public void SampleGeometric()
{
Rand.Restart(96);
const double StoppingProbability = 0.7;
// The length of sequences sampled from this distribution must follow a geometric distribution
StringAutomaton automaton = StringAutomaton.Zero();
automaton.Start = automaton.AddState();
automaton.Start.SetEndWeight(Weight.FromValue(StoppingProbability));
automaton.Start.AddTransition('a', Weight.FromValue(1 - StoppingProbability), automaton.Start);
StringDistribution dist = StringDistribution.FromWeightFunction(automaton);
var acc = new MeanVarianceAccumulator();
const int SampleCount = 30000;
for (int i = 0; i < SampleCount; ++i)
{
string sample = dist.Sample();
acc.Add(sample.Length);
}
const double ExpectedMean = (1.0 - StoppingProbability) / StoppingProbability;
const double ExpectedVariance = (1.0 - StoppingProbability) / (StoppingProbability * StoppingProbability);
Assert.Equal(ExpectedMean, acc.Mean, 1e-2);
Assert.Equal(ExpectedVariance, acc.Variance, 1e-2);
}