public static MultiPrecision <N> Erfc(MultiPrecision <N> x)
{
if (x.IsZero)
{
return(1);
}
if (x.IsNaN)
{
return(NaN);
}
if (!x.IsFinite)
{
return(x.Sign == Sign.Plus ? 0 : 2);
}
if (x.Sign == Sign.Minus)
{
return(1 + Erf(Abs(x)));
}
if (x.Exponent < Consts.Erf.ExponentThreshold)
{
MultiPrecision <Plus4 <Plus4 <N> > > y =
MultiPrecision <Plus4 <N> > .ErfTaylorSeriesApprox(x.Convert <Plus4 <N> >());
return((1 - y).Convert <N>());
}
else
{
long n = ErfcConvergenceTable.N(Bits, (double)x);
MultiPrecision <Plus4 <N> > y = ErfcContinueFractionalApprox(x, n);
return(y.Convert <N>());
}
}
public static MultiPrecision <N> Erf(MultiPrecision <N> x)
{
if (x.IsZero)
{
return(0);
}
if (x.IsNaN)
{
return(NaN);
}
if (!x.IsFinite)
{
return(x.Sign == Sign.Plus ? 1 : -1);
}
if (x.Sign == Sign.Minus)
{
return(-Erf(Abs(x)));
}
if (x.Exponent < Consts.Erf.ExponentThreshold)
{
MultiPrecision <Plus4 <N> > y = ErfTaylorSeriesApprox(x);
return(y.Convert <N>());
}
else
{
double xd = (double)x;
double erfc_exponent_estimate = 1.4 * xd * xd;
int needs_bits = Bits - (int)Math.Min(Bits, erfc_exponent_estimate);
if (needs_bits < 1)
{
return(1);
}
long n = ErfcConvergenceTable.N(needs_bits, xd);
MultiPrecision <Plus4 <N> > y = ErfcContinueFractionalApprox(x, n);
return((1 - y).Convert <N>());
}
}
