Viewing file:  920501-2.c (1.71 KB) -rw-r--r--
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unsigned long
gcd_ll (unsigned long long x, unsigned long long y)
{
for (;;)
{
if (y == 0)
return (unsigned long) x;
x = x % y;
if (x == 0)
return (unsigned long) y;
y = y % x;
}
}
unsigned long long
powmod_ll (unsigned long long b, unsigned e, unsigned long long m)
{
unsigned t;
unsigned long long pow;
int i;
if (e == 0)
return 1;
/* Find the most significant bit in E. */
t = e;
for (i = 0; t != 0; i++)
t >>= 1;
/* The most sign bit in E is handled outside of the loop, by beginning
with B in POW, and decrementing I. */
pow = b;
i -= 2;
for (; i >= 0; i--)
{
pow = pow * pow % m;
if ((1 << i) & e)
pow = pow * b % m;
}
return pow;
}
unsigned long factab[10];
void
facts (t, a_int, x0, p)
unsigned long long t;
int a_int;
int x0;
unsigned p;
{
unsigned long *xp = factab;
unsigned long long x, y;
unsigned long q = 1;
unsigned long long a = a_int;
int i;
unsigned long d;
int j = 1;
unsigned long tmp;
int jj = 0;
x = x0;
y = x0;
for (i = 1; i < 10000; i++)
{
x = powmod_ll (x, p, t) + a;
y = powmod_ll (y, p, t) + a;
y = powmod_ll (y, p, t) + a;
if (x > y)
tmp = x - y;
else
tmp = y - x;
q = (unsigned long long) q * tmp % t;
if (i == j)
{
jj += 1;
j += jj;
d = gcd_ll (q, t);
if (d != 1)
{
*xp++ = d;
t /= d;
if (t == 1)
{
return;
*xp = 0;
}
}
}
}
}
main ()
{
unsigned long long t;
unsigned x0, a;
unsigned p;
p = 27;
t = (1ULL << p) - 1;
a = -1;
x0 = 3;
facts (t, a, x0, p);
if (factab[0] != 7 || factab[1] != 73 || factab[2] != 262657)
abort();
exit (0);
}
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