dcpi1_bdiv_q.c
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- /* mpn_dcpi1_bdiv_q -- divide-and-conquer Hensel division with precomputed
- inverse, returning quotient.
- Contributed to the GNU project by Niels M鰈ler and Torbjorn Granlund.
- THE FUNCTIONS IN THIS FILE ARE INTERNAL WITH MUTABLE INTERFACES. 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, 2009, 2010 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"
- mp_size_t
- mpn_dcpi1_bdiv_q_n_itch (mp_size_t n)
- {
- /* NOTE: Depends on mullo_n interface */
- return n;
- }
- /* Computes Q = N / D mod B^n, destroys N.
- N = {np,n}
- D = {dp,n}
- */
- void
- mpn_dcpi1_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_size_t lo, hi;
- mp_limb_t cy;
- lo = n >> 1; /* floor(n/2) */
- hi = n - lo; /* ceil(n/2) */
- cy = mpn_dcpi1_bdiv_qr_n (qp, np, dp, lo, dinv, tp);
- mpn_mullo_n (tp, qp, dp + hi, lo);
- mpn_sub_n (np + hi, np + hi, tp, lo);
- if (lo < hi)
- {
- cy += mpn_submul_1 (np + lo, qp, lo, dp[lo]);
- np[n - 1] -= cy;
- }
- qp += lo;
- np += lo;
- n -= lo;
- }
- mpn_sbpi1_bdiv_q (qp, np, n, dp, n, dinv);
- }
- /* Computes Q = N / D mod B^nn, destroys N.
- N = {np,nn}
- D = {dp,dn}
- */
- void
- mpn_dcpi1_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;
- ASSERT (dn >= 2);
- ASSERT (nn - dn >= 0);
- ASSERT (dp[0] & 1);
- 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_sbpi1_bdiv_qr (qp, np, 2 * qn, dp, qn, dinv);
- else
- cy = mpn_dcpi1_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_dcpi1_bdiv_qr_n (qp, np, dp, dn, dinv, tp);
- qp += dn;
- np += dn;
- qn -= dn;
- }
- mpn_dcpi1_bdiv_q_n (qp, np, dp, dn, dinv, tp);
- }
- else
- {
- if (BELOW_THRESHOLD (qn, DC_BDIV_Q_THRESHOLD))
- mpn_sbpi1_bdiv_q (qp, np, qn, dp, qn, dinv);
- else
- mpn_dcpi1_bdiv_q_n (qp, np, dp, qn, dinv, tp);
- }
- TMP_FREE;
- }