Commit | Line | Data |
---|---|---|
da38281c | 1 | /* -*-c-*- |
da38281c | 2 | * |
3 | * Multiply many small numbers together | |
4 | * | |
5 | * (c) 2000 Straylight/Edgeware | |
6 | */ | |
7 | ||
45c0fd36 | 8 | /*----- Licensing notice --------------------------------------------------* |
da38281c | 9 | * |
10 | * This file is part of Catacomb. | |
11 | * | |
12 | * Catacomb is free software; you can redistribute it and/or modify | |
13 | * it under the terms of the GNU Library General Public License as | |
14 | * published by the Free Software Foundation; either version 2 of the | |
15 | * License, or (at your option) any later version. | |
45c0fd36 | 16 | * |
da38281c | 17 | * Catacomb is distributed in the hope that it will be useful, |
18 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
19 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
20 | * GNU Library General Public License for more details. | |
45c0fd36 | 21 | * |
da38281c | 22 | * You should have received a copy of the GNU Library General Public |
23 | * License along with Catacomb; if not, write to the Free | |
24 | * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, | |
25 | * MA 02111-1307, USA. | |
26 | */ | |
27 | ||
da38281c | 28 | /*----- Header files ------------------------------------------------------*/ |
29 | ||
30 | #include "mp.h" | |
31 | #include "mpint.h" | |
32 | #include "mpmul.h" | |
33 | ||
34 | /*----- Main code ---------------------------------------------------------*/ | |
35 | ||
36 | /* --- @mpmul_init@ --- * | |
37 | * | |
38 | * Arguments: @mpmul *b@ = pointer to multiplier context to initialize | |
39 | * | |
40 | * Returns: --- | |
41 | * | |
42 | * Use: Initializes a big multiplier context for use. | |
43 | */ | |
44 | ||
45 | void mpmul_init(mpmul *b) | |
46 | { | |
47 | b->i = 0; | |
48 | } | |
49 | ||
50 | /* --- @mpmul_add@ --- * | |
51 | * | |
52 | * Arguments: @mpmul *b@ = pointer to multiplier context | |
53 | * @mp *x@ = the next factor to multiply in | |
54 | * | |
55 | * Returns: --- | |
56 | * | |
57 | * Use: Contributes another factor to the mix. It's important that | |
58 | * the integer lasts at least as long as the multiplication | |
59 | * context; this sort of rules out @mp_build@ integers. | |
60 | */ | |
61 | ||
ea932d59 MW |
62 | #define HWM (MPMUL_DEPTH - 20) |
63 | #define LWM (MPMUL_DEPTH / 2) | |
64 | ||
da38281c | 65 | void mpmul_add(mpmul *b, mp *x) |
66 | { | |
67 | size_t i = b->i; | |
68 | ||
69 | /* --- Now do the reduction step --- */ | |
70 | ||
71 | x = MP_COPY(x); | |
72 | ||
73 | while (i > 0) { | |
74 | if (MP_LEN(b->v[i - 1]) > MP_LEN(x)) | |
75 | break; | |
76 | i--; | |
77 | x = mp_mul(x, x, b->v[i]); | |
78 | MP_DROP(b->v[i]); | |
79 | } | |
80 | ||
81 | if (i > HWM) { | |
dfa4e2ce | 82 | while (i > LWM || (i > 0 && MP_LEN(b->v[i - 1]) <= MP_LEN(x))) { |
da38281c | 83 | i--; |
84 | x = mp_mul(x, x, b->v[i]); | |
85 | MP_DROP(b->v[i]); | |
86 | } | |
87 | } | |
88 | ||
dfa4e2ce | 89 | b->v[i++] = x; |
da38281c | 90 | b->i = i; |
91 | } | |
92 | ||
93 | /* --- @mpmul_done@ --- * | |
94 | * | |
95 | * Arguments: @mpmul *b@ = pointer to big multiplication context | |
96 | * | |
97 | * Returns: The product of all the numbers contributed. | |
98 | * | |
99 | * Use: Returns a (large) product of numbers. The context is | |
100 | * deallocated. | |
101 | */ | |
102 | ||
103 | mp *mpmul_done(mpmul *b) | |
104 | { | |
105 | size_t i = b->i; | |
106 | mp *x; | |
107 | ||
108 | if (!i) | |
109 | return (MP_ONE); | |
110 | i--; | |
111 | x = b->v[i]; | |
112 | while (i > 0) { | |
113 | i--; | |
114 | x = mp_mul(x, x, b->v[i]); | |
115 | MP_DROP(b->v[i]); | |
116 | } | |
117 | return (x); | |
118 | } | |
119 | ||
120 | /* --- @mp_factorial@ --- * | |
121 | * | |
122 | * Arguments: @unsigned long i@ = number whose factorial should be | |
123 | * computed. | |
124 | * | |
125 | * Returns: The requested factorial. | |
126 | */ | |
127 | ||
128 | mp *mp_factorial(unsigned long i) | |
129 | { | |
130 | unsigned long j; | |
131 | mp *x = MP_NEW; | |
132 | mpmul b = MPMUL_INIT; | |
133 | ||
134 | for (j = 1; j <= i; j++) { | |
135 | x = mp_fromulong(x, j); | |
136 | mpmul_add(&b, x); | |
137 | } | |
f1140c41 | 138 | mp_drop(x); |
da38281c | 139 | return (mpmul_done(&b)); |
140 | } | |
141 | ||
dfa4e2ce | 142 | /*----- Test rig ----------------------------------------------------------*/ |
143 | ||
144 | #ifdef TEST_RIG | |
145 | ||
146 | #include <mLib/testrig.h> | |
147 | ||
148 | static int vfact(dstr *v) | |
149 | { | |
150 | unsigned long x = *(unsigned long *)v[0].buf; | |
151 | mp *fx = *(mp **)v[1].buf; | |
152 | mp *y = mp_factorial(x); | |
153 | int ok = 1; | |
22bab86c | 154 | if (!MP_EQ(fx, y)) { |
dfa4e2ce | 155 | fprintf(stderr, "factorial failed\n"); |
156 | MP_FPRINTF(stderr, (stderr, "%lu! = ", x), fx); | |
157 | MP_EPRINT("result", y); | |
158 | ok = 0; | |
159 | } | |
160 | mp_drop(fx); | |
161 | mp_drop(y); | |
162 | assert(mparena_count(MPARENA_GLOBAL) == 0); | |
163 | return (ok); | |
164 | } | |
165 | ||
166 | static test_chunk tests[] = { | |
167 | { "factorial", vfact, { &type_ulong, &type_mp, 0 } }, | |
168 | { 0, 0, { 0 } } | |
169 | }; | |
170 | ||
171 | int main(int argc, char *argv[]) | |
172 | { | |
0f00dc4c | 173 | test_run(argc, argv, tests, SRCDIR "/t/mp"); |
dfa4e2ce | 174 | return (0); |
175 | } | |
176 | ||
177 | #endif | |
178 | ||
da38281c | 179 | /*----- That's all, folks -------------------------------------------------*/ |