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annotate libiberty/random.c @ 158:494b0b89df80 default tip
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| author | Shinji KONO <kono@ie.u-ryukyu.ac.jp> |
|---|---|
| date | Mon, 25 May 2020 18:13:55 +0900 |
| parents | f6334be47118 |
| children |
| rev | line source |
|---|---|
| 0 | 1 /* |
| 2 * Copyright (c) 1983 Regents of the University of California. | |
| 3 * All rights reserved. | |
| 4 * | |
| 5 * Redistribution and use in source and binary forms, with or without | |
| 6 * modification, are permitted provided that the following conditions | |
| 7 * are met: | |
| 8 * 1. Redistributions of source code must retain the above copyright | |
| 9 * notice, this list of conditions and the following disclaimer. | |
| 10 * 2. Redistributions in binary form must reproduce the above copyright | |
| 11 * notice, this list of conditions and the following disclaimer in the | |
| 12 * documentation and/or other materials provided with the distribution. | |
| 13 * 3. [rescinded 22 July 1999] | |
| 14 * 4. Neither the name of the University nor the names of its contributors | |
| 15 * may be used to endorse or promote products derived from this software | |
| 16 * without specific prior written permission. | |
| 17 * | |
| 18 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND | |
| 19 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE | |
| 20 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE | |
| 21 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE | |
| 22 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL | |
| 23 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS | |
| 24 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) | |
| 25 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT | |
| 26 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY | |
| 27 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF | |
| 28 * SUCH DAMAGE. | |
| 29 */ | |
| 30 | |
| 31 /* | |
| 32 * This is derived from the Berkeley source: | |
| 33 * @(#)random.c 5.5 (Berkeley) 7/6/88 | |
| 34 * It was reworked for the GNU C Library by Roland McGrath. | |
| 35 */ | |
| 36 | |
| 37 /* | |
| 38 | |
| 39 @deftypefn Supplement {long int} random (void) | |
| 40 @deftypefnx Supplement void srandom (unsigned int @var{seed}) | |
|
67
f6334be47118
update gcc from gcc-4.6-20100522 to gcc-4.6-20110318
nobuyasu <dimolto@cr.ie.u-ryukyu.ac.jp>
parents:
0
diff
changeset
|
41 @deftypefnx Supplement void* initstate (unsigned int @var{seed}, @ |
|
f6334be47118
update gcc from gcc-4.6-20100522 to gcc-4.6-20110318
nobuyasu <dimolto@cr.ie.u-ryukyu.ac.jp>
parents:
0
diff
changeset
|
42 void *@var{arg_state}, unsigned long @var{n}) |
| 0 | 43 @deftypefnx Supplement void* setstate (void *@var{arg_state}) |
| 44 | |
| 45 Random number functions. @code{random} returns a random number in the | |
| 46 range 0 to @code{LONG_MAX}. @code{srandom} initializes the random | |
| 47 number generator to some starting point determined by @var{seed} | |
| 48 (else, the values returned by @code{random} are always the same for each | |
| 49 run of the program). @code{initstate} and @code{setstate} allow fine-grained | |
| 50 control over the state of the random number generator. | |
| 51 | |
| 52 @end deftypefn | |
| 53 | |
| 54 */ | |
| 55 | |
| 56 #include <errno.h> | |
| 57 | |
| 58 #if 0 | |
| 59 | |
| 60 #include <ansidecl.h> | |
| 61 #include <limits.h> | |
| 62 #include <stddef.h> | |
| 63 #include <stdlib.h> | |
| 64 | |
| 65 #else | |
| 66 | |
| 67 #define ULONG_MAX ((unsigned long)(~0L)) /* 0xFFFFFFFF for 32-bits */ | |
| 68 #define LONG_MAX ((long)(ULONG_MAX >> 1)) /* 0x7FFFFFFF for 32-bits*/ | |
| 69 | |
| 70 #ifdef __STDC__ | |
| 71 # define PTR void * | |
| 72 # ifndef NULL | |
| 73 # define NULL (void *) 0 | |
| 74 # endif | |
| 75 #else | |
| 76 # define PTR char * | |
| 77 # ifndef NULL | |
| 78 # define NULL (void *) 0 | |
| 79 # endif | |
| 80 #endif | |
| 81 | |
| 82 #endif | |
| 83 | |
| 84 long int random (void); | |
| 85 | |
| 86 /* An improved random number generation package. In addition to the standard | |
| 87 rand()/srand() like interface, this package also has a special state info | |
| 88 interface. The initstate() routine is called with a seed, an array of | |
