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Diffstat (limited to 'src/main/java/gregtech/api/objects/XSTR.java')
-rw-r--r-- | src/main/java/gregtech/api/objects/XSTR.java | 246 |
1 files changed, 246 insertions, 0 deletions
diff --git a/src/main/java/gregtech/api/objects/XSTR.java b/src/main/java/gregtech/api/objects/XSTR.java new file mode 100644 index 0000000000..33823d3ebd --- /dev/null +++ b/src/main/java/gregtech/api/objects/XSTR.java @@ -0,0 +1,246 @@ +package gregtech.api.objects; + +import java.util.Random; +import java.util.concurrent.atomic.AtomicLong; + +/* + * TODO: Check the validity of the algorithm. + * There is a claim that this particular implementation is not faithful to the articles it links, skewing the + * distribution. + */ +/** + * XSTR - Xorshift ThermiteRandom Modified by Bogdan-G 03.06.2016 version 0.0.4 + * <p> + * A subclass of java.util.random that implements the Xorshift random number generator + * <p> + * - it is 30% faster than the generator from Java's library - it produces random sequences of higher quality than + * java.util.Random - this class also provides a clone() function + * <p> + * Usage: XSRandom rand = new XSRandom(); //Instantiation x = rand.nextInt(); //pull a random number + * <p> + * To use the class in legacy code, you may also instantiate an XSRandom object and assign it to a java.util.Random + * object: java.util.Random rand = new XSRandom(); + * <p> + * for an explanation of the algorithm, see http://demesos.blogspot.com/2011/09/pseudo-random-number-generators.html + * + * @author Wilfried Elmenreich University of Klagenfurt/Lakeside Labs http://www.elmenreich.tk + * <p> + * This code is released under the GNU Lesser General Public License Version 3 + * http://www.gnu.org/licenses/lgpl-3.0.txt + */ +public class XSTR extends Random { + + private static final long serialVersionUID = 6208727693524452904L; + private long seed; + private long last; + private static final long GAMMA = 0x9e3779b97f4a7c15L; + private static final int PROBE_INCREMENT = 0x9e3779b9; + private static final long SEEDER_INCREMENT = 0xbb67ae8584caa73bL; + private static final double DOUBLE_UNIT = 0x1.0p-53; // 1.0 / (1L << 53) + private static final float FLOAT_UNIT = 0x1.0p-24f; // 1.0f / (1 << 24) + private static final AtomicLong seedUniquifier = new AtomicLong(8682522807148012L); + public static final XSTR XSTR_INSTANCE = new XSTR() { + + @Override + public synchronized void setSeed(long seed) { + if (!Thread.currentThread() + .getStackTrace()[2].getClassName() + .equals(Random.class.getName())) + throw new NoSuchMethodError("This is meant to be shared!, leave seed state alone!"); + } + }; + + /* + * MODIFIED BY: Robotia Modification: Implemented Random class seed generator + */ + /** + * Creates a new pseudo random number generator. The seed is initialized to the current time, as if by + * <code>setSeed(System.currentTimeMillis());</code>. + */ + public XSTR() { + this(seedUniquifier() ^ System.nanoTime()); + } + + private static long seedUniquifier() { + // L'Ecuyer, "Tables of Linear Congruential Generators of + // Different Sizes and Good Lattice Structure", 1999 + for (;;) { + long current = seedUniquifier.get(); + long next = current * 181783497276652981L; + if (seedUniquifier.compareAndSet(current, next)) { + return next; + } + } + } + + /** + * Creates a new pseudo random number generator, starting with the specified seed, using + * <code>setSeed(seed);</code>. + * + * @param seed the initial seed + */ + public XSTR(long seed) { + this.seed = seed; + } + + @Override + public boolean nextBoolean() { + return next(1) != 0; + } + + @Override + public double nextDouble() { + return (((long) (next(26)) << 27) + next(27)) * DOUBLE_UNIT; + } + + /** + * Returns the current state of the seed, can be used to clone the object + * + * @return the current seed + */ + public synchronized long getSeed() { + return seed; + } + + /** + * Sets the seed for this pseudo random number generator. As described above, two instances of the same random + * class, starting with the same seed, produce the same results, if the same methods are called. + * + * @param seed the new seed + */ + @Override + public synchronized void setSeed(long seed) { + this.seed = seed; + } + + /** + * @return Returns an XSRandom object with the same state as the original + */ + @Override + public XSTR clone() { + return new XSTR(getSeed()); + } + + /** + * Implementation