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1 | /* -*-c-*- |
2 | * |
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3 | * $Id: mpmul.c,v 1.5 2004/04/08 01:36:15 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 | |
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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 | |
64 | void mpmul_add(mpmul *b, mp *x) |
65 | { |
66 | size_t i = b->i; |
67 | |
68 | /* --- Now do the reduction step --- */ |
69 | |
70 | x = MP_COPY(x); |
71 | |
72 | while (i > 0) { |
73 | if (MP_LEN(b->v[i - 1]) > MP_LEN(x)) |
74 | break; |
75 | i--; |
76 | x = mp_mul(x, x, b->v[i]); |
77 | MP_DROP(b->v[i]); |
78 | } |
79 | |
80 | if (i > HWM) { |
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81 | while (i > LWM || (i > 0 && MP_LEN(b->v[i - 1]) <= MP_LEN(x))) { |
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82 | i--; |
83 | x = mp_mul(x, x, b->v[i]); |
84 | MP_DROP(b->v[i]); |
85 | } |
86 | } |
87 | |
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88 | b->v[i++] = x; |
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89 | b->i = i; |
90 | } |
91 | |
92 | /* --- @mpmul_done@ --- * |
93 | * |
94 | * Arguments: @mpmul *b@ = pointer to big multiplication context |
95 | * |
96 | * Returns: The product of all the numbers contributed. |
97 | * |
98 | * Use: Returns a (large) product of numbers. The context is |
99 | * deallocated. |
100 | */ |
101 | |
102 | mp *mpmul_done(mpmul *b) |
103 | { |
104 | size_t i = b->i; |
105 | mp *x; |
106 | |
107 | if (!i) |
108 | return (MP_ONE); |
109 | i--; |
110 | x = b->v[i]; |
111 | while (i > 0) { |
112 | i--; |
113 | x = mp_mul(x, x, b->v[i]); |
114 | MP_DROP(b->v[i]); |
115 | } |
116 | return (x); |
117 | } |
118 | |
119 | /* --- @mp_factorial@ --- * |
120 | * |
121 | * Arguments: @unsigned long i@ = number whose factorial should be |
122 | * computed. |
123 | * |
124 | * Returns: The requested factorial. |
125 | */ |
126 | |
127 | mp *mp_factorial(unsigned long i) |
128 | { |
129 | unsigned long j; |
130 | mp *x = MP_NEW; |
131 | mpmul b = MPMUL_INIT; |
132 | |
133 | for (j = 1; j <= i; j++) { |
134 | x = mp_fromulong(x, j); |
135 | mpmul_add(&b, x); |
136 | } |
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137 | mp_drop(x); |
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138 | return (mpmul_done(&b)); |
139 | } |
140 | |
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141 | /*----- Test rig ----------------------------------------------------------*/ |
142 | |
143 | #ifdef TEST_RIG |
144 | |
145 | #include <mLib/testrig.h> |
146 | |
147 | static int vfact(dstr *v) |
148 | { |
149 | unsigned long x = *(unsigned long *)v[0].buf; |
150 | mp *fx = *(mp **)v[1].buf; |
151 | mp *y = mp_factorial(x); |
152 | int ok = 1; |
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153 | if (!MP_EQ(fx, y)) { |
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154 | fprintf(stderr, "factorial failed\n"); |
155 | MP_FPRINTF(stderr, (stderr, "%lu! = ", x), fx); |
156 | MP_EPRINT("result", y); |
157 | ok = 0; |
158 | } |
159 | mp_drop(fx); |
160 | mp_drop(y); |
161 | assert(mparena_count(MPARENA_GLOBAL) == 0); |
162 | return (ok); |
163 | } |
164 | |
165 | static test_chunk tests[] = { |
166 | { "factorial", vfact, { &type_ulong, &type_mp, 0 } }, |
167 | { 0, 0, { 0 } } |
168 | }; |
169 | |
170 | int main(int argc, char *argv[]) |
171 | { |
172 | test_run(argc, argv, tests, SRCDIR "/tests/mp"); |
173 | return (0); |
174 | } |
175 | |
176 | #endif |
177 | |
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178 | /*----- That's all, folks -------------------------------------------------*/ |