IEnumerable ISelectionStrategy.Select(ISelectableItemCollection items, int count)
{
Contract.Requires(items != null);
Contract.Requires(count > 0);
Contract.Ensures(Contract.Result<IEnumerable>() != null);
return null;
}
public IEnumerable Select(ISelectableItemCollection orderedItems, int count)
{
var returned = new HashSet<int>();
int itemCount = orderedItems.Count;
while (returned.Count != count)
{
int index = RandomGenerator.Random.Next(itemCount);
if (!returned.Contains(index))
{
var item = orderedItems.Select(index);
yield return item;
returned.Add(index);
}
}
}
public System.Collections.IEnumerable Select(ISelectableItemCollection orderedItems, int count)
{
int itemCount = orderedItems.Count;
int tournamentSize = TournamentSize;
if (tournamentSize < count) tournamentSize = count;
if (tournamentSize > itemCount) tournamentSize = itemCount;
var arena = new SortedDictionary<int, object>();
while (arena.Count != tournamentSize)
{
int index = RandomGenerator.Random.Next(itemCount);
if (!arena.ContainsKey(index)) arena.Add(index, orderedItems.Select(index));
}
var baseProbability = BestWinChance;
var p = baseProbability;
int returnedCount = 0;
while (returnedCount != count)
{
int index = 0;
int winnerIndex = -1;
object winner = null;
foreach (var kvp in arena)
{
if (p)
{
winnerIndex = kvp.Key;
winner = kvp.Value;
break;
}
p = (double)baseProbability * Math.Pow((1.0 - (double)baseProbability), index++);
}
if (winnerIndex != -1)
{
yield return winner;
arena.Remove(winnerIndex);
returnedCount++;
}
}
}
