108 lines
2.5 KiB
C
108 lines
2.5 KiB
C
/*=============================================================================
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This file is part of FLINT.
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FLINT is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2 of the License, or
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(at your option) any later version.
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FLINT is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with FLINT; if not, write to the Free Software
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Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
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=============================================================================*/
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/******************************************************************************
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Copyright (C) 2012 Fredrik Johansson
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******************************************************************************/
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#include <stdio.h>
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#include <stdlib.h>
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#include "flint.h"
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#include "ulong_extras.h"
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static void
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mark(char * sieve, mp_limb_t a, slong len, mp_limb_t p)
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{
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mp_limb_t t;
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t = p * p;
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if (t >= a)
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{
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t = (t - a) / 2;
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}
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else
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{
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t = p - ((a - p) / 2) % p;
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if (t == p)
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t = 0;
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}
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while (t < len)
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{
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sieve[t] = 0;
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t += p;
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}
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}
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void
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n_sieve_odd(char * sieve, ulong n, mp_limb_t a,
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unsigned int * sieve_primes, mp_limb_t bound)
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{
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slong i;
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mp_limb_t p;
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for (i = 0; i < n / 2; i++)
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sieve[i] = 1;
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i = 0;
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while (1)
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{
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i++;
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p = sieve_primes[i];
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if (p > bound)
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break;
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mark(sieve, a, n / 2, p);
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}
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}
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void
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n_primes_sieve_range(n_primes_t iter, mp_limb_t a, mp_limb_t b)
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{
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mp_limb_t bound;
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ulong len, odd_len;
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/* a and b must be odd */
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a += (a % 2 == 0);
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b -= (b % 2 == 0);
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len = b - a + 2;
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odd_len = len / 2;
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if (a < 3 || b < a || len > FLINT_SIEVE_SIZE)
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{
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flint_printf("invalid sieve range %wu,%wu!\n", a, b);
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abort();
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}
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bound = n_sqrt(b) + 1;
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if (iter->sieve == NULL)
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iter->sieve = flint_malloc(FLINT_SIEVE_SIZE / 2 * sizeof(char));
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n_primes_extend_small(iter, bound);
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n_sieve_odd(iter->sieve, len, a, iter->small_primes, bound);
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iter->sieve_i = 0;
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iter->sieve_num = odd_len;
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iter->sieve_a = a;
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iter->sieve_b = b;
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}
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