public int CompareTo(MeasuredItem <TItem, TMeasure> other)
{
if (other == null)
{
return(-1);
}
var cmp = Measure.CompareTo(other.Measure);
return(cmp != 0 ? cmp : _multiplier *Item.GetHashCode().CompareTo(other.Item.GetHashCode()));
}
public static IEnumerable <TMeasurable> TopN <TMeasurable, TMeasure>(this IEnumerable <TMeasurable> items,
TMeasurable reference, int k, SelectParallelOptions options = null)
where TMeasure : IComparable <TMeasure>
where TMeasurable : IMeasurable <TMeasurable, TMeasure>
{
if (options == null)
{
options = new SelectParallelOptions();
}
MeasuredItem <TMeasurable, TMeasure>[] measuredItems;
if (options.TaskCount == 1)
{
measuredItems =
items.Select(item => new MeasuredItem <TMeasurable, TMeasure>(item, reference.Measure(item), true))
.ToArray();
}
else
{
var itemsArray = items as TMeasurable[] ?? items.ToArray();
measuredItems = new MeasuredItem <TMeasurable, TMeasure> [itemsArray.Length];
// See http://www.codeproject.com/Articles/451628/Efficient-Map-Operations-for-Arrays-in-Csharp
// Parallel.ForEach with range partitioner may be faster than other ways for > 10000 items.
// It certainly was faster than using Task.Factory.StartNew and Task.WaitAll.
Parallel.ForEach(Partitioner.Create(0, itemsArray.Length),
range =>
{
for (int i = range.Item1; i < range.Item2; ++i)
{
var item = itemsArray[i];
// ReSharper disable once AccessToModifiedClosure
measuredItems[i] = new MeasuredItem <TMeasurable, TMeasure>(item, reference.Measure(item), true);
}
}
);
}
return(measuredItems
.TopNParallel(k, null, options)
.Select(measuredItem => measuredItem.Item)
.Reverse()
);
}