80 lines
2.3 KiB
C
80 lines
2.3 KiB
C
/* mpn_toom_eval_pm1 -- Evaluate a polynomial in +1 and -1
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Contributed to the GNU project by Niels Möller
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THE FUNCTION IN THIS FILE IS INTERNAL WITH A MUTABLE INTERFACE. IT IS ONLY
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SAFE TO REACH IT THROUGH DOCUMENTED INTERFACES. IN FACT, IT IS ALMOST
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GUARANTEED THAT IT WILL CHANGE OR DISAPPEAR IN A FUTURE GNU MP RELEASE.
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Copyright 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 "mpir.h"
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#include "gmp-impl.h"
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/* Evaluates a polynomial of degree k > 3, in the points +1 and -1. */
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int
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mpn_toom_eval_pm1 (mp_ptr xp1, mp_ptr xm1, unsigned k,
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mp_srcptr xp, mp_size_t n, mp_size_t hn, mp_ptr tp)
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{
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unsigned i;
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int neg;
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ASSERT (k >= 4);
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ASSERT (hn > 0);
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ASSERT (hn <= n);
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/* The degree k is also the number of full-size coefficients, so
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* that last coefficient, of size hn, starts at xp + k*n. */
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xp1[n] = mpn_add_n (xp1, xp, xp + 2*n, n);
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for (i = 4; i < k; i += 2)
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ASSERT_NOCARRY (mpn_add (xp1, xp1, n+1, xp+i*n, n));
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tp[n] = mpn_add_n (tp, xp + n, xp + 3*n, n);
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for (i = 5; i < k; i += 2)
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ASSERT_NOCARRY (mpn_add (tp, tp, n+1, xp+i*n, n));
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if (k & 1)
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ASSERT_NOCARRY (mpn_add (tp, tp, n+1, xp+k*n, hn));
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else
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ASSERT_NOCARRY (mpn_add (xp1, xp1, n+1, xp+k*n, hn));
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neg = (mpn_cmp (xp1, tp, n + 1) < 0) ? ~0 : 0;
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#if HAVE_NATIVE_mpn_add_n_sub_n
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if (neg)
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mpn_add_n_sub_n (xp1, xm1, tp, xp1, n + 1);
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else
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mpn_add_n_sub_n (xp1, xm1, xp1, tp, n + 1);
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#else
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if (neg)
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mpn_sub_n (xm1, tp, xp1, n + 1);
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else
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mpn_sub_n (xm1, xp1, tp, n + 1);
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mpn_add_n (xp1, xp1, tp, n + 1);
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#endif
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ASSERT (xp1[n] <= k);
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ASSERT (xm1[n] <= k/2 + 1);
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return neg;
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}
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