| 89 bytes, and a count of how many bytes are being passed in; this array is | |
| 90 then initialized to contain information for random number generation with | |
| 91 that much state information. Good sizes for the amount of state | |
| 92 information are 32, 64, 128, and 256 bytes. The state can be switched by | |
| 93 calling the setstate() function with the same array as was initiallized | |
| 94 with initstate(). By default, the package runs with 128 bytes of state | |
| 95 information and generates far better random numbers than a linear | |
| 96 congruential generator. If the amount of state information is less than | |
| 97 32 bytes, a simple linear congruential R.N.G. is used. Internally, the | |
| 98 state information is treated as an array of longs; the zeroeth element of | |
| 99 the array is the type of R.N.G. being used (small integer); the remainder | |
| 100 of the array is the state information for the R.N.G. Thus, 32 bytes of | |
| 101 state information will give 7 longs worth of state information, which will | |
| 102 allow a degree seven polynomial. (Note: The zeroeth word of state | |
| 103 information also has some other information stored in it; see setstate | |
| 104 for details). The random number generation technique is a linear feedback | |
| 105 shift register approach, employing trinomials (since there are fewer terms | |
| 106 to sum up that way). In this approach, the least significant bit of all | |
| 107 the numbers in the state table will act as a linear feedback shift register, | |
| 108 and will have period 2^deg - 1 (where deg is the degree of the polynomial | |
| 109 being used, assuming that the polynomial is irreducible and primitive). | |
| 110 The higher order bits will have longer periods, since their values are | |
| 111 also influenced by pseudo-random carries out of the lower bits. The | |
| 112 total period of the generator is approximately deg*(2**deg - 1); thus | |
| 113 doubling the amount of state information has a vast influence on the | |
| 114 period of the generator. Note: The deg*(2**deg - 1) is an approximation | |
| 115 only good for large deg, when the period of the shift register is the | |
| 116 dominant factor. With deg equal to seven, the period is actually much | |
| 117 longer than the 7*(2**7 - 1) predicted by this formula. */ | |
| 118 | |
| 119 | |
| 120 | |
| 121 /* For each of the currently supported random number generators, we have a | |
| 122 break value on the amount of state information (you need at least thi | |
| 123 bytes of state info to support this random number generator), a degree for | |
| 124 the polynomial (actually a trinomial) that the R.N.G. is based on, and | |
| 125 separation between the two lower order coefficients of the trinomial. */ | |
| 126 | |
| 127 /* Linear congruential. */ | |
| 128 #define TYPE_0 0 | |
| 129 #define BREAK_0 8 | |
| 130 #define DEG_0 0 | |
| 131 #define SEP_0 0 | |
| 132 | |
| 133 /* x**7 + x**3 + 1. */ | |
| 134 #define TYPE_1 1 | |
| 135 #define BREAK_1 32 | |
| 136 #define DEG_1 7 | |
| 137 #define SEP_1 3 | |
| 138 | |
| 139 /* x**15 + x + 1. */ | |
| 140 #define TYPE_2 2 | |
| 141 #define BREAK_2 64 | |
| 142 #define DEG_2 15 | |
| 143 #define SEP_2 1 | |
| 144 | |
| 145 /* x**31 + x**3 + 1. */ | |
| 146 #define TYPE_3 3 | |
| 147 #define BREAK_3 128 | |
| 148 #define DEG_3 31 | |
| 149 #define SEP_3 3 | |
| 150 | |
| 151 /* x**63 + x + 1. */ | |
| 152 #define TYPE_4 4 | |
| 153 #define BREAK_4 256 | |
| 154 #define DEG_4 63 | |
| 155 #define SEP_4 1 | |
| 156 | |
| 157 | |
| 158 /* Array versions of the above information to make code run faster. | |
| 159 Relies on fact that TYPE_i == i. */ | |
| 160 | |
| 161 #define MAX_TYPES 5 /* Max number of types above. */ | |
| 162 | |
| 163 static int degrees[MAX_TYPES] = { DEG_0, DEG_1, DEG_2, DEG_3, DEG_4 }; | |
| 164 static int seps[MAX_TYPES] = { SEP_0, SEP_1, SEP_2, SEP_3, SEP_4 }; | |
| 165 | |
| 166 | |
| 167 | |
| 168 /* Initially, everything is set up as if from: | |
| 169 initstate(1, randtbl, 128); | |
| 170 Note that this initialization takes advantage of the fact that srandom | |
| 171 advances the front and rear pointers 10*rand_deg times, and hence the | |
