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
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
|
#include <tommath.h>
#ifdef BN_MP_TOOM_SQR_C
/* LibTomMath, multiple-precision integer library -- Tom St Denis
*
* LibTomMath is a library that provides multiple-precision
* integer arithmetic as well as number theoretic functionality.
*
* The library was designed directly after the MPI library by
* Michael Fromberger but has been written from scratch with
* additional optimizations in place.
*
* The library is free for all purposes without any express
* guarantee it works.
*
* Tom St Denis, tomstdenis@gmail.com, http://libtom.org
*/
/* squaring using Toom-Cook 3-way algorithm */
int
mp_toom_sqr(mp_int *a, mp_int *b)
{
mp_int w0, w1, w2, w3, w4, tmp1, a0, a1, a2;
int res, B;
/* init temps */
if ((res = mp_init_multi(&w0, &w1, &w2, &w3, &w4, &a0, &a1, &a2, &tmp1, NULL)) != MP_OKAY) {
return res;
}
/* B */
B = a->used / 3;
/* a = a2 * B**2 + a1 * B + a0 */
if ((res = mp_mod_2d(a, DIGIT_BIT * B, &a0)) != MP_OKAY) {
goto ERR;
}
if ((res = mp_copy(a, &a1)) != MP_OKAY) {
goto ERR;
}
mp_rshd(&a1, B);
mp_mod_2d(&a1, DIGIT_BIT * B, &a1);
if ((res = mp_copy(a, &a2)) != MP_OKAY) {
goto ERR;
}
mp_rshd(&a2, B*2);
/* w0 = a0*a0 */
if ((res = mp_sqr(&a0, &w0)) != MP_OKAY) {
goto ERR;
}
/* w4 = a2 * a2 */
if ((res = mp_sqr(&a2, &w4)) != MP_OKAY) {
goto ERR;
}
/* w1 = (a2 + 2(a1 + 2a0))**2 */
if ((res = mp_mul_2(&a0, &tmp1)) != MP_OKAY) {
goto ERR;
}
if ((res = mp_add(&tmp1, &a1, &tmp1)) != MP_OKAY) {
goto ERR;
}
if ((res = mp_mul_2(&tmp1, &tmp1)) != MP_OKAY) {
goto ERR;
}
if ((res = mp_add(&tmp1, &a2, &tmp1)) != MP_OKAY) {
goto ERR;
}
if ((res = mp_sqr(&tmp1, &w1)) != MP_OKAY) {
goto ERR;
}
/* w3 = (a0 + 2(a1 + 2a2))**2 */
if ((res = mp_mul_2(&a2, &tmp1)) != MP_OKAY) {
goto ERR;
}
if ((res = mp_add(&tmp1, &a1, &tmp1)) != MP_OKAY) {
goto ERR;
}
if ((res = mp_mul_2(&tmp1, &tmp1)) != MP_OKAY) {
goto ERR;
}
if ((res = mp_add(&tmp1, &a0, &tmp1)) != MP_OKAY) {
goto ERR;
}
if ((res = mp_sqr(&tmp1, &w3)) != MP_OKAY) {
goto ERR;
}
/* w2 = (a2 + a1 + a0)**2 */
if ((res = mp_add(&a2, &a1, &tmp1)) != MP_OKAY) {
goto ERR;
}
if ((res = mp_add(&tmp1, &a0, &tmp1)) != MP_OKAY) {
goto ERR;
}
if ((res = mp_sqr(&tmp1, &w2)) != MP_OKAY) {
goto ERR;
}
/* now solve the matrix
0 0 0 0 1
1 2 4 8 16
1 1 1 1 1
16 8 4 2 1
1 0 0 0 0
using 12 subtractions, 4 shifts, 2 small divisions and 1 small multiplication.
*/
/* r1 - r4 */
if ((res = mp_sub(&w1, &w4, &w1)) != MP_OKAY) {
goto ERR;
}
/* r3 - r0 */
if ((res = mp_sub(&w3, &w0, &w3)) != MP_OKAY) {
goto ERR;
}
/* r1/2 */
if ((res = mp_div_2(&w1, &w1)) != MP_OKAY) {
goto ERR;
}
/* r3/2 */
if ((res = mp_div_2(&w3, &w3)) != MP_OKAY) {
goto ERR;
}
/* r2 - r0 - r4 */
if ((res = mp_sub(&w2, &w0, &w2)) != MP_OKAY) {
goto ERR;
}
if ((res = mp_sub(&w2, &w4, &w2)) != MP_OKAY) {
goto ERR;
}
/* r1 - r2 */
if ((res = mp_sub(&w1, &w2, &w1)) != MP_OKAY) {
goto ERR;
}
/* r3 - r2 */
if ((res = mp_sub(&w3, &w2, &w3)) != MP_OKAY) {
goto ERR;
}
/* r1 - 8r0 */
if ((res = mp_mul_2d(&w0, 3, &tmp1)) != MP_OKAY) {
goto ERR;
}
if ((res = mp_sub(&w1, &tmp1, &w1)) != MP_OKAY) {
goto ERR;
}
/* r3 - 8r4 */
if ((res = mp_mul_2d(&w4, 3, &tmp1)) != MP_OKAY) {
goto ERR;
}
if ((res = mp_sub(&w3, &tmp1, &w3)) != MP_OKAY) {
goto ERR;
}
/* 3r2 - r1 - r3 */
if ((res = mp_mul_d(&w2, 3, &w2)) != MP_OKAY) {
goto ERR;
}
if ((res = mp_sub(&w2, &w1, &w2)) != MP_OKAY) {
goto ERR;
}
if ((res = mp_sub(&w2, &w3, &w2)) != MP_OKAY) {
goto ERR;
}
/* r1 - r2 */
if ((res = mp_sub(&w1, &w2, &w1)) != MP_OKAY) {
goto ERR;
}
/* r3 - r2 */
if ((res = mp_sub(&w3, &w2, &w3)) != MP_OKAY) {
goto ERR;
}
/* r1/3 */
if ((res = mp_div_3(&w1, &w1, NULL)) != MP_OKAY) {
goto ERR;
}
/* r3/3 */
if ((res = mp_div_3(&w3, &w3, NULL)) != MP_OKAY) {
goto ERR;
}
/* at this point shift W[n] by B*n */
if ((res = mp_lshd(&w1, 1*B)) != MP_OKAY) {
goto ERR;
}
if ((res = mp_lshd(&w2, 2*B)) != MP_OKAY) {
goto ERR;
}
if ((res = mp_lshd(&w3, 3*B)) != MP_OKAY) {
goto ERR;
}
if ((res = mp_lshd(&w4, 4*B)) != MP_OKAY) {
goto ERR;
}
if ((res = mp_add(&w0, &w1, b)) != MP_OKAY) {
goto ERR;
}
if ((res = mp_add(&w2, &w3, &tmp1)) != MP_OKAY) {
goto ERR;
}
if ((res = mp_add(&w4, &tmp1, &tmp1)) != MP_OKAY) {
goto ERR;
}
if ((res = mp_add(&tmp1, b, b)) != MP_OKAY) {
goto ERR;
}
ERR:
mp_clear_multi(&w0, &w1, &w2, &w3, &w4, &a0, &a1, &a2, &tmp1, NULL);
return res;
}
#endif
/* $Source: /cvs/libtom/libtommath/bn_mp_toom_sqr.c,v $ */
/* $Revision: 1.4 $ */
/* $Date: 2006/12/28 01:25:13 $ */
|
