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b58ddff026
* merged mpfr 3.0.0 and gmp 5.0.1 in buildtools trunk git-svn-id: file:///srv/svn/repos/haiku/buildtools/trunk@37378 a95241bf-73f2-0310-859d-f6bbb57e9c96
88 lines
2.3 KiB
C
88 lines
2.3 KiB
C
/* mpn_sbpi1_bdiv_q -- schoolbook Hensel division with precomputed inverse,
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returning quotient only.
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Contributed to the GNU project by Niels Möller.
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THE FUNCTIONS IN THIS FILE ARE INTERNAL FUNCTIONS WITH MUTABLE INTERFACES.
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IT IS ONLY SAFE TO REACH THEM THROUGH DOCUMENTED INTERFACES. IN FACT, IT IS
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ALMOST GUARANTEED THAT THEY'LL CHANGE OR DISAPPEAR IN A FUTURE GMP RELEASE.
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Copyright 2005, 2006, 2009 Free Software Foundation, Inc.
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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 "gmp.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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D must be odd. dinv is (-D)^-1 mod B.
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The straightforward way to compute Q is to cancel one limb at a time, using
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qp[i] = D^{-1} * np[i] (mod B)
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N -= B^i * qp[i] * D
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But we prefer addition to subtraction, since mpn_addmul_1 is often faster
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than mpn_submul_1. Q = - N / D can be computed by iterating
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qp[i] = (-D)^{-1} * np[i] (mod B)
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N += B^i * qp[i] * D
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And then we flip the sign, -Q = (not Q) + 1. */
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void
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mpn_sbpi1_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 i;
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mp_limb_t cy, q;
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ASSERT (dn > 0);
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ASSERT (nn >= dn);
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ASSERT ((dp[0] & 1) != 0);
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for (i = nn - dn; i > 0; i--)
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{
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q = dinv * np[0];
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qp[0] = ~q;
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qp++;
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cy = mpn_addmul_1 (np, dp, dn, q);
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mpn_add_1 (np + dn, np + dn, i, cy);
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ASSERT (np[0] == 0);
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np++;
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}
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for (i = dn; i > 1; i--)
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{
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q = dinv * np[0];
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qp[0] = ~q;
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qp++;
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mpn_addmul_1 (np, dp, i, q);
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ASSERT (np[0] == 0);
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np++;
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}
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/* Final limb */
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q = dinv * np[0];
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qp[0] = ~q;
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mpn_add_1 (qp - nn + 1, qp - nn + 1, nn, 1);
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}
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