| 172 rear pointer which starts at 0 will also end up at zero; thus the zeroeth | |
| 173 element of the state information, which contains info about the current | |
| 174 position of the rear pointer is just | |
| 175 (MAX_TYPES * (rptr - state)) + TYPE_3 == TYPE_3. */ | |
| 176 | |
| 177 static long int randtbl[DEG_3 + 1] = | |
| 178 { TYPE_3, | |
| 179 0x9a319039, 0x32d9c024, 0x9b663182, 0x5da1f342, | |
| 180 0xde3b81e0, 0xdf0a6fb5, 0xf103bc02, 0x48f340fb, | |
| 181 0x7449e56b, 0xbeb1dbb0, 0xab5c5918, 0x946554fd, | |
| 182 0x8c2e680f, 0xeb3d799f, 0xb11ee0b7, 0x2d436b86, | |
| 183 0xda672e2a, 0x1588ca88, 0xe369735d, 0x904f35f7, | |
| 184 0xd7158fd6, 0x6fa6f051, 0x616e6b96, 0xac94efdc, | |
| 185 0x36413f93, 0xc622c298, 0xf5a42ab8, 0x8a88d77b, | |
| 186 0xf5ad9d0e, 0x8999220b, 0x27fb47b9 | |
| 187 }; | |
| 188 | |
| 189 /* FPTR and RPTR are two pointers into the state info, a front and a rear | |
| 190 pointer. These two pointers are always rand_sep places aparts, as they | |
| 191 cycle through the state information. (Yes, this does mean we could get | |
| 192 away with just one pointer, but the code for random is more efficient | |
| 193 this way). The pointers are left positioned as they would be from the call: | |
| 194 initstate(1, randtbl, 128); | |
| 195 (The position of the rear pointer, rptr, is really 0 (as explained above | |
| 196 in the initialization of randtbl) because the state table pointer is set | |
| 197 to point to randtbl[1] (as explained below).) */ | |
| 198 | |
| 199 static long int *fptr = &randtbl[SEP_3 + 1]; | |
| 200 static long int *rptr = &randtbl[1]; | |
| 201 | |
| 202 | |
| 203 | |
| 204 /* The following things are the pointer to the state information table, | |
| 205 the type of the current generator, the degree of the current polynomial | |
| 206 being used, and the separation between the two pointers. | |
| 207 Note that for efficiency of random, we remember the first location of | |
| 208 the state information, not the zeroeth. Hence it is valid to access | |
| 209 state[-1], which is used to store the type of the R.N.G. | |
| 210 Also, we remember the last location, since this is more efficient than | |
| 211 indexing every time to find the address of the last element to see if | |
| 212 the front and rear pointers have wrapped. */ | |
| 213 | |
| 214 static long int *state = &randtbl[1]; | |
| 215 | |
| 216 static int rand_type = TYPE_3; | |
| 217 static int rand_deg = DEG_3; | |
| 218 static int rand_sep = SEP_3; | |
| 219 | |
| 220 static long int *end_ptr = &randtbl[sizeof(randtbl) / sizeof(randtbl[0])]; | |
| 221 | |
| 222 /* Initialize the random number generator based on the given seed. If the | |
| 223 type is the trivial no-state-information type, just remember the seed. | |
| 224 Otherwise, initializes state[] based on the given "seed" via a linear | |
| 225 congruential generator. Then, the pointers are set to known locations | |
| 226 that are exactly rand_sep places apart. Lastly, it cycles the state | |
| 227 information a given number of times to get rid of any initial dependencies | |
| 228 introduced by the L.C.R.N.G. Note that the initialization of randtbl[] | |
| 229 for default usage relies on values produced by this routine. */ | |
| 230 void | |
| 231 srandom (unsigned int x) | |
| 232 { | |
| 233 state[0] = x; | |
| 234 if (rand_type != TYPE_0) | |
| 235 { | |
| 236 register long int i; | |
| 237 for (i = 1; i < rand_deg; ++i) | |
| 238 state[i] = (1103515145 * state[i - 1]) + 12345; | |
| 239 fptr = &state[rand_sep]; | |
| 240 rptr = &state[0]; | |
| 241 for (i = 0; i < 10 * rand_deg; ++i) | |
| 242 random(); | |
| 243 } | |
| 244 } | |
| 245 | |
| 246 /* Initialize the state information in the given array of N bytes for | |
| 247 future random number generation. Based on the number of bytes we | |
| 248 are given, and the break values for the different R.N.G.'s, we choose | |
| 249 the best (largest) one we can and set things up for it. srandom is | |
| 250 then called to initialize the state information. Note that on return | |
| 251 from srandom, we set state[-1] to be the type multiplexed with the current | |
| 252 value of the rear pointer; this is so successive calls to initstate won't | |
| 253 lose this information and will be able to restart with setstate. | |
