/*
	This package requires the GNU MP package available at:
	http://www.swox.com/gmp/
	To compile the program run:
	gcc -lm -lgmp -o germain germain.c
*/

#include <stdio.h>
#include <gmp.h>
#include <math.h>

void mpz_nextgermain(mpz_t, mpz_t);
void mpz_nextinterval(mpz_t [], mpz_t []);

main(int argc, char *argv[])
{
	int	n, num, Pig;
	double	PigLog;		
	mpz_t	cogermain, germain, gertail, Interval[2];
	char	filename[10];
	FILE	*gprimes;

	num = 10;	  
	Pig = 0; PigLog = 0;

	mpz_init(germain);	mpz_init(cogermain);	mpz_init(gertail);

	mpz_init(Interval[0]);	mpz_init(Interval[1]);
	mpz_ui_pow_ui(Interval[0], 10, 18);
	mpz_ui_pow_ui(Interval[1], 10, 9);
	mpz_add(Interval[1], Interval[0], Interval[1]);

	for ( n = 0 ; n < num ; n++ ) {
		sprintf(filename, "%.2d.gprimes",
		 mpz_sizeinbase(Interval[0], 10) - 1);

		printf("Creating file %s.\n", filename);
		if ( (gprimes = fopen(filename, "a")) == NULL ) {
			fprintf(stderr, "can't open file\n");
			exit(1);
		}	
		
		mpz_nextgermain(germain, Interval[0]);

		while ( mpz_cmp(germain, Interval[1]) < 0 ) {
			mpz_sub(gertail, germain, Interval[0]);
			gmp_fprintf(gprimes, "%Zd\n", gertail);

			mpz_mul_ui(cogermain, germain, 2);
			mpz_add_ui(cogermain, cogermain, 1);

			Pig++;
			PigLog = PigLog + log( mpz_get_d(germain) )
			 * log( mpz_get_d(cogermain) );

			mpz_nextgermain(germain, germain);
		}

		gmp_fprintf(gprimes, "(%Zd,%Zd) %d %f\n",
		 Interval[0], Interval[1], Pig, PigLog);
		fclose(gprimes);

		Pig = 0;	PigLog = 0;
		mpz_nextinterval(Interval, Interval);
	}
}


void mpz_nextinterval(mpz_t Outpoint[2], mpz_t Inpoint[2]) {
	mpz_t	Left, Right;

	mpz_init_set(Left, Inpoint[0]);
	mpz_init_set(Right, Inpoint[1]);

	mpz_sub(Right, Right, Left);
	mpz_mul_ui(Left, Left, 10);
	mpz_add(Right, Right, Left);

	gmp_printf("Completed interval (%Zd,%Zd).\n", Left, Right);

	mpz_set(Outpoint[0], Left);
	mpz_set(Outpoint[1], Right);

	mpz_clear(Left);
	mpz_clear(Right);
	return;
}

void mpz_nextgermain(mpz_t Outpoint, mpz_t Inpoint) {
	mpz_t	Germain, CoGermain;

	mpz_init_set(Germain, Inpoint);
	mpz_init_set_ui(CoGermain, 4);

	while ( !mpz_probab_prime_p(CoGermain, 5) ) {
		mpz_nextprime(Germain, Germain);
		mpz_mul_ui(CoGermain, Germain, 2);
		mpz_add_ui(CoGermain, CoGermain, 1);
	}
		
	mpz_set(Outpoint, Germain);
	mpz_clear(Germain);
	mpz_clear(CoGermain);
	return;
}