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add random
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9 files changed

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‎build.gradle‎

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@@ -26,7 +26,7 @@ tasks.withType(JavaCompile) { options.encoding = "UTF-8" }
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group = 'com.github.myibu'
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archivesBaseName = "algorithm-java"
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version = "1.0.0"
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version = "1.0.0a"
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repositories {
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mavenCentral()

‎docs/LinearCongruence.pdf‎

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‎docs/MersenneTwister.pdf‎

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‎readme.md‎

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@@ -28,12 +28,18 @@ Reference to: [BloomFilter.pdf](./docs/BloomFilter.pdf)
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| rShift | `>>` |
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| rrShift | `>>>` |
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### LinearCongruentialRandom
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Reference to: [LinearCongruence.pdf](./docs/LinearCongruence.pdf)
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### MersenneTwisterRandom
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Reference to: [MersenneTwister.pdf](./docs/MersenneTwister.pdf)
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## Installation
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```bash
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<dependency>
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<groupId>com.github.myibu</groupId>
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<artifactId>algorithm-java</artifactId>
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<version>1.0.0</version>
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<version>1.0.0a</version>
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</dependency>
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```
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‎src/main/java/com/github/myibu/algorithm/random/LinearCongruentialRandom.java‎

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package com.github.myibu.algorithm.random;
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import java.util.concurrent.atomic.AtomicLong;
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/**
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* Linear Congruence method for generating Pseudo Random Numbers
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* Copy from "java.util.Random"
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* @author myibu
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* Created on 2021/9/17
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*/
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public class LinearCongruentialRandom implements Random {
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static final String BadBound = "bound must be positive";
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static final String BadRange = "bound must be greater than origin";
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static final String BadSize = "size must be non-negative";
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private final AtomicLong seed;
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private static final long multiplier = 0x5DEECE66DL;
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private static final long addend = 0xBL;
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private static final long mask = (1L << 48) - 1;
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private static final double DOUBLE_UNIT = 0x1.0p-53; // 1.0 / (1L << 53)
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public LinearCongruentialRandom() {
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this(seedUniquifier() ^ System.nanoTime());
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}
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private static long seedUniquifier() {
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for (;;) {
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long current = seedUniquifier.get();
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long next = current * 1181783497276652981L;
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if (seedUniquifier.compareAndSet(current, next))
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return next;
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}
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}
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private static final AtomicLong seedUniquifier
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= new AtomicLong(8682522807148012L);
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public LinearCongruentialRandom(long seed) {
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this.seed = new AtomicLong(initialScramble(seed));
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}
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private static long initialScramble(long seed) {
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return (seed ^ multiplier) & mask;
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}
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public synchronized void setSeed(long seed) {
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this.seed.set(initialScramble(seed));
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}
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public int next(int bits) {
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long oldseed, nextseed;
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AtomicLong seed = this.seed;
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do {
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oldseed = seed.get();
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nextseed = (oldseed * multiplier + addend) & mask;
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} while (!seed.compareAndSet(oldseed, nextseed));
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return (int)(nextseed >>> (48 - bits));
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}
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@Override
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public void nextBytes(byte[] bytes) {
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for (int i = 0, len = bytes.length; i < len; )
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for (int rnd = nextInt(),
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n = Math.min(len - i, Integer.SIZE/Byte.SIZE);
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n-- > 0; rnd >>= Byte.SIZE)
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bytes[i++] = (byte)rnd;
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}
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@Override
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public int nextInt() {
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return next(32);
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}
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@Override
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public int nextInt(int bound) {
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if (bound <= 0)
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throw new IllegalArgumentException(BadBound);
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int r = next(31);
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int m = bound - 1;
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if ((bound & m) == 0) // i.e., bound is a power of 2
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r = (int)((bound * (long)r) >> 31);
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else {
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for (int u = r;
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u - (r = u % bound) + m < 0;
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u = next(31))
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;
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}
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return r;
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}
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@Override
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public long nextLong() {
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return ((long)(next(32)) << 32) + next(32);
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}
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public boolean nextBoolean() {
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return next(1) != 0;
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}
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@Override
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public float nextFloat() {
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return next(24) / ((float)(1 << 24));
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}
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@Override
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public double nextDouble() {
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return (((long)(next(26)) << 27) + next(27)) * DOUBLE_UNIT;
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}
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}

