102 lines
2.6 KiB
C
102 lines
2.6 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) 2013 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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/*
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TODO: speedup mpir's mullow and mulhigh and use instead of mul/mul_n
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*/
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void flint_mpn_mod_preinvn(mp_ptr rp, mp_srcptr ap, mp_size_t m,
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mp_srcptr d, mp_size_t n, mp_srcptr dinv)
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{
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mp_limb_t cy;
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mp_ptr t, r, a;
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mp_size_t size;
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TMP_INIT;
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a = (mp_ptr) ap + m - 2*n;
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r = rp + m - 2*n;
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/* check if top n limbs of a exceed d */
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if (mpn_cmp(a + n, d, n) >= 0)
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mpn_sub_n(r + n, a + n, d, n);
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else if (r != a)
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mpn_copyi(r + n, a + n, n);
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TMP_START;
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t = TMP_ALLOC(3*n*sizeof(mp_limb_t));
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/* 2n by n division */
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while (m >= 2*n)
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{
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mpn_mul_n(t, dinv, r + n, n);
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cy = mpn_add_n(t + 2*n, t + n, r + n, n);
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mpn_mul_n(t, d, t + 2*n, n);
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cy = r[n] - t[n] - mpn_sub_n(r, a, t, n);
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while (cy > 0)
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cy -= mpn_sub_n(r, r, d, n);
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if (mpn_cmp(r, d, n) >= 0)
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mpn_sub_n(r, r, d, n);
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m -= n;
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r -= n;
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a -= n;
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}
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size = m - n;
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/* m by n division with 2n > m > n */
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if (size)
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{
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if (rp != ap)
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mpn_copyi(rp, ap, size);
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mpn_mul(t, dinv, n, rp + n, size);
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cy = mpn_add_n(t + 2*n, t + n, rp + n, size);
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mpn_mul(t, d, n, t + 2*n, size);
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if (cy)
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mpn_add_n(t + size, t + size, d, n + 1 - size);
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cy = rp[n] - t[n] - mpn_sub_n(rp, rp, t, n);
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while (cy > 0)
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cy -= mpn_sub_n(rp, rp, d, n);
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if (mpn_cmp(rp, d, n) >= 0)
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mpn_sub_n(rp, rp, d, n);
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}
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TMP_END;
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}
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