public static unsafe TResult SumRange <TResult, TVectorSelector, TSelector>(int start, int count, TVectorSelector vectorSelector, TSelector selector)
where TVectorSelector : struct, IFunction <Vector <int>, Vector <TResult> >
where TSelector : struct, IFunction <int, TResult>
where TResult : struct
{
var sum = default(TResult);
var index = 0;
if (Vector.IsHardwareAccelerated && count > Vector <TResult> .Count * 4) // use SIMD
{
var seed = stackalloc int[Vector <TResult> .Count];
if (start is 0)
{
for (index = 0; index < Vector <TResult> .Count; index++)
{
seed[index] = index;
}
}
else
{
for (index = 0; index < Vector <TResult> .Count; index++)
{
seed[index] = index + start;
}
}
var vector = Unsafe.AsRef <Vector <int> >(seed);
var vectorIncrement = new Vector <int>(Vector <TResult> .Count);
var vectorSum = Vector <TResult> .Zero;
for (index = 0; index <= count - Vector <TResult> .Count; index += Vector <TResult> .Count)
{
vectorSum += vectorSelector.Invoke(vector);
vector += vectorIncrement;
}
for (index = 0; index < Vector <TResult> .Count; index++)
{
sum = GenericsOperator.Add(vectorSum[index], sum);
}
}
if (start is 0)
{
for (; index < count; index++)
{
sum = GenericsOperator.Add(selector.Invoke(index), sum);
}
}
else
{
for (; index < count; index++)
{
sum = GenericsOperator.Add(selector.Invoke(index + start), sum);
}
}
return(sum);
}
static TResult Sum <TSource, TResult, TVectorSelector, TSelector>(this ReadOnlySpan <TSource> source, TVectorSelector vectorSelector, TSelector selector)
where TVectorSelector : struct, IFunction <Vector <TSource>, Vector <TResult> >
where TSelector : struct, IFunction <TSource, TResult>
where TSource : struct
where TResult : struct
{
var sum = default(TResult);
if (Vector.IsHardwareAccelerated && source.Length > Vector <TResult> .Count * 2) // use SIMD
{
var vectors = MemoryMarshal.Cast <TSource, Vector <TSource> >(source);
var vectorSum = Vector <TResult> .Zero;
foreach (var vector in vectors)
{
vectorSum += vectorSelector.Invoke(vector);
}
for (var index = 0; index < Vector <TResult> .Count; index++)
{
sum = GenericsOperator.Add(vectorSum[index], sum);
}
for (var index = source.Length - (source.Length % Vector <TSource> .Count); index < source.Length; index++)
{
var item = source[index];
sum = GenericsOperator.Add(selector.Invoke(item), sum);
}
}
else
{
foreach (var item in source)
{
sum = GenericsOperator.Add(selector.Invoke(item), sum);
}
}
return(sum);
}
///////////////////////////////////////////////////////////
static TSource Sum <TSource>(this ReadOnlySpan <TSource> source)
where TSource : struct
{
var sum = default(TSource);
if (Vector.IsHardwareAccelerated && source.Length > Vector <TSource> .Count * 2) // use SIMD
{
var vectors = MemoryMarshal.Cast <TSource, Vector <TSource> >(source);
var vectorSum = Vector <TSource> .Zero;
foreach (var vector in vectors)
{
vectorSum += vector;
}
for (var index = 0; index < Vector <TSource> .Count; index++)
{
sum = GenericsOperator.Add(vectorSum[index], sum);
}
for (var index = source.Length - (source.Length % Vector <TSource> .Count); index < source.Length; index++)
{
var item = source[index];
sum = GenericsOperator.Add(item, sum);
}
}
else
{
foreach (var item in source)
{
sum = GenericsOperator.Add(item, sum);
}
}
return(sum);
}