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
|
/* See LICENSE file for copyright and license details. */
#include "internals.h"
void
zsqr(z_t a, z_t b)
{
/*
* Karatsuba algorithm, optimised for equal factors.
*/
size_t m2;
z_t z0, z1, z2, high, low;
int sign;
if (EXPECT(zzero(b), 0)) {
SET_SIGNUM(a, 0);
return;
}
m2 = zbits(b);
if (m2 <= BITS_PER_CHAR / 2) {
/* zsetu(a, b->chars[0] * b->chars[0]); { */
ENSURE_SIZE(a, 1);
a->used = 1;
a->chars[0] = b->chars[0] * b->chars[0];
/* } */
SET_SIGNUM(a, 1);
return;
}
sign = zsignum(b);
SET_SIGNUM(b, 1);
m2 >>= 1;
zinit(z0);
zinit(z1);
zinit(z2);
zinit(high);
zinit(low);
zsplit(high, low, b, m2);
#if 1
zsqr(z0, low);
zsqr(z2, high);
zmul(z1, low, high);
zlsh(z1, z1, m2 + 1);
m2 <<= 1;
zlsh(z2, z2, m2);
zadd(a, z2, z1);
zadd(a, a, z0);
#else
zsqr(z0, low);
zsqr(z2, high);
zmul(z1, low, low);
zlsh(z0, z0, m2 + 1);
zlsh(z1, z1, m2 + 1);
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(high);
zfree(low);
SET_SIGNUM(b, sign);
SET_SIGNUM(a, 1);
}
|
