/src/gmp/mpn/toom_eval_pm2.c
Line | Count | Source (jump to first uncovered line) |
1 | | /* mpn_toom_eval_pm2 -- Evaluate a polynomial in +2 and -2 |
2 | | |
3 | | Contributed to the GNU project by Niels Möller and Marco Bodrato |
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 | | #include "gmp-impl.h" |
38 | | |
39 | | /* DO_addlsh2(d,a,b,n,cy) computes cy,{d,n} <- {a,n} + 4*(cy,{b,n}), it |
40 | | can be used as DO_addlsh2(d,a,d,n,d[n]), for accumulation on {d,n+1}. */ |
41 | | #if HAVE_NATIVE_mpn_addlsh2_n |
42 | 0 | #define DO_addlsh2(d, a, b, n, cy) \ |
43 | 0 | do { \ |
44 | 0 | (cy) <<= 2; \ |
45 | 0 | (cy) += mpn_addlsh2_n(d, a, b, n); \ |
46 | 0 | } while (0) |
47 | | #else |
48 | | #if HAVE_NATIVE_mpn_addlsh_n |
49 | | #define DO_addlsh2(d, a, b, n, cy) \ |
50 | | do { \ |
51 | | (cy) <<= 2; \ |
52 | | (cy) += mpn_addlsh_n(d, a, b, n, 2); \ |
53 | | } while (0) |
54 | | #else |
55 | | /* The following is not a general substitute for addlsh2. |
56 | | It is correct if d == b, but it is not if d == a. */ |
57 | | #define DO_addlsh2(d, a, b, n, cy) \ |
58 | | do { \ |
59 | | (cy) <<= 2; \ |
60 | | (cy) += mpn_lshift(d, b, n, 2); \ |
61 | | (cy) += mpn_add_n(d, d, a, n); \ |
62 | | } while (0) |
63 | | #endif |
64 | | #endif |
65 | | |
66 | | /* Evaluates a polynomial of degree 2 < k < GMP_NUMB_BITS, in the |
67 | | points +2 and -2. */ |
68 | | int |
69 | | mpn_toom_eval_pm2 (mp_ptr xp2, mp_ptr xm2, unsigned k, |
70 | | mp_srcptr xp, mp_size_t n, mp_size_t hn, mp_ptr tp) |
71 | 0 | { |
72 | 0 | int i; |
73 | 0 | int neg; |
74 | 0 | mp_limb_t cy; |
75 | |
|
76 | 0 | ASSERT (k >= 3); |
77 | 0 | ASSERT (k < GMP_NUMB_BITS); |
78 | |
|
79 | 0 | ASSERT (hn > 0); |
80 | 0 | ASSERT (hn <= n); |
81 | | |
82 | | /* The degree k is also the number of full-size coefficients, so |
83 | | * that last coefficient, of size hn, starts at xp + k*n. */ |
84 | |
|
85 | 0 | cy = 0; |
86 | 0 | DO_addlsh2 (xp2, xp + (k-2) * n, xp + k * n, hn, cy); |
87 | 0 | if (hn != n) |
88 | 0 | cy = mpn_add_1 (xp2 + hn, xp + (k-2) * n + hn, n - hn, cy); |
89 | 0 | for (i = k - 4; i >= 0; i -= 2) |
90 | 0 | DO_addlsh2 (xp2, xp + i * n, xp2, n, cy); |
91 | 0 | xp2[n] = cy; |
92 | |
|
93 | 0 | k--; |
94 | |
|
95 | 0 | cy = 0; |
96 | 0 | DO_addlsh2 (tp, xp + (k-2) * n, xp + k * n, n, cy); |
97 | 0 | for (i = k - 4; i >= 0; i -= 2) |
98 | 0 | DO_addlsh2 (tp, xp + i * n, tp, n, cy); |
99 | 0 | tp[n] = cy; |
100 | |
|
101 | 0 | if (k & 1) |
102 | 0 | ASSERT_NOCARRY(mpn_lshift (tp , tp , n + 1, 1)); |
103 | 0 | else |
104 | 0 | ASSERT_NOCARRY(mpn_lshift (xp2, xp2, n + 1, 1)); |
105 | |
|
106 | 0 | neg = (mpn_cmp (xp2, tp, n + 1) < 0) ? ~0 : 0; |
107 | |
|
108 | | #if HAVE_NATIVE_mpn_add_n_sub_n |
109 | | if (neg) |
110 | | mpn_add_n_sub_n (xp2, xm2, tp, xp2, n + 1); |
111 | | else |
112 | | mpn_add_n_sub_n (xp2, xm2, xp2, tp, n + 1); |
113 | | #else /* !HAVE_NATIVE_mpn_add_n_sub_n */ |
114 | 0 | if (neg) |
115 | 0 | mpn_sub_n (xm2, tp, xp2, n + 1); |
116 | 0 | else |
117 | 0 | mpn_sub_n (xm2, xp2, tp, n + 1); |
118 | |
|
119 | 0 | mpn_add_n (xp2, xp2, tp, n + 1); |
120 | 0 | #endif /* !HAVE_NATIVE_mpn_add_n_sub_n */ |
121 | |
|
122 | 0 | ASSERT (xp2[n] < (1<<(k+2))-1); |
123 | 0 | ASSERT (xm2[n] < ((1<<(k+3))-1 - (1^k&1))/3); |
124 | |
|
125 | 0 | neg ^= ((k & 1) - 1); |
126 | |
|
127 | 0 | return neg; |
128 | 0 | } |
129 | | |
130 | | #undef DO_addlsh2 |