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da38281c | 1 | /* -*-c-*- |
2 | * | |
b817bfc6 | 3 | * $Id: mpmul.c,v 1.5 2004/04/08 01:36:15 mdw Exp $ |
da38281c | 4 | * |
5 | * Multiply many small numbers together | |
6 | * | |
7 | * (c) 2000 Straylight/Edgeware | |
8 | */ | |
9 | ||
45c0fd36 | 10 | /*----- Licensing notice --------------------------------------------------* |
da38281c | 11 | * |
12 | * This file is part of Catacomb. | |
13 | * | |
14 | * Catacomb is free software; you can redistribute it and/or modify | |
15 | * it under the terms of the GNU Library General Public License as | |
16 | * published by the Free Software Foundation; either version 2 of the | |
17 | * License, or (at your option) any later version. | |
45c0fd36 | 18 | * |
da38281c | 19 | * Catacomb is distributed in the hope that it will be useful, |
20 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
21 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
22 | * GNU Library General Public License for more details. | |
45c0fd36 | 23 | * |
da38281c | 24 | * You should have received a copy of the GNU Library General Public |
25 | * License along with Catacomb; if not, write to the Free | |
26 | * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, | |
27 | * MA 02111-1307, USA. | |
28 | */ | |
29 | ||
da38281c | 30 | /*----- Header files ------------------------------------------------------*/ |
31 | ||
32 | #include "mp.h" | |
33 | #include "mpint.h" | |
34 | #include "mpmul.h" | |
35 | ||
36 | /*----- Main code ---------------------------------------------------------*/ | |
37 | ||
38 | /* --- @mpmul_init@ --- * | |
39 | * | |
40 | * Arguments: @mpmul *b@ = pointer to multiplier context to initialize | |
41 | * | |
42 | * Returns: --- | |
43 | * | |
44 | * Use: Initializes a big multiplier context for use. | |
45 | */ | |
46 | ||
47 | void mpmul_init(mpmul *b) | |
48 | { | |
49 | b->i = 0; | |
50 | } | |
51 | ||
52 | /* --- @mpmul_add@ --- * | |
53 | * | |
54 | * Arguments: @mpmul *b@ = pointer to multiplier context | |
55 | * @mp *x@ = the next factor to multiply in | |
56 | * | |
57 | * Returns: --- | |
58 | * | |
59 | * Use: Contributes another factor to the mix. It's important that | |
60 | * the integer lasts at least as long as the multiplication | |
61 | * context; this sort of rules out @mp_build@ integers. | |
62 | */ | |
63 | ||
ea932d59 MW |
64 | #define HWM (MPMUL_DEPTH - 20) |
65 | #define LWM (MPMUL_DEPTH / 2) | |
66 | ||
da38281c | 67 | void mpmul_add(mpmul *b, mp *x) |
68 | { | |
69 | size_t i = b->i; | |
70 | ||
71 | /* --- Now do the reduction step --- */ | |
72 | ||
73 | x = MP_COPY(x); | |
74 | ||
75 | while (i > 0) { | |
76 | if (MP_LEN(b->v[i - 1]) > MP_LEN(x)) | |
77 | break; | |
78 | i--; | |
79 | x = mp_mul(x, x, b->v[i]); | |
80 | MP_DROP(b->v[i]); | |
81 | } | |
82 | ||
83 | if (i > HWM) { | |
dfa4e2ce | 84 | while (i > LWM || (i > 0 && MP_LEN(b->v[i - 1]) <= MP_LEN(x))) { |
da38281c | 85 | i--; |
86 | x = mp_mul(x, x, b->v[i]); | |
87 | MP_DROP(b->v[i]); | |
88 | } | |
89 | } | |
90 | ||
dfa4e2ce | 91 | b->v[i++] = x; |
da38281c | 92 | b->i = i; |
93 | } | |
94 | ||
95 | /* --- @mpmul_done@ --- * | |
96 | * | |
97 | * Arguments: @mpmul *b@ = pointer to big multiplication context | |
98 | * | |
99 | * Returns: The product of all the numbers contributed. | |
100 | * | |
101 | * Use: Returns a (large) product of numbers. The context is | |
102 | * deallocated. | |
103 | */ | |
104 | ||
105 | mp *mpmul_done(mpmul *b) | |
106 | { | |
107 | size_t i = b->i; | |
108 | mp *x; | |
109 | ||
110 | if (!i) | |
111 | return (MP_ONE); | |
112 | i--; | |
113 | x = b->v[i]; | |
114 | while (i > 0) { | |
115 | i--; | |
116 | x = mp_mul(x, x, b->v[i]); | |
117 | MP_DROP(b->v[i]); | |
118 | } | |
119 | return (x); | |
120 | } | |
121 | ||
122 | /* --- @mp_factorial@ --- * | |
123 | * | |
124 | * Arguments: @unsigned long i@ = number whose factorial should be | |
125 | * computed. | |
126 | * | |
127 | * Returns: The requested factorial. | |
128 | */ | |
129 | ||
130 | mp *mp_factorial(unsigned long i) | |
131 | { | |
132 | unsigned long j; | |
133 | mp *x = MP_NEW; | |
134 | mpmul b = MPMUL_INIT; | |
135 | ||
136 | for (j = 1; j <= i; j++) { | |
137 | x = mp_fromulong(x, j); | |
138 | mpmul_add(&b, x); | |
139 | } | |
f1140c41 | 140 | mp_drop(x); |
da38281c | 141 | return (mpmul_done(&b)); |
142 | } | |
143 | ||
dfa4e2ce | 144 | /*----- Test rig ----------------------------------------------------------*/ |
145 | ||
146 | #ifdef TEST_RIG | |
147 | ||
148 | #include <mLib/testrig.h> | |
149 | ||
150 | static int vfact(dstr *v) | |
151 | { | |
152 | unsigned long x = *(unsigned long *)v[0].buf; | |
153 | mp *fx = *(mp **)v[1].buf; | |
154 | mp *y = mp_factorial(x); | |
155 | int ok = 1; | |
22bab86c | 156 | if (!MP_EQ(fx, y)) { |
dfa4e2ce | 157 | fprintf(stderr, "factorial failed\n"); |
158 | MP_FPRINTF(stderr, (stderr, "%lu! = ", x), fx); | |
159 | MP_EPRINT("result", y); | |
160 | ok = 0; | |
161 | } | |
162 | mp_drop(fx); | |
163 | mp_drop(y); | |
164 | assert(mparena_count(MPARENA_GLOBAL) == 0); | |
165 | return (ok); | |
166 | } | |
167 | ||
168 | static test_chunk tests[] = { | |
169 | { "factorial", vfact, { &type_ulong, &type_mp, 0 } }, | |
170 | { 0, 0, { 0 } } | |
171 | }; | |
172 | ||
173 | int main(int argc, char *argv[]) | |
174 | { | |
175 | test_run(argc, argv, tests, SRCDIR "/tests/mp"); | |
176 | return (0); | |
177 | } | |
178 | ||
179 | #endif | |
180 | ||
da38281c | 181 | /*----- That's all, folks -------------------------------------------------*/ |