| 1 | /* -*-c-*- |
| 2 | * |
| 3 | * Multiply many small numbers together |
| 4 | * |
| 5 | * (c) 2000 Straylight/Edgeware |
| 6 | */ |
| 7 | |
| 8 | /*----- Licensing notice --------------------------------------------------* |
| 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. |
| 16 | * |
| 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. |
| 21 | * |
| 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 | |
| 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 | |
| 62 | #define HWM (MPMUL_DEPTH - 20) |
| 63 | #define LWM (MPMUL_DEPTH / 2) |
| 64 | |
| 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) { |
| 82 | while (i > LWM || (i > 0 && MP_LEN(b->v[i - 1]) <= MP_LEN(x))) { |
| 83 | i--; |
| 84 | x = mp_mul(x, x, b->v[i]); |
| 85 | MP_DROP(b->v[i]); |
| 86 | } |
| 87 | } |
| 88 | |
| 89 | b->v[i++] = x; |
| 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 | } |
| 138 | mp_drop(x); |
| 139 | return (mpmul_done(&b)); |
| 140 | } |
| 141 | |
| 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; |
| 154 | if (!MP_EQ(fx, y)) { |
| 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 | { |
| 173 | test_run(argc, argv, tests, SRCDIR "/t/mp"); |
| 174 | return (0); |
| 175 | } |
| 176 | |
| 177 | #endif |
| 178 | |
| 179 | /*----- That's all, folks -------------------------------------------------*/ |