61 lines
1.7 KiB
C
61 lines
1.7 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 William Hart
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******************************************************************************/
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#include <stdlib.h>
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#include <gmp.h>
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#include "flint.h"
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#include "longlong.h"
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#include "mpn_extras.h"
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mp_limb_t flint_mpn_preinv1(mp_limb_t d1, mp_limb_t d2)
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{
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mp_limb_t q, r[2], p[2], cy;
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if (d2 + 1 == 0 && d1 + 1 == 0)
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return 0;
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if (d1 + 1 == 0)
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q = ~d1, r[1] = ~d2;
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else
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udiv_qrnnd(q, r[1], ~d1, ~d2, d1 + 1);
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if (d2 + 1 == 0)
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return q;
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r[0] = 0;
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umul_ppmm(p[1], p[0], q, ~d2);
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cy = mpn_add_n(r, r, p, 2);
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p[0] = d2 + 1, p[1] = d1 + (d2 + 1 == 0);
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while (cy || mpn_cmp(r, p, 2) >= 0)
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{
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q++;
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cy -= mpn_sub_n(r, r, p, 2);
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}
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return q;
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}
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