public void Add_PsrngZeroSum_ExpectBetterAccuracyThanNaive(SumKind kind)
{
const double Spread = 1E7;
var sum = CreateSum(kind);
var naive = CreateSum(SumKind.Naive);
var rand = new Random(2002);
for (int n = 0; n < 1000000; ++n)
{
double x = rand.NextDouble() * Spread;
sum.Add(x);
naive.Add(x);
}
rand = new Random(2002);
for (int n = 0; n < 1000000; ++n)
{
double x = rand.NextDouble() * Spread;
sum.Add(-x);
naive.Add(-x);
}
helper.WriteLine("RESULT: " + Math.Abs(sum.Value));
helper.WriteLine("NAIVE: " + Math.Abs(naive.Value));
// Since we also test Naive as we want output, test
// LTE instead of LT.
Assert.True(Math.Abs(sum.Value) <= Math.Abs(naive.Value));
}
public void Add_MeasurePerformance(SumKind kind)
{
const long TicksPerSecond = 1000 * 1000 * 10;
var sum = CreateSum(kind);
// JIT
sum.Add(1);
sum.Clear();
double elap;
long count = 0;
var sw = Stopwatch.StartNew();
do
{
for (int n = 0; n < 1000; ++n)
{
sum.Add(++count);
}
elap = (double)sw.ElapsedTicks / TicksPerSecond;
} while (elap < 1.0);
helper.WriteLine("Count: " + count);
helper.WriteLine("Elapsed: " + elap + " sec");
helper.WriteLine("RATE: " + count / elap + " per sec");
helper.WriteLine("TIME: " + 1E9 * elap / count + " ns");
}
public void Reset_PerformsFullReset(SumKind kind)
{
var sum = CreateSum(kind);
sum.Add(1.5);
sum.Clear();
Assert.Equal(0.0, sum.Value, 10);
// Restarts
sum.Add(1.5);
Assert.Equal(1.5, sum.Value, 10);
}
private static ICompensatedSum CreateSum(SumKind kind)
{
switch (kind)
{
case SumKind.Pairwise: return(new PairwiseSum());
case SumKind.Kahan: return(new KahanSum());
case SumKind.Neumaier: return(new NeumaierSum());
case SumKind.Klein: return(new KleinSum());
default: return(new NaiveSum());
}
}
public void Add_PetersTest_ExpectSumOf2(SumKind kind)
{
// https://en.wikipedia.org/wiki/Kahan_summation_algorithm
var sum = CreateSum(kind);
sum.Add(1.0);
sum.Add(1E100);
sum.Add(1.0);
sum.Add(-1E100);
// Only Neumaier and Klein both give correct answer 2.0.
// Others expected to give 0.
helper.WriteLine(sum.Value.ToString());
Assert.Equal(2.0, sum.Value, 10);
}
