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Added GMP mpz_divexact code to MPIR.

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This commit is contained in:
(no author) 2010-03-04 17:12:43 +00:00
parent 5795eacd2f
commit 774f47e08f
1 changed files with 31 additions and 85 deletions
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116
mpz/divexact.c
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@ -1,13 +1,15 @@
/* mpz_divexact -- finds quotient when known that quot * den == num && den != 0.
Copyright 1991, 1993, 1994, 1995, 1996, 1997, 1998, 2000, 2001, 2002, 2005, 2006
Free Software Foundation, Inc.
Contributed to the GNU project by Niels Möller.
Copyright 1991, 1993, 1994, 1995, 1996, 1997, 1998, 2000, 2001, 2002, 2005,
2006, 2007, 2009 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 2.1 of the License, or (at your
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
@ -16,20 +18,8 @@ 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; see the file COPYING.LIB. If not, write to
the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
MA 02110-1301, USA. */
along with the GNU MP Library. If not, see http://www.gnu.org/licenses/. */
/* Ken Weber (kweber@mat.ufrgs.br, kweber@mcs.kent.edu)
Funding for this work has been partially provided by Conselho Nacional
de Desenvolvimento Cienti'fico e Tecnolo'gico (CNPq) do Brazil, Grant
301314194-2, and was done while I was a visiting reseacher in the Instituto
de Matema'tica at Universidade Federal do Rio Grande do Sul (UFRGS).
References:
T. Jebelean, An algorithm for exact division, Journal of Symbolic
Computation, v. 15, 1993, pp. 169-180. */
#include "mpir.h"
#include "gmp-impl.h"
@ -38,10 +28,10 @@ MA 02110-1301, USA. */
void
mpz_divexact (mpz_ptr quot, mpz_srcptr num, mpz_srcptr den)
{
mp_ptr qp, tp;
mp_size_t qsize, tsize;
mp_ptr qp;
mp_size_t qn;
mp_srcptr np, dp;
mp_size_t nsize, dsize;
mp_size_t nn, dn;
TMP_DECL;
#if WANT_ASSERT
@ -54,82 +44,38 @@ mpz_divexact (mpz_ptr quot, mpz_srcptr num, mpz_srcptr den)
}
#endif
nsize = ABS (num->_mp_size);
dsize = ABS (den->_mp_size);
nn = ABSIZ (num);
dn = ABSIZ (den);
qsize = nsize - dsize + 1;
if (quot->_mp_alloc < qsize)
_mpz_realloc (quot, qsize);
qn = nn - dn + 1;
MPZ_REALLOC (quot, qn);
np = num->_mp_d;
dp = den->_mp_d;
qp = quot->_mp_d;
if (nsize == 0)
if (nn < dn)
{
if (dsize == 0)
DIVIDE_BY_ZERO;
quot->_mp_size = 0;
return;
}
if (dsize <= 1)
{
if (dsize == 1)
{
MPN_DIVREM_OR_DIVEXACT_1 (qp, np, nsize, dp[0]);
qsize -= qp[qsize - 1] == 0;
quot->_mp_size = (num->_mp_size ^ den->_mp_size) >= 0 ? qsize : -qsize;
return;
}
/* Generate divide-by-zero error since dsize == 0. */
DIVIDE_BY_ZERO;
}
/* Avoid quadratic behaviour, but do it conservatively. */
if (qsize > 1500)
{
mpz_tdiv_q (quot, num, den);
/* This special case avoids segfaults below when the function is
incorrectly called with |N| < |D|, N != 0. It also handles the
well-defined case N = 0. */
SIZ(quot) = 0;
return;
}
TMP_MARK;
/* QUOT <-- NUM/2^r, T <-- DEN/2^r where = r number of twos in DEN. */
while (dp[0] == 0)
np += 1, nsize -= 1, dp += 1, dsize -= 1;
tsize = MIN (qsize, dsize);
if ((dp[0] & 1) != 0)
{
if (quot == den) /* QUOT and DEN overlap. */
{
tp = (mp_ptr) TMP_ALLOC (tsize * BYTES_PER_MP_LIMB);
MPN_COPY (tp, dp, tsize);
}
else
tp = (mp_ptr) dp;
if (qp != np)
MPN_COPY_INCR (qp, np, qsize);
}
else
{
unsigned int r;
tp = (mp_ptr) TMP_ALLOC (tsize * BYTES_PER_MP_LIMB);
count_trailing_zeros (r, dp[0]);
mpn_rshift (tp, dp, tsize, r);
if (dsize > tsize)
tp[tsize - 1] |= (dp[tsize] << (GMP_NUMB_BITS - r)) & GMP_NUMB_MASK;
mpn_rshift (qp, np, qsize, r);
if (nsize > qsize)
qp[qsize - 1] |= (np[qsize] << (GMP_NUMB_BITS - r)) & GMP_NUMB_MASK;
}
qp = PTR(quot);
/* Now QUOT <-- QUOT/T. */
mpn_bdivmod (qp, qp, qsize, tp, tsize, qsize * GMP_NUMB_BITS);
MPN_NORMALIZE (qp, qsize);
if (quot == num || quot == den)
qp = TMP_ALLOC_LIMBS (qn);
quot->_mp_size = (num->_mp_size ^ den->_mp_size) >= 0 ? qsize : -qsize;
np = PTR(num);
dp = PTR(den);
mpn_divexact (qp, np, nn, dp, dn);
MPN_NORMALIZE (qp, qn);
SIZ(quot) = (SIZ(num) ^ SIZ(den)) >= 0 ? qn : -qn;
if (qp != PTR(quot))
MPN_COPY (PTR(quot), qp, qn);
TMP_FREE;
}