of George Marsaglia's Xorshift random generator that is 30% faster and better quality than the + * built-in java.util.random. + * + * @param nbits number of bits to shift the result for + * @return a random integer + * @see <a href="https://www.javamex.com/tutorials/random_numbers/xorshift.shtml">the Xorshift article</a> + */ + @Override + public int next(int nbits) { + long x = seed; + x ^= (x << 21); + x ^= (x >>> 35); + x ^= (x << 4); + seed = x; + x &= ((1L << nbits) - 1); + return (int) x; + } + + boolean haveNextNextGaussian = false; + double nextNextGaussian = 0; + + @Override + public synchronized double nextGaussian() { + // See Knuth, ACP, Section 3.4.1 Algorithm C. + if (haveNextNextGaussian) { + haveNextNextGaussian = false; + return nextNextGaussian; + } else { + double v1, v2, s; + do { + v1 = 2 * nextDouble() - 1; // between -1 and 1 + v2 = 2 * nextDouble() - 1; // between -1 and 1 + s = v1 * v1 + v2 * v2; + } while (s >= 1 || s == 0); + double multiplier = StrictMath.sqrt(-2 * StrictMath.log(s) / s); + nextNextGaussian = v2 * multiplier; + haveNextNextGaussian = true; + return v1 * multiplier; + } + } + + /** + * Returns a pseudorandom, uniformly distributed {@code int} value between 0 (inclusive) and the specified value + * (exclusive), drawn from this random number generator's sequence. The general contract of {@code nextInt} is that + * one {@code int} value in the specified range is pseudorandomly generated and returned. All {@code bound} possible + * {@code int} values are produced with (approximately) equal probability. The method {@code nextInt(int bound)} is + * implemented by class {@code Random} as if by: + * + * <pre> + * {@code + * public int nextInt(int bound) { + * if (bound <= 0) + * throw new IllegalArgumentException("bound must be positive"); + * + * if ((bound & -bound) == bound) // i.e., bound is a power of 2 + * return (int)((bound * (long)next(31)) >> 31); + * + * int bits, val; + * do { + * bits = next(31); + * val = bits % bound; + * } while (bits - val + (bound-1) < 0); + * return val; + * }} + * </pre> + * + * <p> + * The next method is only approximately an unbiased source of independently chosen bits. If it were a perfect + * source of randomly chosen bits, then the algorithm shown would choose {@code int} values from the stated range + * with perfect uniformity. + * <p> + * The algorithm is slightly tricky. It rejects values that would result in an uneven distribution (due to the fact + * that 2^31 is not divisible by n). The probability of a value being rejected depends on n. The worst case is + * n=2^30+1, for which the probability of a reject is 1/2, and the expected number of iterations before the loop + * terminates is 2. + * <p> + * The algorithm treats the case where n is a power of two specially: it returns the correct number of high-order + * bits from the underlying pseudo-random number generator. In the absence of special treatment, the correct number + * of <i>low-order</i> bits would be returned. Linear congruential pseudo-random number generators such as the one + * implemented by this class are known to have short periods in the sequence of values of their low-order bits. + * Thus, this special case greatly increases the length of the sequence of values returned by successive calls to + * this method if n is a small power of two. + * + * @param bound the upper bound (exclusive). Must be positive. + * @return the next pseudorandom, uniformly distributed {@code int} value between zero (inclusive) and {@code bound} + * (exclusive) from this random number generator's sequence + * @throws IllegalArgumentException if bound is not positive + * @since 1.2 + */ + @Override + public int nextInt(int bound) { + last = seed ^ (seed << 21); + last ^= (last >>> 35); + last ^= (last << 4); + seed = last; + int out = (int) last % bound; + return (out < 0) ? -out : out; + } + + @Override + public int nextInt() { + return next(32); + } + + @Override + public float nextFloat() { + return next(24) * FLOAT_UNIT; + } + + @Override + public long nextLong() { + // it's okay that the bottom word remains signed. + return ((long) (next(32)) << 32) + next(32); + } + + @Override + public void nextBytes(byte[] bytes_arr) { + for (int iba = 0, lenba = bytes_arr.length; iba < lenba;) + for (int rndba = nextInt(), nba = Math.min(lenba - iba, Integer.SIZE / Byte.SIZE); nba-- + > 0; rndba >>= Byte.SIZE) bytes_arr[iba++] = (byte) rndba; + } +} |