1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
|
/* See LICENSE file for copyright and license details. */
#include "internals.h"
void
zmul(z_t a, z_t b, z_t c)
{
/*
* Karatsuba algorithm
*/
size_t m, m2;
z_t z0, z1, z2, b_high, b_low, c_high, c_low;
int b_sign, c_sign;
if (zzero(b) || zzero(c)) {
SET_SIGNUM(a, 0);
return;
}
m = zbits(b);
m2 = b == c ? m : zbits(c);
b_sign = zsignum(b);
c_sign = zsignum(c);
if (m <= 16 && m2 <= 16) {
zsetu(a, b->chars[0] * c->chars[0]);
SET_SIGNUM(a, b_sign * c_sign);
return;
}
SET_SIGNUM(b, 1);
SET_SIGNUM(c, 1);
m = MAX(m, m2);
m2 = m >> 1;
zinit(z0);
zinit(z1);
zinit(z2);
zinit(b_high);
zinit(b_low);
zinit(c_high);
zinit(c_low);
zsplit(b_high, b_low, b, m2);
zsplit(c_high, c_low, c, m2);
#if 0
zmul(z0, b_low, c_low);
zmul(z2, b_high, c_high);
zadd(b_low, b_low, b_high);
zadd(c_low, c_low, c_high);
zmul(z1, b_low, c_low);
zsub(z1, z1, z0);
zsub(z1, z1, z2);
zlsh(z2, z2, m2);
m2 <<= 1;
zlsh(z1, z1, m2);
zadd(a, z2, z1);
zadd(a, a, z0);
#else
zmul(z0, b_low, c_low);
zmul(z2, b_high, c_high);
zsub(b_low, b_high, b_low);
zsub(c_low, c_high, c_low);
zmul(z1, b_low, c_low);
zlsh(z0, z0, m2 + 1);
zlsh(z1, z1, m2);
zlsh(a, z2, m2);
m2 <<= 1;
zlsh(z2, z2, m2);
zadd(z2, z2, a);
zsub(a, z2, z1);
zadd(a, a, z0);
#endif
zfree(z0);
zfree(z1);
zfree(z2);
zfree(b_high);
zfree(b_low);
zfree(c_high);
zfree(c_low);
SET_SIGNUM(b, b_sign);
SET_SIGNUM(c, c_sign);
SET_SIGNUM(a, b_sign * c_sign);
}
|
