| static public Product ( long seq, int start, int len ) : Arithmetic.XInt | ||
| seq | long | |
| start | int | |
| len | int | |
| return | Arithmetic.XInt | |
public XInt GetPrimorial(uint min, uint max)
{
var mem = (int)(0.63 * max / System.Math.Log(max));
var plist = new long[mem];
var size = 0;
if (min <= 2)
{
plist[size++] = 2;
}
if (min <= 3)
{
plist[size++] = 3;
}
var absPos = (int)((min + (min + 1) % 2) / 3 - 1);
var index = absPos / BitsPerInt;
var bitPos = absPos % BitsPerInt;
bool toggle = (bitPos & 1) == 1;
var prime = (uint)(5 + 3 * (BitsPerInt * index + bitPos) - (bitPos & 1));
while (prime <= max)
{
var bitField = this.isComposite[index++] >> bitPos;
for (; bitPos < BitsPerInt; bitPos++)
{
if ((bitField & 1) == 0)
{
plist[size++] = prime;
}
prime += (toggle = !toggle) ? 2u : 4u;
if (prime > max)
{
return(MathFun.Product(plist, 0, size));
}
bitField >>= 1;
}
bitPos = 0;
}
return(XInt.Zero);
}
public XInt Product()
{
this.factors[this.count++] = this.prod;
return(MathFun.Product(this.factors, 0, this.count));
}