toom_eval_pm1.c
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上传日期:2022-08-06
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- /* mpn_toom_eval_pm1 -- Evaluate a polynomial in +1 and -1
- Contributed to the GNU project by Niels M鰈ler
- 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 "gmp.h"
- #include "gmp-impl.h"
- /* Evaluates a polynomial of degree k > 3, in the points +1 and -1. */
- int
- mpn_toom_eval_pm1 (mp_ptr xp1, mp_ptr xm1, unsigned k,
- mp_srcptr xp, mp_size_t n, mp_size_t hn, mp_ptr tp)
- {
- unsigned i;
- int neg;
- ASSERT (k >= 4);
- 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. */
- xp1[n] = mpn_add_n (xp1, xp, xp + 2*n, n);
- for (i = 4; i < k; i += 2)
- ASSERT_NOCARRY (mpn_add (xp1, xp1, n+1, xp+i*n, n));
- tp[n] = mpn_add_n (tp, xp + n, xp + 3*n, n);
- for (i = 5; i < k; i += 2)
- ASSERT_NOCARRY (mpn_add (tp, tp, n+1, xp+i*n, n));
- if (k & 1)
- ASSERT_NOCARRY (mpn_add (tp, tp, n+1, xp+k*n, hn));
- else
- ASSERT_NOCARRY (mpn_add (xp1, xp1, n+1, xp+k*n, hn));
- neg = (mpn_cmp (xp1, tp, n + 1) < 0) ? ~0 : 0;
- #if HAVE_NATIVE_mpn_add_n_sub_n
- if (neg)
- mpn_add_n_sub_n (xp1, xm1, tp, xp1, n + 1);
- else
- mpn_add_n_sub_n (xp1, xm1, xp1, tp, n + 1);
- #else
- if (neg)
- mpn_sub_n (xm1, tp, xp1, n + 1);
- else
- mpn_sub_n (xm1, xp1, tp, n + 1);
- mpn_add_n (xp1, xp1, tp, n + 1);
- #endif
- ASSERT (xp1[n] <= k);
- ASSERT (xm1[n] <= k/2 + 1);
- return neg;
- }