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1 | /* -*-c-*- |
2 | * |
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3 | * $Id: mpmul.c,v 1.4 2001/02/03 12:00:29 mdw Exp $ |
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4 | * |
5 | * Multiply many small numbers together |
6 | * |
7 | * (c) 2000 Straylight/Edgeware |
8 | */ |
9 | |
10 | /*----- Licensing notice --------------------------------------------------* |
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. |
18 | * |
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. |
23 | * |
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 | |
30 | /*----- Revision history --------------------------------------------------* |
31 | * |
32 | * $Log: mpmul.c,v $ |
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33 | * Revision 1.4 2001/02/03 12:00:29 mdw |
34 | * Now @mp_drop@ checks its argument is non-NULL before attempting to free |
35 | * it. Note that the macro version @MP_DROP@ doesn't do this. |
36 | * |
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37 | * Revision 1.3 2000/10/08 12:11:22 mdw |
38 | * Use @MP_EQ@ instead of @MP_CMP@. |
39 | * |
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40 | * Revision 1.2 2000/07/09 21:31:10 mdw |
41 | * Fix bug, and add a test rig. |
42 | * |
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43 | * Revision 1.1 2000/07/01 11:21:39 mdw |
44 | * New interface for computing products of many (small) integers. |
45 | * |
46 | */ |
47 | |
48 | /*----- Header files ------------------------------------------------------*/ |
49 | |
50 | #include "mp.h" |
51 | #include "mpint.h" |
52 | #include "mpmul.h" |
53 | |
54 | /*----- Main code ---------------------------------------------------------*/ |
55 | |
56 | /* --- @mpmul_init@ --- * |
57 | * |
58 | * Arguments: @mpmul *b@ = pointer to multiplier context to initialize |
59 | * |
60 | * Returns: --- |
61 | * |
62 | * Use: Initializes a big multiplier context for use. |
63 | */ |
64 | |
65 | void mpmul_init(mpmul *b) |
66 | { |
67 | b->i = 0; |
68 | } |
69 | |
70 | /* --- @mpmul_add@ --- * |
71 | * |
72 | * Arguments: @mpmul *b@ = pointer to multiplier context |
73 | * @mp *x@ = the next factor to multiply in |
74 | * |
75 | * Returns: --- |
76 | * |
77 | * Use: Contributes another factor to the mix. It's important that |
78 | * the integer lasts at least as long as the multiplication |
79 | * context; this sort of rules out @mp_build@ integers. |
80 | */ |
81 | |
82 | void mpmul_add(mpmul *b, mp *x) |
83 | { |
84 | size_t i = b->i; |
85 | |
86 | /* --- Now do the reduction step --- */ |
87 | |
88 | x = MP_COPY(x); |
89 | |
90 | while (i > 0) { |
91 | if (MP_LEN(b->v[i - 1]) > MP_LEN(x)) |
92 | break; |
93 | i--; |
94 | x = mp_mul(x, x, b->v[i]); |
95 | MP_DROP(b->v[i]); |
96 | } |
97 | |
98 | if (i > HWM) { |
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99 | while (i > LWM || (i > 0 && MP_LEN(b->v[i - 1]) <= MP_LEN(x))) { |
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100 | i--; |
101 | x = mp_mul(x, x, b->v[i]); |
102 | MP_DROP(b->v[i]); |
103 | } |
104 | } |
105 | |
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106 | b->v[i++] = x; |
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107 | b->i = i; |
108 | } |
109 | |
110 | /* --- @mpmul_done@ --- * |
111 | * |
112 | * Arguments: @mpmul *b@ = pointer to big multiplication context |
113 | * |
114 | * Returns: The product of all the numbers contributed. |
115 | * |
116 | * Use: Returns a (large) product of numbers. The context is |
117 | * deallocated. |
118 | */ |
119 | |
120 | mp *mpmul_done(mpmul *b) |
121 | { |
122 | size_t i = b->i; |
123 | mp *x; |
124 | |
125 | if (!i) |
126 | return (MP_ONE); |
127 | i--; |
128 | x = b->v[i]; |
129 | while (i > 0) { |
130 | i--; |
131 | x = mp_mul(x, x, b->v[i]); |
132 | MP_DROP(b->v[i]); |
133 | } |
134 | return (x); |
135 | } |
136 | |
137 | /* --- @mp_factorial@ --- * |
138 | * |
139 | * Arguments: @unsigned long i@ = number whose factorial should be |
140 | * computed. |
141 | * |
142 | * Returns: The requested factorial. |
143 | */ |
144 | |
145 | mp *mp_factorial(unsigned long i) |
146 | { |
147 | unsigned long j; |
148 | mp *x = MP_NEW; |
149 | mpmul b = MPMUL_INIT; |
150 | |
151 | for (j = 1; j <= i; j++) { |
152 | x = mp_fromulong(x, j); |
153 | mpmul_add(&b, x); |
154 | } |
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155 | mp_drop(x); |
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156 | return (mpmul_done(&b)); |
157 | } |
158 | |
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159 | /*----- Test rig ----------------------------------------------------------*/ |
160 | |
161 | #ifdef TEST_RIG |
162 | |
163 | #include <mLib/testrig.h> |
164 | |
165 | static int vfact(dstr *v) |
166 | { |
167 | unsigned long x = *(unsigned long *)v[0].buf; |
168 | mp *fx = *(mp **)v[1].buf; |
169 | mp *y = mp_factorial(x); |
170 | int ok = 1; |
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171 | if (!MP_EQ(fx, y)) { |
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172 | fprintf(stderr, "factorial failed\n"); |
173 | MP_FPRINTF(stderr, (stderr, "%lu! = ", x), fx); |
174 | MP_EPRINT("result", y); |
175 | ok = 0; |
176 | } |
177 | mp_drop(fx); |
178 | mp_drop(y); |
179 | assert(mparena_count(MPARENA_GLOBAL) == 0); |
180 | return (ok); |
181 | } |
182 | |
183 | static test_chunk tests[] = { |
184 | { "factorial", vfact, { &type_ulong, &type_mp, 0 } }, |
185 | { 0, 0, { 0 } } |
186 | }; |
187 | |
188 | int main(int argc, char *argv[]) |
189 | { |
190 | test_run(argc, argv, tests, SRCDIR "/tests/mp"); |
191 | return (0); |
192 | } |
193 | |
194 | #endif |
195 | |
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196 | /*----- That's all, folks -------------------------------------------------*/ |