sieve.c

#include <stdio.h>
#include <malloc.h>
#include <time.h>

#define TEST(f,x)       (*(f+(x)/16)&(1<<(((x)%16L)/2)))
#define SET(f,x)        *(f+(x)/16)|=1<<(((x)%16L)/2)

int main(int argc, char *argv[]){
	unsigned char *feld = NULL, *zzz;
	unsigned long teste = 1, max, mom, hits = 1, count, alloc, s = 0, e = 1;
	time_t begin;
	if(argc > 1)
		max = atol(argv[1]) + 10000;
	else
		max = 14010000L;
	while(feld == NULL)
		zzz = feld = malloc(alloc = (((max -= 10000L) >> 4) + 1L));
	for(count = 0; count < alloc; count++)
		*zzz++ = 0x00;
	printf("Searching prime numbers to : %ld\n", max);
	begin = time(NULL);
	while((teste += 2) < max)
		if(!TEST(feld, teste)){
			if(++hits % 2000L == 0){
				printf(" %ld. prime number\x0d", hits);
				fflush(stdout);
			}
			for(mom = 3L * teste; mom < max; mom += teste <<1 )
				SET (feld, mom);
		}
	printf(" %ld prime numbers foundn %ld secs.\n\nShow prime numbers", hits, time(NULL)-begin);
	while(s < e){
		printf("\n\nStart of Area : ");
		fflush(stdout);
		scanf("%ld", &s);
		printf("End   of Area : ");
		fflush(stdout);
		scanf("%ld", &e);
		count = s - 2;
		if(s%2==0)
			count++;
		while((count += 2) < e)
			if(!TEST(feld, count))
				printf("%ld\t", count);
	}
	free(feld);
}