static void
calc_primes(char *bitmap, uint64_t max)
{
char *bmp,
*bitmap_end = bitmap + max / 30 + 1,
pattern[16 * 8];
uint64_t a;
int i,
j,
r,
a_i,
offsets[8];
/*** Main algorithm start ***/
for (i = 1; i < 4; i++) {
bzero(pattern, sizeof pattern);
for (r = bval[i], a_i = 0; r < bval[i] * 30 * 8; r += bval[i] * diff[a_i++ % 8])
pattern[r / 30] |= 1 << num2bit(r);
for (bmp = bitmap; bmp < bitmap_end; bmp += bval[i] * sizeof(uint64_t))
for (j = 0; j < bval[i]; j++)
*((uint64_t *)bmp + j) |= *((uint64_t *)pattern + j);
}
/*** Main algorithm end ***/
for (a = 17, a_i = 4; a <= sqrtl(max); a += diff[a_i++%8]) {
if (bitmap[a / 30] & 1 << (a_i%8))
continue;
for (i = 0; i < 8; i++)
offsets[num2bit(a * bval[i])] = a * bval[i] / 30;
for (bmp = bitmap + a * (a / 30); bmp < bitmap_end; bmp += a)
for (i = 0; i < 8; i++)
*(bmp + offsets[i]) |= 1 << i;
}
/* Fix first byte which is clobbered above */
bitmap[0] = 0x1;
}
int
main(int argc, char *argv[])
{
uint64_t max = argc > 1 ? atol(argv[1]) : 1000000000ull;
char *bitmap = calloc(max/30 + sqrtl(max) + 16*8, 1);
uint64_t adj_max;
int a_i;
/* adjust max to a multiple of 2,3,5 */
for (adj_max = (max - 1) / 30 * 30 + 1, a_i = 0;
adj_max + diff[a_i%8] <= max;
adj_max += diff[a_i++%8])
;
calc_primes(bitmap, adj_max);
printf("%ld\n", count_primes(bitmap, adj_max / 30 * 8 + num2bit(adj_max)) + 3);
free(bitmap);
return EXIT_SUCCESS;
}
static void
calc_primes(char *bitmap, uint64_t max)
{
char *bmp,
*bitmap_end = bitmap + 32*1024;
uint64_t a,
cur;
int i,
a_i,
offsets[8];
/*** Main algorithm start ***/
for (cur = 0; cur <= max; cur += 32*1024*30, bitmap_end += 32*1024) {
for (a = 7, a_i = 1; a <= sqrtl(cur + 32*1024*30); a += diff[a_i++%8]) {
if (bitmap[a / 30] & 1 << (a_i%8))
continue;
for (i = 0; i < 8; i++)
offsets[num2bit(a * bval[i])] = a * bval[i] / 30;
for (bmp = bitmap + MAX(a * (a / 30), (cur / 30) / a * a);
bmp < bitmap_end;
bmp += a) {
for (i = 0; i < 8; i++)
*(bmp + offsets[i]) |= 1 << i;
}
}
/* First byte gets clobbered for the first block */
if (cur == 0)
bitmap[0] = 0x1;
}
/*** Main algorithm end ***/
}
int uadd_ok(unsigned x, unsigned y)
{
return (((num2bit(x)+num2bit(y)) > 32) ? 0 : 1);
}