RateLimiter rateLimiter = new SmoothWarmingUp(stopwatch, warmupPeriod, unit, coldFactor);
    rateLimiter.setRate(permitsPerSecond);
    return rateLimiter;
  }

  /**
   * The underlying timer; used both to measure elapsed time and sleep as necessary. A separate
   * object to facilitate testing.
   */
  private final SleepingStopwatch stopwatch;

   * underlying model is a continuous function mapping storedPermits (from 0.0 to maxStoredPermits)
   * onto the 1/rate (i.e. intervals) that is effective at the given storedPermits. "storedPermits"
   * essentially measure unused time; we spend unused time buying/storing permits. Rate is
   * "permits / time", thus "1 / rate = time / permits". Thus, "1/rate" (time / permits) times

   * underlying model is a continuous function mapping storedPermits (from 0.0 to maxStoredPermits)
   * onto the 1/rate (i.e. intervals) that is effective at the given storedPermits. "storedPermits"
   * essentially measure unused time; we spend unused time buying/storing permits. Rate is
   * "permits / time", thus "1 / rate = time / permits". Thus, "1/rate" (time / permits) times

          if ((hash1 & (1 << k)) == (hash2 & (1 << k))) {
            same[k] += 1;
          } else {
            diff[k] += 1;
          }
        }
      }
      // measure probability and assert it's within margin of error
      for (int j = 0; j < hashBits; j++) {
        double prob = (double) diff[j] / (double) (diff[j] + same[j]);
        Assert.assertEquals(0.50d, prob, epsilon);
      }

    RateLimiter rateLimiter = new SmoothWarmingUp(stopwatch, warmupPeriod, unit, coldFactor);
    rateLimiter.setRate(permitsPerSecond);
    return rateLimiter;
  }

  /**
   * The underlying timer; used both to measure elapsed time and sleep as necessary. A separate
   * object to facilitate testing.
   */
  private final SleepingStopwatch stopwatch;