1 /*
2 Copyright (C) 2013 Fredrik Johansson
3
4 This file is part of Arb.
5
6 Arb is free software: you can redistribute it and/or modify it under
7 the terms of the GNU Lesser General Public License (LGPL) as published
8 by the Free Software Foundation; either version 2.1 of the License, or
9 (at your option) any later version. See <http://www.gnu.org/licenses/>.
10 */
11
12 #include "acb_poly.h"
13
14 void
_acb_poly_evaluate_rectangular(acb_t y,acb_srcptr poly,slong len,const acb_t x,slong prec)15 _acb_poly_evaluate_rectangular(acb_t y, acb_srcptr poly,
16 slong len, const acb_t x, slong prec)
17 {
18 slong i, m, r;
19 acb_ptr xs;
20 acb_t s, t, c;
21
22 if (len < 3)
23 {
24 if (len == 0)
25 {
26 acb_zero(y);
27 }
28 else if (len == 1)
29 {
30 acb_set_round(y, poly + 0, prec);
31 }
32 else if (len == 2)
33 {
34 acb_mul(y, x, poly + 1, prec);
35 acb_add(y, y, poly + 0, prec);
36 }
37 return;
38 }
39
40 m = n_sqrt(len) + 1;
41 r = (len + m - 1) / m;
42
43 xs = _acb_vec_init(m + 1);
44 acb_init(s);
45 acb_init(t);
46 acb_init(c);
47
48 _acb_vec_set_powers(xs, x, m + 1, prec);
49 acb_dot(y, poly + (r - 1) * m, 0, xs + 1, 1,
50 poly + (r - 1) * m + 1, 1, len - (r - 1) * m - 1, prec);
51
52 for (i = r - 2; i >= 0; i--)
53 {
54 acb_dot(s, poly + i * m, 0, xs + 1, 1,
55 poly + i * m + 1, 1, m - 1, prec);
56 acb_mul(y, y, xs + m, prec);
57 acb_add(y, y, s, prec);
58 }
59
60 _acb_vec_clear(xs, m + 1);
61 acb_clear(s);
62 acb_clear(t);
63 acb_clear(c);
64 }
65
66 void
acb_poly_evaluate_rectangular(acb_t res,const acb_poly_t f,const acb_t a,slong prec)67 acb_poly_evaluate_rectangular(acb_t res, const acb_poly_t f, const acb_t a, slong prec)
68 {
69 _acb_poly_evaluate_rectangular(res, f->coeffs, f->length, a, prec);
70 }
71
72