57 lines
1.8 KiB
C
57 lines
1.8 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) 2009 Thomas Boothby
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Copyright (C) 2009 William Hart
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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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int n_is_oddprime_binary(mp_limb_t n)
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{
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ulong diff, prime_lo, prime_hi;
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const mp_limb_t * primes;
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n_prime_pi_bounds(&prime_lo, &prime_hi, n);
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primes = n_primes_arr_readonly(prime_hi + 1);
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if (n == primes[prime_hi]) return 1;
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if (n > primes[prime_hi]) return 0;
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diff = (prime_hi - prime_lo + 1) / 2;
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while (1)
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{
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ulong diff2;
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if (primes[prime_lo + diff] <= n) prime_lo += diff;
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if (diff <= UWORD(1)) break;
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diff = (diff + 1)/2;
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diff2 = (prime_hi - prime_lo + 1)/2;
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if (diff > diff2) diff = diff2;
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}
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return (n == primes[prime_lo]);
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}
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