private static T PopFromHeap(IReadOnlyList <T> choices, ref double[] weights, ref double[] totalWeights, IRandomProvider random)
{
var gas = random.NextDouble() * totalWeights[1];
var i = 1;
while (gas >= weights[i])
{
gas -= weights[i];
i <<= 1;
if (gas >= totalWeights[i])
{
gas -= totalWeights[i];
i += 1;
}
}
var weight = weights[i];
var chosen = choices[i];
weights[i] = 0;
while (i > 0)
{
totalWeights[i] -= weight;
i >>= 1;
}
return(chosen);
}
public static T PickSingleItem(List <WeightedChoice <T> > weights, IRandomProvider randomProvider)
{
var totalWeight = WeightsAddUpToOne(weights);
if (Math.Abs(1d - totalWeight) > Sensitivity)
{
throw new ArgumentException($"The weights for the items to choose do not add up to one. Total weight = {totalWeight}");
}
var randomValue = randomProvider.NextDouble();
for (var i = 0; i < weights.Count; i++)
{
var currentWeight = weights[i];
if (i == weights.Count - 1)
{
return(currentWeight.Choice); // last item on the list so it must be chosen
}
randomValue -= currentWeight.Weight;
if (randomValue < 0)
{
return(currentWeight.Choice);
}
}
throw new Exception("Failed to make a random choice");
}
public static IEnumerable <T> Shuffle <T>(this IEnumerable <T> enumerable, IRandomProvider randomProvider)
{
if (enumerable is null)
{
throw new ArgumentException("Enumerable is null.", "enumerable");
}
if (randomProvider is null)
{
throw new ArgumentException("Random Provider is null", "randomProvider");
}
return(enumerable.OrderBy(x => randomProvider.NextDouble()).ToList());
}
public static int Choice(int[] a, float[] p, IRandomProvider rng)
{
var roll = rng.NextDouble();
var cum = 0.0;
for (var i = 0; i < a.Length; i++)
{
cum += p[i];
if (roll < cum)
{
return(a[i]);
}
}
return(0);
}
public Question GetNextQuestion()
{
RefillAddoptions();
Question question = null;
if (randomProvider.NextDouble() > 0.3)
{
question = GetAdoptedQuestion();
}
if (question is null)
{
question = GetFreshQuestion();
}
if (question is null)
{
question = GetRrandomQuestion();
}
return(question);
}
public static List <int> ReservoirSampling(IEnumerable <double> weightStream, int k, IRandomProvider random)
{
var wSum = 0d;
var r = new List <int>(k);
if (k == 0)
{
return(r);
}
using var enumerator = weightStream.GetEnumerator();
for (var x = 0; x < k; x++)
{
enumerator.MoveNext();
var currentWeight = enumerator.Current;
r.Add(x);
wSum += currentWeight;
}
var i = k;
while (enumerator.MoveNext())
{
wSum += enumerator.Current;
var p = enumerator.Current / wSum;
var j = random.NextDouble();
if (j <= p)
{
var index = random.NextInt(0, k);
r[index] = i;
}
i++;
}
return(r);
}
void bar()
{
ans = r.NextDouble();
