private ulong EvaluateInternal(ulong n, ulong x0, ulong xmax)
{
this.n = n;
x0 = T1(x0 + 1);
xmax = T1(xmax);
if (x0 > xmax)
{
return(0);
}
var ymin = YFloor(xmax);
var xmin = Math.Max(x0, Math.Min(T1(C1 * IntegerMath.CeilingRoot(2 * n, 3)), xmax));
#if DIAG
Console.WriteLine("n = {0}, xmin = {1}, xmax = {2}", n, xmin, xmax);
#endif
var s = (ulong)0;
var a2 = (ulong)1;
var x2 = xmax;
var y2 = ymin;
var c2 = a2 * x2 + y2;
while (true)
{
var a1 = a2 + 1;
var x4 = YTan(a1);
var y4 = YFloor(x4);
var c4 = a1 * x4 + y4;
var x5 = x4 + 1;
var y5 = YFloor(x5);
var c5 = a1 * x5 + y5;
if (x4 <= xmin)
{
break;
}
s += Triangle(c4 - c2 - x0) - Triangle(c4 - c2 - x5) + Triangle(c5 - c2 - x5);
if (threads == 0)
{
s += ProcessRegion(0, (ulong)(a1 * x2 + y2 - c5), (ulong)(a2 * x5 + y5 - c2), a1, 1, c5, a2, 1, c2);
while (stack.Count > 0)
{
var r = stack.Pop();
s += ProcessRegion(0, r.w, r.h, r.a1, r.b1, r.c1, r.a2, r.b2, r.c2);
}
}
else
{
Enqueue(new Region((ulong)(a1 * x2 + y2 - c5), (ulong)(a2 * x5 + y5 - c2), a1, 1, c5, a2, 1, c2));
}
a2 = a1;
x2 = x4;
y2 = y4;
c2 = c4;
}
s += (xmax - x0 + 1) * ymin + Triangle(xmax - x0);
var rest = x2 - x0;
s -= y2 * rest + a2 * Triangle(rest);
xmanual = x2;
return(s);
}