118 lines
3.5 KiB
C
118 lines
3.5 KiB
C
/* mpn_toom_eval_pm2exp -- Evaluate a polynomial in +2^k and -2^k
|
|
|
|
Contributed to the GNU project by Niels Möller
|
|
|
|
THE FUNCTION IN THIS FILE IS INTERNAL WITH A MUTABLE INTERFACE. IT IS ONLY
|
|
SAFE TO REACH IT THROUGH DOCUMENTED INTERFACES. IN FACT, IT IS ALMOST
|
|
GUARANTEED THAT IT WILL CHANGE OR DISAPPEAR IN A FUTURE GNU MP RELEASE.
|
|
|
|
Copyright 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 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 "mpir.h"
|
|
#include "gmp-impl.h"
|
|
|
|
/* Evaluates a polynomial of degree k > 2, in the points +2^shift and -2^shift. */
|
|
int
|
|
mpn_toom_eval_pm2exp (mp_ptr xp2, mp_ptr xm2, unsigned k,
|
|
mp_srcptr xp, mp_size_t n, mp_size_t hn, unsigned shift,
|
|
mp_ptr tp)
|
|
{
|
|
unsigned i;
|
|
int neg;
|
|
#if HAVE_NATIVE_mpn_addlsh_n
|
|
mp_limb_t cy;
|
|
#endif
|
|
|
|
ASSERT (k >= 3);
|
|
ASSERT (shift*k < GMP_NUMB_BITS);
|
|
|
|
ASSERT (hn > 0);
|
|
ASSERT (hn <= n);
|
|
|
|
/* The degree k is also the number of full-size coefficients, so
|
|
* that last coefficient, of size hn, starts at xp + k*n. */
|
|
|
|
#if HAVE_NATIVE_mpn_addlsh_n
|
|
xp2[n] = mpn_addlsh_n (xp2, xp, xp + 2*n, n, 2*shift);
|
|
for (i = 4; i < k; i += 2)
|
|
xp2[n] += mpn_addlsh_n (xp2, xp2, xp + i*n, n, i*shift);
|
|
|
|
tp[n] = mpn_lshift (tp, xp+n, n, shift);
|
|
for (i = 3; i < k; i+= 2)
|
|
tp[n] += mpn_addlsh_n (tp, tp, xp+i*n, n, i*shift);
|
|
|
|
if (k & 1)
|
|
{
|
|
cy = mpn_addlsh_n (tp, tp, xp+k*n, hn, k*shift);
|
|
MPN_INCR_U (tp + hn, n+1 - hn, cy);
|
|
}
|
|
else
|
|
{
|
|
cy = mpn_addlsh_n (xp2, xp2, xp+k*n, hn, k*shift);
|
|
MPN_INCR_U (xp2 + hn, n+1 - hn, cy);
|
|
}
|
|
|
|
#else /* !HAVE_NATIVE_mpn_addlsh_n */
|
|
xp2[n] = mpn_lshift (tp, xp+2*n, n, 2*shift);
|
|
xp2[n] += mpn_add_n (xp2, xp, tp, n);
|
|
for (i = 4; i < k; i += 2)
|
|
{
|
|
xp2[n] += mpn_lshift (tp, xp + i*n, n, i*shift);
|
|
xp2[n] += mpn_add_n (xp2, xp2, tp, n);
|
|
}
|
|
|
|
tp[n] = mpn_lshift (tp, xp+n, n, shift);
|
|
for (i = 3; i < k; i+= 2)
|
|
{
|
|
tp[n] += mpn_lshift (xm2, xp + i*n, n, i*shift);
|
|
tp[n] += mpn_add_n (tp, tp, xm2, n);
|
|
}
|
|
|
|
xm2[hn] = mpn_lshift (xm2, xp + k*n, hn, k*shift);
|
|
if (k & 1)
|
|
mpn_add (tp, tp, n+1, xm2, hn+1);
|
|
else
|
|
mpn_add (xp2, xp2, n+1, xm2, hn+1);
|
|
#endif /* !HAVE_NATIVE_mpn_addlsh_n */
|
|
|
|
neg = (mpn_cmp (xp2, tp, n + 1) < 0) ? ~0 : 0;
|
|
|
|
#if HAVE_NATIVE_mpn_sumdiff_n
|
|
if (neg)
|
|
mpn_sumdiff_n (xp2, xm2, tp, xp2, n + 1);
|
|
else
|
|
mpn_sumdiff_n (xp2, xm2, xp2, tp, n + 1);
|
|
#else
|
|
if (neg)
|
|
mpn_sub_n (xm2, tp, xp2, n + 1);
|
|
else
|
|
mpn_sub_n (xm2, xp2, tp, n + 1);
|
|
|
|
mpn_add_n (xp2, xp2, tp, n + 1);
|
|
#endif
|
|
|
|
/* FIXME: the following asserts are useless if (k+1)*shift >= GMP_LIMB_BITS */
|
|
ASSERT ((k+1)*shift >= GMP_LIMB_BITS ||
|
|
xp2[n] < ((CNST_LIMB(1)<<((k+1)*shift))-1)/((CNST_LIMB(1)<<shift)-1));
|
|
ASSERT ((k+2)*shift >= GMP_LIMB_BITS ||
|
|
xm2[n] < ((CNST_LIMB(1)<<((k+2)*shift))-((k&1)?(CNST_LIMB(1)<<shift):1))/((CNST_LIMB(1)<<(2*shift))-1));
|
|
|
|
return neg;
|
|
}
|