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/* mpn_dc_bdiv_q -- divide-and-conquer Hensel division with precomputed
inverse, returning quotient.
Contributed to the GNU project by Niels Mller and Torbjrn Granlund.
THE FUNCTIONS IN THIS FILE ARE INTERNAL WITH A MUTABLE INTERFACE. IT IS
ONLY SAFE TO REACH THEM THROUGH DOCUMENTED INTERFACES. IN FACT, IT IS
ALMOST GUARANTEED THAT THEY WILL CHANGE OR DISAPPEAR IN A FUTURE GMP
RELEASE.
Copyright 2006, 2007 Free Software Foundation, Inc.
This file is part of the GNU MP Library.
The GNU MP Library is free software; you can redistribute it and/or modify
it under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation; either version 3 of the License, or (at your
option) any later version.
The GNU MP Library is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
License for more details.
You should have received a copy of the GNU Lesser General Public License
along with the GNU MP Library. If not, see http://www.gnu.org/licenses/. */
#include "gmp.h"
#include "gmp-impl.h"
/* Computes Q = N / D mod B^n, destroys N. */
mp_size_t
mpn_dc_bdiv_q_n_itch (mp_size_t n)
{
/* NOTE: Depends om mullow_n interface */
return n;
}
void
mpn_dc_bdiv_q_n (mp_ptr qp,
mp_ptr np, mp_srcptr dp, mp_size_t n,
mp_limb_t dinv, mp_ptr tp)
{
while (ABOVE_THRESHOLD (n, DC_BDIV_Q_THRESHOLD))
{
mp_limb_t l, h;
mp_limb_t cy;
l = n >> 1;
h = n - l;
cy = mpn_dc_bdiv_qr_n (qp, np, dp, l, dinv, tp);
mpn_mullow_n (tp, qp, dp + h, l);
mpn_sub_n (np + h, np + h, tp, l);
if (l < h)
{
cy += mpn_submul_1 (np + l, qp, l, dp[l]);
np[n - 1] -= cy;
}
qp += l;
np += l;
n -= l;
}
mpn_sb_bdiv_q (qp, np, n, dp, n, dinv);
}
void
mpn_dc_bdiv_q (mp_ptr qp,
mp_ptr np, mp_size_t nn,
mp_srcptr dp, mp_size_t dn,
mp_limb_t dinv)
{
mp_size_t qn;
mp_limb_t cy;
mp_ptr tp;
TMP_DECL;
TMP_MARK;
tp = TMP_SALLOC_LIMBS (dn);
qn = nn;
if (qn > dn)
{
/* Reduce qn mod dn in a super-efficient manner. */
do
qn -= dn;
while (qn > dn);
/* Perform the typically smaller block first. */
if (BELOW_THRESHOLD (qn, DC_BDIV_QR_THRESHOLD))
cy = mpn_sb_bdiv_qr (qp, np, 2 * qn, dp, qn, dinv);
else
cy = mpn_dc_bdiv_qr_n (qp, np, dp, qn, dinv, tp);
if (qn != dn)
{
if (qn > dn - qn)
mpn_mul (tp, qp, qn, dp + qn, dn - qn);
else
mpn_mul (tp, dp + qn, dn - qn, qp, qn);
mpn_incr_u (tp + qn, cy);
mpn_sub (np + qn, np + qn, nn - qn, tp, dn);
cy = 0;
}
np += qn;
qp += qn;
qn = nn - qn;
while (qn > dn)
{
mpn_sub_1 (np + dn, np + dn, qn, cy);
cy = mpn_dc_bdiv_qr_n (qp, np, dp, dn, dinv, tp);
qp += dn;
np += dn;
qn -= dn;
}
mpn_sub_1 (np + dn, np + dn, qn, cy);
mpn_dc_bdiv_q_n (qp, np, dp, dn, dinv, tp);
TMP_FREE;
return;
}
if (BELOW_THRESHOLD (qn, DC_BDIV_Q_THRESHOLD))
mpn_sb_bdiv_q (qp, np, 2 * qn, dp, qn, dinv);
else
mpn_dc_bdiv_q_n (qp, np, dp, qn, dinv, tp);
TMP_FREE;
}
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