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/* Dynamic Eratosthenes sieve.
Copyright 2001-2016 Paul Zimmermann and Alexander Kruppa.
Imported from CADO-NFS, which imported it from GMP-ECM.
(use 'unsigned long' instead of 'double'; thread-safe)
This file is part of the ECM Library.
The ECM Library is free software; you can redistribute it and/or modify
it under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation; either version 2.1 of the License, or (at your
option) any later version.
The ECM Library is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
License for more details.
You should have received a copy of the GNU Lesser General Public License
along with the ECM Library; see the file COPYING.LIB. If not, write to
the Free Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston,
MA 02110-1301, USA.
*/
/* compile with -DMAIN to use as a standalone program */
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "getprime_r.h"
/* provided for in cado.h, but we want getprime.c to be standalone */
#ifndef ASSERT
#define ASSERT(x)
#endif
/* This function returns successive odd primes, starting with 3.
To perform a loop over all primes <= B1, do the following
(compile this file with -DMAIN to count primes):
prime_info_t pi;
prime_info_init (pi);
for (p = 2; p <= B1; p = getprime_mt (pi))
{
...
}
prime_info_clear (pi);
*/
void
prime_info_init (prime_info_t i)
{
i->offset = 0;
i->current = -1;
i->primes = NULL;
i->nprimes = 0;
i->sieve = NULL;
i->len = 0;
i->moduli = NULL;
}
void
prime_info_clear (prime_info_t i)
{
free (i->primes);
free (i->sieve);
free (i->moduli);
}
/* this function is thread-safe */
ecm_uint
getprime_mt (prime_info_t i)
{
if (i->len)
{
unsigned char *ptr = i->sieve + i->current;
while (!*++ptr);
i->current = ptr - i->sieve;
}
else
i->current = 0;
if (i->current < i->len) /* most calls will end here */
return i->offset + 2 * i->current;
/* otherwise we have to sieve */
i->offset += 2 * i->len;
/* first enlarge sieving table if too small */
if ((ecm_uint) i->len * i->len < i->offset)
{
free (i->sieve);
i->len *= 2;
i->sieve = (unsigned char *) malloc ((i->len + 1 )
* sizeof (unsigned char));
/* assume this "small" malloc will not fail in normal usage */
ASSERT(i->sieve != NULL);
i->sieve[i->len] = 1; /* End mark */
}
/* now enlarge small prime table if too small */
if ((i->nprimes == 0) ||
((ecm_uint) i->primes[i->nprimes - 1] * (ecm_uint)
i->primes[i->nprimes - 1] < i->offset + i->len))
{
if (i->nprimes == 0) /* initialization */
{
i->nprimes = 1;
i->primes = (ecm_uint*) malloc (i->nprimes
* sizeof(ecm_uint));
/* assume this "small" malloc will not fail in normal usage */
ASSERT(i->primes != NULL);
i->moduli = (ecm_uint*) malloc (i->nprimes
* sizeof(ecm_uint));
/* assume this "small" malloc will not fail in normal usage */
ASSERT(i->moduli != NULL);
i->len = 1;
i->sieve = (unsigned char *) malloc((i->len + 1) *
sizeof(unsigned char)); /* len=1 here */
/* assume this "small" malloc will not fail in normal usage */
ASSERT(i->sieve != NULL);
i->sieve[i->len] = 1; /* End mark */
i->offset = 5;
i->sieve[0] = 1; /* corresponding to 5 */
i->primes[0] = 3;
i->moduli[0] = 1; /* next odd multiple of 3 is 7, i.e. next to 5 */
i->current = -1;
return 3;
}
else
{
ecm_uint k, p, j, ok;
k = i->nprimes;
i->nprimes *= 2;
i->primes = (ecm_uint*) realloc (i->primes, i->nprimes *
sizeof(ecm_uint));
i->moduli = (ecm_uint*) realloc (i->moduli, i->nprimes *
sizeof(ecm_uint));
/* assume those "small" realloc's will not fail in normal usage */
ASSERT(i->primes != NULL && i->moduli != NULL);
for (p = i->primes[k-1]; k < i->nprimes; k++)
{
/* find next (odd) prime > p */
do
{
for (p += 2, ok = 1, j = 0; (ok != 0) && (j < k); j++)
ok = p % i->primes[j];
}
while (ok == 0);
i->primes[k] = p;
/* moduli[k] is the smallest m such that
offset + 2*m = 0 mod p, i.e., moduli[k] = -offset/2 mod p */
j = i->offset % p;
j = (j == 0) ? j : p - j; /* -offset mod p */
if ((j % 2) != 0)
j += p; /* ensure j is even */
i->moduli[k] = j / 2;
}
}
}
/* now sieve for new primes */
{
ecm_int k;
ecm_uint j, p;
memset (i->sieve, 1, sizeof(unsigned char) * (i->len + 1));
for (j = 0; j < i->nprimes; j++)
{
p = i->primes[j];
for (k = i->moduli[j]; k < i->len; k += p)
i->sieve[k] = 0;
i->moduli[j] = k - i->len; /* for next sieving array */
}
}
{
unsigned char *ptr = i->sieve - 1;
while (!*++ptr);
i->current = ptr - i->sieve;
}
ASSERT(i->current < i->len); /* otherwise we found a prime gap >= sqrt(x)
around x */
return i->offset + 2 * i->current;
}
#ifdef MAIN
int
main (int argc, char *argv[])
{
unsigned long p, B;
unsigned long pi = 0;
prime_info_t i;
if (argc != 2)
{
fprintf (stderr, "Usage: getprime <bound>\n");
exit (EXIT_FAILURE);
}
B = strtoul (argv[1], NULL, 0);
prime_info_init (i);
for (pi = 0, p = 2; p <= B; p = getprime_mt (i), pi++);
printf ("pi(%lu)=%lu\n", B, pi);
prime_info_clear (i); /* free the tables */
return 0;
}
#endif
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