样品code在C#中的快速素性测试 [英] Sample code for fast primality testing in C#
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问题描述
可能重复:
最快的算法素性测试
请问AP preciate一个参考样本code在C#快速素性测试,pferably使用的BigInteger或其他变量的大小类型。$ P $
Would appreciate a reference to sample code for fast primality testing in C#, preferably using BigInteger or other variable size type.
推荐答案
这是一个 米勒拉宾
测试在C#:</ P>
This is a Miller Rabin
test in c#:
bool MillerRabin(ulong n)
{
ulong[] ar;
if (n < 4759123141) ar = new ulong[] { 2, 7, 61 };
else if (n < 341550071728321) ar = new ulong[] { 2, 3, 5, 7, 11, 13, 17 };
else ar = new ulong[] { 2, 3, 5, 7, 11, 13, 17, 19, 23 };
ulong d = n - 1;
int s = 0;
while ((d & 1) == 0) { d >>= 1; s++; }
int i, j;
for (i = 0; i < ar.Length; i++)
{
ulong a = Math.Min(n - 2, ar[i]);
ulong now = pow(a, d, n);
if (now == 1) continue;
if (now == n - 1) continue;
for (j = 1; j < s; j++)
{
now = mul(now, now, n);
if (now == n - 1) break;
}
if (j == s) return false;
}
return true;
}
ulong mul(ulong a, ulong b, ulong mod)
{
int i;
ulong now = 0;
for (i = 63; i >= 0; i--) if (((a >> i) & 1) == 1) break;
for (; i >= 0; i--)
{
now <<= 1;
while (now > mod) now -= mod;
if (((a >> i) & 1) == 1) now += b;
while (now > mod) now -= mod;
}
return now;
}
ulong pow(ulong a, ulong p, ulong mod)
{
if (p == 0) return 1;
if (p % 2 == 0) return pow(mul(a, a, mod), p / 2, mod);
return mul(pow(a, p - 1, mod), a, mod);
}
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