68 lines
1.9 KiB
C
68 lines
1.9 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 William Hart
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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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mp_limb_t
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n_mod2_precomp(mp_limb_t a, mp_limb_t n, double npre)
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{
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mp_limb_t quot;
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slong rem;
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if (a < n)
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return a;
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if ((mp_limb_signed_t) n < WORD(0))
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return a - n;
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if (n == 1)
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{
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quot = a;
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rem = 0;
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} else
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{
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quot = (mp_limb_t) ((double) a * npre);
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rem = a - quot * n;
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}
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if (rem < (mp_limb_signed_t) (-n))
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quot -= (mp_limb_t) ((double) (-rem) * npre);
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else if (rem >= (slong) n)
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quot += (mp_limb_t) ((double) rem * npre);
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else if (rem < WORD(0))
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return rem + n;
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else
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return rem;
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rem = a - quot * n;
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if (rem >= (slong) n)
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return rem - n;
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else if (rem < WORD(0))
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return rem + n;
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else
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return rem;
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}
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