public BigInteger BigIntZeta(uint s) // must be +ve integer > 1
{
BigInteger unity = BigInteger.Pow(ONE, (int)(s >> 1)); // normalize to become 1 in the numerator
double sum = 1.0d;
BigInteger zeta = unity;
object monitor = new object();
Stopwatch sw = new Stopwatch();
WriteLine("Calculating BigIntZeta({2}) with {0} iterations and {1} digits.\n", STEPS, DIGITS, s);
sw.Start();
Parallel.For <Tuple <double, BigInteger> >(2, (int)STEPS, () => new Tuple <double, BigInteger>(2.0d, 2), (i, loop, T) =>
//for (uint i = 2; i < STEPS; i++)
{
BigInteger div = BigInteger.Pow(i, (int)s);
//zeta += unity / j;
sum += 1.0d / Math.Pow(i, s);
ValueTuple <double, BigInteger> X = T.ToValueTuple();
X.Item1 += i;
X.Item2 += unity / div;
return(X.ToTuple());
}, t =>
{
lock (monitor)
{
sum += t.Item1;
zeta += t.Item2;
}
});
sw.Stop();
#if DEBUG
string strElapsed;
if (sw.ElapsedMilliseconds <= 1000)
{
strElapsed = String.Format("{0} ms", sw.ElapsedMilliseconds);
}
else
{
strElapsed = String.Format("{0:F1} s", sw.Elapsed.TotalSeconds);
}
WriteLine($"\n\nBigIntZeta({s}):\n{zeta}\nElapsed time: {strElapsed}\n");
#endif
WriteLine();
return(zeta);
}
public static void Add <T1, T2>(this IList <Tuple <T1, T2> > list,
ValueTuple <T1, T2> item) => list.Add(item.ToTuple());