2010-03-02 16:09:03 -05:00
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/* mpn_dc_bdiv_q -- divide-and-conquer Hensel division with precomputed
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inverse, returning quotient.
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Contributed to the GNU project by Niels M<EFBFBD>ller and Torbjorn Granlund.
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THE FUNCTIONS IN THIS FILE ARE INTERNAL WITH MUTABLE INTERFACES. IT IS ONLY
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SAFE TO REACH THEM THROUGH DOCUMENTED INTERFACES. IN FACT, IT IS ALMOST
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GUARANTEED THAT THEY WILL CHANGE OR DISAPPEAR IN A FUTURE GMP RELEASE.
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Copyright 2006, 2007, 2009, 2010 Free Software Foundation, Inc.
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2010-03-14 18:42:55 -04:00
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Copyright 2010 William Hart (minor modifications)
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2010-03-02 16:09:03 -05:00
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This file is part of the GNU MP Library.
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The GNU MP Library is free software; you can redistribute it and/or modify
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it under the terms of the GNU Lesser General Public License as published by
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the Free Software Foundation; either version 3 of the License, or (at your
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option) any later version.
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The GNU MP Library is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
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or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
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License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with the GNU MP Library. If not, see http://www.gnu.org/licenses/. */
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#include "mpir.h"
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#include "gmp-impl.h"
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/* Computes Q = N / D mod B^nn, destroys N.
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N = {np,nn}
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D = {dp,dn}
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*/
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void
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mpn_dc_bdiv_q (mp_ptr qp,
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mp_ptr np, mp_size_t nn,
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mp_srcptr dp, mp_size_t dn,
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mp_limb_t dinv)
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{
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mp_size_t qn;
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mp_limb_t cy, wp[2];
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mp_ptr tp;
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TMP_DECL;
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TMP_MARK;
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2010-03-16 12:05:48 -04:00
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ASSERT (dn >= 6);
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2010-03-02 16:09:03 -05:00
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ASSERT (nn - dn >= 0);
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ASSERT (dp[0] & 1);
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2010-03-02 16:29:35 -05:00
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tp = TMP_ALLOC_LIMBS (MAX(dn, DC_BDIV_Q_N_ITCH(dn)));
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2010-03-02 16:09:03 -05:00
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qn = nn;
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if (qn > dn)
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{
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/* Reduce qn mod dn in a super-efficient manner. */
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do
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qn -= dn;
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while (qn > dn);
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/* Perform the typically smaller block first. */
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if (BELOW_THRESHOLD (qn, DC_BDIV_QR_THRESHOLD))
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cy = mpn_sb_bdiv_qr (qp, np, 2 * qn, dp, qn, dinv);
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else
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cy = mpn_dc_bdiv_qr_n (qp, np, dp, qn, dinv, tp);
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if (qn != dn)
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{
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if (qn > dn - qn)
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mpn_mul (tp, qp, qn, dp + qn, dn - qn);
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else
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mpn_mul (tp, dp + qn, dn - qn, qp, qn);
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mpn_incr_u (tp + qn, cy);
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mpn_sub (np + qn, np + qn, nn - qn, tp, dn);
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cy = 0;
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}
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np += qn;
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qp += qn;
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qn = nn - qn;
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while (qn > dn)
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{
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mpn_sub_1 (np + dn, np + dn, qn, cy);
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cy = mpn_dc_bdiv_qr_n (qp, np, dp, dn, dinv, tp);
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qp += dn;
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np += dn;
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qn -= dn;
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}
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mpn_dc_bdiv_q_n (qp, wp, np, dp, dn, dinv, tp);
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}
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else
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{
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if (BELOW_THRESHOLD (qn, DC_BDIV_Q_THRESHOLD))
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mpn_sb_bdiv_q (qp, wp, np, qn, dp, qn, dinv);
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else
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mpn_dc_bdiv_q_n (qp, wp, np, dp, qn, dinv, tp);
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}
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TMP_FREE;
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}
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