diff options
| -rw-r--r-- | src/dotnet-library/scala/util/Random.scala | 25 |
1 files changed, 14 insertions, 11 deletions
diff --git a/src/dotnet-library/scala/util/Random.scala b/src/dotnet-library/scala/util/Random.scala index 726f35478f..abfc654ce2 100644 --- a/src/dotnet-library/scala/util/Random.scala +++ b/src/dotnet-library/scala/util/Random.scala @@ -50,29 +50,32 @@ class Random(self0: System.Random) { /** Returns the next pseudorandom, Gaussian ("normally") distributed * double value with mean 0.0 and standard deviation 1.0 from this * random number generator's sequence. + * This implements the Box-Muller transformation on the pseudorandom + * `nextDouble` method of this class, and should be equivalent to + * the implementation of `nextGaussian` in the Java API. */ def nextGaussian(): Double = synchronized { if (nextGaussianAvailable) { nextGaussianAvailable = false - nextGaussian + nextGaussianCache } else { - var gauss1: Double - var gauss2: Double - var s: Double + var u: Double = 0.0 + var v: Double = 0.0 + var s: Double = 0.0 do { - gauss1 = 2 * nextDouble() - 1 // between -1.0 and 1.0 - gauss2 = 2 * nextDouble() - 1 // between -1.0 and 1.0 - s = Math.pow(gauss1) + Math.pow(gauss2) + u = 2 * nextDouble() - 1 // [-1, +1] + v = 2 * nextDouble() - 1 // [-1, +1] + s = Math.pow(u, 2) + Math.pow(v, 2) } while (s >= 1 || s == 0); - val multiplier = Math.sqrt(-2 * Math.log(s)/s) - nextGaussian = gauss1 * multiplier + val mul = Math.sqrt((-2 * Math.log(s)) / s) + nextGaussianCache = u * mul nextGaussianAvailable = true - gauss2 * multiplier + v * mul } } private var nextGaussianAvailable: Boolean = false - private var nextGaussian: Double = _ + private var nextGaussianCache: Double = _ /** Returns the next pseudorandom, uniformly distributed int value * from this random number generator's sequence. |