//计算 x^n %c
long long pow_mod(long long x,long long n,long long mod){
if(n==1)return x%mod;
x%=mod;
long long tmp=x;
long long ret=1;
while(n){
if(n&1) ret=mult_mod(ret,tmp,mod);
tmp=mult_mod(tmp,tmp,mod);
n>>=1;
}
return ret;
}
/*
* prng_meicg_get_next_int: Return next mEICG number (unscaled)
*
* Input:
* gen: Pointer to a struct prng.
*
*/
inline prng_num prng_meicg_get_next_int(struct prng *gen)
{
s_prng_num an, sum, inv, n;
n = gen->data.meicg_data.next_n;
an = mult_mod(n, & (gen->data.meicg_data.mm));
add_mod(sum,an,gen->data.meicg_data.b,gen->data.meicg_data.p);
if (++gen->data.meicg_data.next_n == gen->data.meicg_data.p )
gen->data.meicg_data.next_n = 0;
inv = prng_inverse(sum,gen->data.meicg_data.p);
if (gen->data.meicg_data.simple_square) /* can use straight f. ? */
{
return((n * inv ) % gen->data.meicg_data.p);
}
else
{
#ifdef HAVE_LONGLONG
return(mult_mod_ll(n,inv,gen->data.meicg_data.p));
#else
return(mult_mod_generic(n,inv,gen->data.meicg_data.p));
#endif
}
/* not reached */
}
//以a为基,n-1=x*2^t a^(n-1)=1(mod n) 验证n是不是合数
//一定是合数返回true,不一定返回false
bool check(long long a,long long n,long long x,long long t){
long long ret=pow_mod(a,x,n);
long long last=ret;
for(int i=1;i<=t;i++){
ret=mult_mod(ret,ret,n);
if(ret==1&&last!=1&&last!=n-1) return true;//合数
last=ret;
}
if(ret!=1) return true;
return false;
}
long long Pollard_rho(long long x,long long c){
long long i=1,k=2;
long long x0=rand()%x;
long long y=x0;
while(1){
i++;
x0=(mult_mod(x0,x0,x)+c)%x;
long long d=gcd(y-x0,x);
if(d!=1&&d!=x) return d;
if(y==x0) return x;
if(i==k){y=x0;k+=k;}
}
}
