code: // from gee.cs.oswego.edu/home/jsr166/jsr166
  
  package jsr166tests.loops;
  
  /*
   * Written by Doug Lea with assistance from members of JCP JSR-166
   * Expert Group and released to the public domain, as explained at
   * http://creativecommons.org/licenses/publicdomain
   */
  /**
   * Misc utilities in JSR166 performance tests
   */
  
  import java.util.concurrent.*;
  import java.util.concurrent.atomic.*;
  
  class LoopHelpers {
  
      static final SimpleRandom staticRNG = new SimpleRandom();
  
      // Some mindless computation to do between synchronizations...
  
      /**
       * generates 32 bit pseudo-random numbers.
       * Adapted from http://www.snippets.org
       */
      public static int compute1(int x) {
          int lo = 16807 * (x & 0xFFFF);
          int hi = 16807 * (x >>> 16);
          lo += (hi & 0x7FFF) << 16;
          if ((lo & 0x80000000) != 0) {
              lo &= 0x7fffffff;
              ++lo;
          }
          lo += hi >>> 15;
          if (lo == 0 || (lo & 0x80000000) != 0) {
              lo &= 0x7fffffff;
              ++lo;
          }
          return lo;
      }
  
      /**
       *  Computes a linear congruential random number a random number
       *  of times.
       */
      public static int compute2(int x) {
          int loops = (x >>> 4) & 7;
          while (loops-- > 0) {
              x = (x * 2147483647) % 16807;
          }
          return x;
      }
  
      /**
       * Yet another random number generator
       */
      public static int compute3(int x) {
          int t = (x % 127773) * 16807 - (x / 127773) * 2836;
          return (t > 0) ? t : t + 0x7fffffff;
      }
  
      /**
       * Yet another random number generator
       */
      public static int compute4(int x) {
          return x * 134775813 + 1;
      }
  
  
      /**
       * Yet another random number generator
       */
      public static int compute5(int x) {
          return 36969 * (x & 65535) + (x >> 16);
      }
  
      /**
       * Marsaglia xorshift (1, 3, 10)
       */
      public static int compute6(int seed) {
          seed ^= seed << 1;
          seed ^= seed >>> 3;
          seed ^= (seed << 10);
          return seed;
      }
  
      /**
       * Marsaglia xorshift (6, 21, 7)
       */
      public static int compute7(int y) {
          y ^= y << 6;
          y ^= y >>> 21;
          y ^= (y << 7);
          return y;
      }
  
      // FNV: (x ^ 0x811c9dc5) * 0x01000193;  15485863;
  
      /**
       * Marsaglia xorshift for longs
       */
      public static long compute8(long x) {
          x ^= x << 13;
          x ^= x >>> 7;
          x ^= (x << 17);
          return x;
      }
  
      public static final class XorShift32Random {
          static final AtomicInteger seq = new AtomicInteger(8862213);
          int x = -1831433054;
          public XorShift32Random(int seed) { x = seed;  }
          public XorShift32Random() {
              this((int) System.nanoTime() + seq.getAndAdd(129));
          }
          public int next() {
              x ^= x << 6;
              x ^= x >>> 21;
              x ^= (x << 7);
              return x;
          }
      }
  
  
      /** Multiplication-free RNG from Marsaglia "Xorshift RNGs" paper */
      public static final class MarsagliaRandom {
          static final AtomicInteger seq = new AtomicInteger(3122688);
          int x;
          int y = 842502087;
          int z = -715159705;
          int w = 273326509;
          public MarsagliaRandom(int seed) { x = seed; }
          public MarsagliaRandom() {
              this((int) System.nanoTime() + seq.getAndAdd(129));
          }
          public int next() {
              int t = x ^ (x << 11);
              x = y;
              y = z;
              z = w;
              return w = (w ^ (w >>> 19) ^ (t ^ (t >>> 8)));
          }
      }
  
      /**
       * Unsynchronized version of java.util.Random algorithm.
       */
      public static final class SimpleRandom {
          private final static long multiplier = 0x5DEECE66DL;
          private final static long addend = 0xBL;
          private final static long mask = (1L << 48) - 1;
          static final AtomicLong seq = new AtomicLong( -715159705);
          private long seed;
  
          SimpleRandom(long s) {
              seed = s;
          }
  
          SimpleRandom() {
              seed = System.nanoTime() + seq.getAndAdd(129);
          }
  
          public void setSeed(long s) {
              seed = s;
          }
  
          public int next() {
              long nextseed = (seed * multiplier + addend) & mask;
              seed = nextseed;
              return ((int) (nextseed >>> 17)) & 0x7FFFFFFF;
          }
      }
  
      public static class BarrierTimer implements Runnable {
          volatile boolean started;
          volatile long startTime;
          volatile long endTime;
          public void run() {
              long t = System.nanoTime();
              if (!started) {
                  started = true;
                  startTime = t;
              } else
                  endTime = t;
          }
          public void clear() {
              started = false;
          }
          public long getTime() {
              return endTime - startTime;
          }
      }
  
      public static String rightJustify(long n) {
          // There's probably a better way to do this...
          String field = "         ";
          String num = Long.toString(n);
          if (num.length() >= field.length())
              return num;
          StringBuffer b = new StringBuffer(field);
          b.replace(b.length()-num.length(), b.length(), num);
          return b.toString();
      }
  
  }
  