1 /*
2 Copyright (C) 2012 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
_acb_poly_tree_alloc(slong len)14 acb_ptr * _acb_poly_tree_alloc(slong len)
15 {
16 acb_ptr * tree = NULL;
17
18 if (len)
19 {
20 slong i, height = FLINT_CLOG2(len);
21
22 tree = flint_malloc(sizeof(acb_ptr) * (height + 1));
23 for (i = 0; i <= height; i++)
24 tree[i] = _acb_vec_init(len + (len >> i) + 1);
25 }
26
27 return tree;
28 }
29
_acb_poly_tree_free(acb_ptr * tree,slong len)30 void _acb_poly_tree_free(acb_ptr * tree, slong len)
31 {
32 if (len)
33 {
34 slong i, height = FLINT_CLOG2(len);
35
36 for (i = 0; i <= height; i++)
37 _acb_vec_clear(tree[i], len + (len >> i) + 1);
38
39 flint_free(tree);
40 }
41 }
42
43 void
_acb_poly_tree_build(acb_ptr * tree,acb_srcptr roots,slong len,slong prec)44 _acb_poly_tree_build(acb_ptr * tree, acb_srcptr roots, slong len, slong prec)
45 {
46 slong height, pow, left, i;
47 acb_ptr pa, pb;
48 acb_srcptr a, b;
49
50 if (len == 0)
51 return;
52
53 height = FLINT_CLOG2(len);
54
55 /* zeroth level, (x-a) */
56 for (i = 0; i < len; i++)
57 {
58 acb_one(tree[0] + (2 * i + 1));
59 acb_neg(tree[0] + (2 * i), roots + i);
60 }
61
62 /* first level, (x-a)(x-b) = x^2 + (-a-b)*x + a*b */
63 if (height > 1)
64 {
65 pa = tree[1];
66
67 for (i = 0; i < len / 2; i++)
68 {
69 a = (acb_srcptr) (roots + (2 * i));
70 b = (acb_srcptr) (roots + (2 * i + 1));
71
72 acb_mul(pa + (3 * i), a, b, prec);
73 acb_add(pa + (3 * i + 1), a, b, prec);
74 acb_neg(pa + (3 * i + 1), pa + (3 * i + 1));
75 acb_one(pa + (3 * i + 2));
76 }
77
78 if (len & 1)
79 {
80 acb_neg(pa + (3 * (len / 2)), roots + len - 1);
81 acb_one(pa + (3 * (len / 2) + 1));
82 }
83 }
84
85 for (i = 1; i < height - 1; i++)
86 {
87 left = len;
88 pow = WORD(1) << i;
89 pa = tree[i];
90 pb = tree[i + 1];
91
92 while (left >= 2 * pow)
93 {
94 _acb_poly_mul_monic(pb, pa, pow + 1, pa + pow + 1, pow + 1, prec);
95 left -= 2 * pow;
96 pa += 2 * pow + 2;
97 pb += 2 * pow + 1;
98 }
99
100 if (left > pow)
101 {
102 _acb_poly_mul_monic(pb, pa, pow + 1, pa + pow + 1, left - pow + 1, prec);
103 }
104 else if (left > 0)
105 _acb_vec_set(pb, pa, left + 1);
106 }
107 }
108