‎src/main/java/com/github/myibu/algorithm/random/MersenneTwisterRandom.java‎

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package com.github.myibu.algorithm.random;
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import java.util.concurrent.atomic.AtomicLong;
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/**
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* Mersenne Twister method for generating Pseudo Random Numbers
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* MT19937
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* @author myibu
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* Created on 2021/9/17
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*/
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public class MersenneTwisterRandom implements Random {
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static final int MT19937_SIZE = 624; // 624 * 32 - 31 = 19937
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static final String BadBound = "bound must be positive";
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private static final double DOUBLE_UNIT = 0x1.0p-53; // 1.0 / (1L << 53)
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private final long seed;
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private long[] mt;
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public MersenneTwisterRandom() {
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this((int)(seedUniquifier() ^ System.nanoTime()));
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}
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public MersenneTwisterRandom(long seed) {
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this.seed = seed;
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this.mt = new long[MT19937_SIZE];
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mt[0] = seed;
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for (int i = 1; i < MT19937_SIZE; i++) {
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mt[i] = 1812433253L * (mt[i-1] ^ (mt[i-1] >> 30)) + i;
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}
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}
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private static long seedUniquifier() {
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for (;;) {
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long current = seedUniquifier.get();
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long next = current * 1181783497276652981L;
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if (seedUniquifier.compareAndSet(current, next))
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return next;
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}
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}
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private static final AtomicLong seedUniquifier
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= new AtomicLong(8682522807148012L);
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private void generate() {
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for (int i = 0; i < MT19937_SIZE; i++) {
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// 2^31 = 0x80000000, 2^31-1 = 0x7fffffff
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long y = (mt[i] & 0x80000000L) + (mt[(i+1) % 624] & 0x7fffffffL);
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mt[i] = mt[(i + 397) % 624] ^ (y >> 1);
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if ((y & 1) != 0)
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mt[i] ^= 0x9908b0dfL;
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}
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}
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@Override
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public void nextBytes(byte[] bytes) {
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for (int i = 0, len = bytes.length; i < len; )
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for (int rnd = nextInt(),
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n = Math.min(len - i, Integer.SIZE/Byte.SIZE);
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n-- > 0; rnd >>= Byte.SIZE)
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bytes[i++] = (byte)rnd;
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}
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@Override
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public int nextInt() {
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generate();
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long y = mt[0];
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y = y ^ (y >> 11);
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y = y ^ ((y << 7) & 2636928640L);
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y = y ^ ((y << 15) & 4022730752L);
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y = y ^ (y >> 18);
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return (int)y;
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}
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@Override
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public int nextInt(int bound) {
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if (bound <= 0)
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throw new IllegalArgumentException(BadBound);
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int r = nextInt();
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int m = bound - 1;
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if ((bound & m) == 0) // i.e., bound is a power of 2
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r = (int)((bound * (long)r) >> 31);
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else {
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for (int u = r;
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u - (r = u % bound) + m < 0;
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u = nextInt())
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;
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}
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return r;
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}
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@Override
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public long nextLong() {
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return ((long)(nextInt()) << 32) + nextInt();
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}
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@Override
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public boolean nextBoolean() {
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return (nextInt() & 0x00000001) != 0;
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}
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@Override
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public float nextFloat() {
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return nextInt() / ((float)(1 << 24));
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}
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@Override
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public double nextDouble() {
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return (((long)(nextInt()) << 27) + nextInt()) * DOUBLE_UNIT;
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}
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}

‎src/main/java/com/github/myibu/algorithm/random/Random.java‎

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package com.github.myibu.algorithm.random;
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/**
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* random interface
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* @author myibu
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* Created on 2021/9/17
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*/
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public interface Random {
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void nextBytes(byte[] bytes);
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int nextInt();
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int nextInt(int bound);
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long nextLong();
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boolean nextBoolean();
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float nextFloat();
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double nextDouble();
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}

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