// README FILE
// Pohlig-Hellman pseudorandom number generator with pseudorandom skip
// 32-bit implementation
// The period of each generator is P > 2^62 = 4.6e18
// The generator seeds itself on the first call using time in microseconds since 1/1/1970
//    and the processid and number of processes in MPI implementation
//  Each process is assigned an independent safe prime modulus in [2^31 .. 2^32]  
//     a safe prime n is a prime such that (n-1)/2 is also prime 
//
// Files randomph.cpp and randomph.h should be included 
//       and main.c or main.cpp must reference #include "randomph.h"


//32-bit Pohlig-Hellman pseudorandom number generator with pseudorandom skip.
// Returns double uniformly distributed on (0..1)
double randomph(void);



// returns state of generator
//    integerparameters[0]=m;
//    integerparameters[1]=s;
//    integerparameters[2]=c;
//    integerparameters[3]=n;
//    integerparameters[4]=e;
//    integerparameters[5]=p;
//    integerparameters[6]=a;
void getparameters_randomph(unsigned long * integerparameters);

//initialize generator, done automatically on the first call to randomph
void init_randomph(void);

//reinitialize generator with parameters m,s,n. 
//      e,p,a  are not changeable in this implementation
//    m=integerparameters[0];
//    s=integerparameters[1];
//    c=integerparameters[2];
//    n=integerparameters[3];
    //e=integerparameters[4]; 
    //p=integerparameters[5];
    //a=integerparameters[6];
void init_randomph(unsigned long * integerparameters);

// returns x^ e mod n for x,e,n < 2^32
unsigned long powermod(unsigned long x, unsigned long e, unsigned long n);

// Rabin-Miller primality test for n<2^32
// TRUE = 1 , FALSE = 0
int primeq(unsigned long n);



// tests to see if n is a safe prime for n<2^32
// TRUE = 1 , FALSE = 0
int safeprimeq(unsigned long n);


// selects the next prime above n if offset = +1, 
//       jth prime above n if offset = +j
// selects the next prime below n if offset = -1, 
//       jth prime below n if offset = -j
unsigned long nextprime(unsigned long n, long offset);


// selects the next safe prime above n if offset = +1, 
//       jth safe prime above n if offset = +j
// selects the next safe prime below n if offset = -1, 
//      jth safe prime below n if offset = -j
unsigned long nextsafeprime(unsigned long n, long offset);


//returns one of 3060794 safe primes between 2^31 and 2^32 starting near 2^32
// with 0 <= i < 3060794
// safeprime(0) = 4294967087  is the largest safe prime below 2^32
// safeprime(3060793) = 2147483783  is the smallest safe prime above 2^31
unsigned long safeprime(long i);