/src/libgmp/mpn/toom_eval_dgr3_pm1.c
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1 | | /* mpn_toom_eval_dgr3_pm1 -- Evaluate a degree 3 polynomial in +1 and -1 |
2 | | |
3 | | Contributed to the GNU project by Niels Möller |
4 | | |
5 | | THE FUNCTION IN THIS FILE IS INTERNAL WITH A MUTABLE INTERFACE. IT IS ONLY |
6 | | SAFE TO REACH IT THROUGH DOCUMENTED INTERFACES. IN FACT, IT IS ALMOST |
7 | | GUARANTEED THAT IT WILL CHANGE OR DISAPPEAR IN A FUTURE GNU MP RELEASE. |
8 | | |
9 | | Copyright 2009 Free Software Foundation, Inc. |
10 | | |
11 | | This file is part of the GNU MP Library. |
12 | | |
13 | | The GNU MP Library is free software; you can redistribute it and/or modify |
14 | | it under the terms of either: |
15 | | |
16 | | * the GNU Lesser General Public License as published by the Free |
17 | | Software Foundation; either version 3 of the License, or (at your |
18 | | option) any later version. |
19 | | |
20 | | or |
21 | | |
22 | | * the GNU General Public License as published by the Free Software |
23 | | Foundation; either version 2 of the License, or (at your option) any |
24 | | later version. |
25 | | |
26 | | or both in parallel, as here. |
27 | | |
28 | | The GNU MP Library is distributed in the hope that it will be useful, but |
29 | | WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY |
30 | | or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
31 | | for more details. |
32 | | |
33 | | You should have received copies of the GNU General Public License and the |
34 | | GNU Lesser General Public License along with the GNU MP Library. If not, |
35 | | see https://www.gnu.org/licenses/. */ |
36 | | |
37 | | |
38 | | #include "gmp-impl.h" |
39 | | |
40 | | /* Evaluates a polynomial of degree 3, in the points +1 and -1. */ |
41 | | /* It returns 0 or ~0, depending on the sign of the result xm1. */ |
42 | | unsigned |
43 | | mpn_toom_eval_dgr3_pm1 (mp_ptr xp1, mp_ptr xm1, |
44 | | mp_srcptr xp, mp_size_t n, mp_size_t x3n, mp_ptr tp) |
45 | 2.33k | { |
46 | 2.33k | unsigned neg; |
47 | | |
48 | 2.33k | ASSERT (x3n > 0); |
49 | 2.33k | ASSERT (x3n <= n); |
50 | | |
51 | 2.33k | xp1[n] = mpn_add_n (xp1, xp, xp + 2*n, n); |
52 | 2.33k | tp[n] = mpn_add (tp, xp + n, n, xp + 3*n, x3n); |
53 | | |
54 | 2.33k | neg = - (unsigned) (mpn_cmp (xp1, tp, n + 1) < 0); |
55 | | |
56 | | #if HAVE_NATIVE_mpn_add_n_sub_n |
57 | | if (neg) |
58 | | mpn_add_n_sub_n (xp1, xm1, tp, xp1, n + 1); |
59 | | else |
60 | | mpn_add_n_sub_n (xp1, xm1, xp1, tp, n + 1); |
61 | | #else |
62 | 2.33k | if (neg) |
63 | 432 | mpn_sub_n (xm1, tp, xp1, n + 1); |
64 | 1.90k | else |
65 | 1.90k | mpn_sub_n (xm1, xp1, tp, n + 1); |
66 | | |
67 | 2.33k | mpn_add_n (xp1, xp1, tp, n + 1); |
68 | 2.33k | #endif |
69 | | |
70 | 2.33k | ASSERT (xp1[n] <= 3); |
71 | 2.33k | ASSERT (xm1[n] <= 1); |
72 | | |
73 | 2.33k | return neg; |
74 | 2.33k | } |