

count

public static final int count(int[] x,
                              int val)

count the number of times val is seen in the array x

count

public static final int count(boolean[] x,
                              boolean val)

count the number of times val is seen in the array x

reverse

public static void reverse(Object[] variables,
                           int size)

reverse some list

reverse

public static void reverse(int[] variables,
                           int size)

reverse an array of ints

reverse

public static void reverse(double[] variables,
                           int size)

reverse an array of doubles

shuffle

public static final void shuffle(int[] x)

shuffle the members of an array

shuffle

public static final void shuffle(int[] x,
                                 int len)

shuffle the first len members of an array

disturb

public static final void disturb(int[] x,
                                 int len)

disturb the current order, but not a full shuffle (to save time)

See Also:

shuffle(int[], int)

permutation

public static final int[] permutation(int size)

create a permutation from {0, ... , size-1} to {0, ... , size-1}.

equals

public static final boolean equals(boolean[] v1,
                                   boolean[] v2,
                                   int len)

compare to vectors

Returns:

true of the first len members of v1 and v2 are equal

equals

public static final boolean equals(short[] v1,
                                   short[] v2,
                                   int len)

compare to vectors

Returns:

true of the first len members of v1 and v2 are equal

equals

public static final boolean equals(byte[] v1,
                                   byte[] v2,
                                   int len)

compare to vectors

Returns:

true of the first len members of v1 and v2 are equal

equals

public static final boolean equals(int[] v1,
                                   int[] v2,
                                   int len)

compare to vectors

Returns:

true of the first len members of v1 and v2 are equal

internal_test

public static void internal_test()

testbench. do not call