67 lines
2.2 KiB
C
67 lines
2.2 KiB
C
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/*=============================================================================
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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) 2010 Fredrik Johansson
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******************************************************************************/
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#include <gmp.h>
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#include "flint.h"
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#include "ulong_extras.h"
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const unsigned char FLINT_PRIME_PI_ODD_LOOKUP[] =
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{
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0,2,3,4,4,5,6,6,7,8,8,9,9,9,10,11,11,11,12,12,13,14,14,15,15,15,16,16,16,17,
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18,18,18,19,19,20,21,21,21,22,22,23,23,23,24,24,24,24,25,25,26,27,27,28,29,
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29,30,30,30,30,30,30,30,31,31,32,32,32,33,34,34,34,34,34,35,36,36,36,37,37,
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37,38,38,39,39,39,40,40,40,41,42,42,42,42,42,43,44,44,45,46,46,46,46,46,46,
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47,47,47,47,47,47,48,48,49,50,50,51,51,51,52,53,53,53,53,53,54,54,54,55,55,
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55,56,56,56,57,58,58,58,59,59,60,61,61,61,61,61,62,62,62,62,62,62,62,63,63
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};
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ulong n_prime_pi(mp_limb_t n)
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{
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ulong low, mid, high;
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const mp_limb_t * primes;
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if (n < FLINT_PRIME_PI_ODD_LOOKUP_CUTOFF)
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{
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if (n < 3)
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return (n == 2);
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return FLINT_PRIME_PI_ODD_LOOKUP[(n-1)/2];
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}
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n_prime_pi_bounds(&low, &high, n);
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primes = n_primes_arr_readonly(high + 1);
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while (low < high)
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{
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mid = (low + high) / 2;
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if (n < primes[mid-1])
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high = mid;
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else
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low = mid + 1;
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}
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return low-1;
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}
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