| 254 Note: The first thing we do is save the current state, if any, just like | |
| 255 setstate so that it doesn't matter when initstate is called. | |
| 256 Returns a pointer to the old state. */ | |
| 257 PTR | |
| 258 initstate (unsigned int seed, PTR arg_state, unsigned long n) | |
| 259 { | |
| 260 PTR ostate = (PTR) &state[-1]; | |
| 261 | |
| 262 if (rand_type == TYPE_0) | |
| 263 state[-1] = rand_type; | |
| 264 else | |
| 265 state[-1] = (MAX_TYPES * (rptr - state)) + rand_type; | |
| 266 if (n < BREAK_1) | |
| 267 { | |
| 268 if (n < BREAK_0) | |
| 269 { | |
| 270 errno = EINVAL; | |
| 271 return NULL; | |
| 272 } | |
| 273 rand_type = TYPE_0; | |
| 274 rand_deg = DEG_0; | |
| 275 rand_sep = SEP_0; | |
| 276 } | |
| 277 else if (n < BREAK_2) | |
| 278 { | |
| 279 rand_type = TYPE_1; | |
| 280 rand_deg = DEG_1; | |
| 281 rand_sep = SEP_1; | |
| 282 } | |
| 283 else if (n < BREAK_3) | |
| 284 { | |
| 285 rand_type = TYPE_2; | |
| 286 rand_deg = DEG_2; | |
| 287 rand_sep = SEP_2; | |
| 288 } | |
| 289 else if (n < BREAK_4) | |
| 290 { | |
| 291 rand_type = TYPE_3; | |
| 292 rand_deg = DEG_3; | |
| 293 rand_sep = SEP_3; | |
| 294 } | |
| 295 else | |
| 296 { | |
| 297 rand_type = TYPE_4; | |
| 298 rand_deg = DEG_4; | |
| 299 rand_sep = SEP_4; | |
| 300 } | |
| 301 | |
| 302 state = &((long int *) arg_state)[1]; /* First location. */ | |
| 303 /* Must set END_PTR before srandom. */ | |
| 304 end_ptr = &state[rand_deg]; | |
| 305 srandom(seed); | |
| 306 if (rand_type == TYPE_0) | |
| 307 state[-1] = rand_type; | |
| 308 else | |
| 309 state[-1] = (MAX_TYPES * (rptr - state)) + rand_type; | |
| 310 | |
| 311 return ostate; | |
| 312 } | |
| 313 | |
| 314 /* Restore the state from the given state array. | |
| 315 Note: It is important that we also remember the locations of the pointers | |
| 316 in the current state information, and restore the locations of the pointers | |
| 317 from the old state information. This is done by multiplexing the pointer | |
| 318 location into the zeroeth word of the state information. Note that due | |
| 319 to the order in which things are done, it is OK to call setstate with the | |
| 320 same state as the current state | |
| 321 Returns a pointer to the old state information. */ | |
| 322 | |
| 323 PTR | |
| 324 setstate (PTR arg_state) | |
| 325 { | |
| 326 register long int *new_state = (long int *) arg_state; | |
| 327 register int type = new_state[0] % MAX_TYPES; | |
| 328 register int rear = new_state[0] / MAX_TYPES; | |
| 329 PTR ostate = (PTR) &state[-1]; | |
| 330 | |
| 331 if (rand_type == TYPE_0) | |
| 332 state[-1] = rand_type; | |
| 333 else | |
| 334 state[-1] = (MAX_TYPES * (rptr - state)) + rand_type; | |
| 335 | |
| 336 switch (type) | |
| 337 { | |
| 338 case TYPE_0: | |
| 339 case TYPE_1: | |
| 340 case TYPE_2: | |
| 341 case TYPE_3: | |
| 342 case TYPE_4: | |
| 343 rand_type = type; | |
| 344 rand_deg = degrees[type]; | |
| 345 rand_sep = seps[type]; | |
| 346 break; | |
| 347 default: | |
| 348 /* State info munged. */ | |
| 349 errno = EINVAL; | |
| 350 return NULL; | |
| 351 } | |
| 352 | |
| 353 state = &new_state[1]; | |
| 354 if (rand_type != TYPE_0) | |
| 355 { | |
| 356 rptr = &state[rear]; | |
| 357 fptr = &state[(rear + rand_sep) % rand_deg]; | |
| 358 } | |
| 359 /* Set end_ptr too. */ | |
| 360 end_ptr = &state[rand_deg]; | |
| 361 | |
| 362 return ostate; | |
| 363 } | |
| 364 | |
| 365 /* If we are using the trivial TYPE_0 R.N.G., just do the old linear | |
| 366 congruential bit. Otherwise, we do our fancy trinomial stuff, which is the | |
| 367 same in all ther other cases due to all the global variables that have been | |
| 368 set up. The basic operation is to add the number at the rear pointer into | |
| 369 the one at the front pointer. Then both pointers are advanced to the next | |
| 370 location cyclically in the table. The value returned is the sum generated, | |
| 371 reduced to 31 bits by throwing away the "least random" low bit. | |
| 372 Note: The code takes advantage of the fact that both the front and | |
| 373 rear pointers can't wrap on the same call by not testing the rear | |
| 374 pointer if the front one has wrapped. Returns a 31-bit random number. */ | |
| 375 | |
| 376 long int | |
| 377 random (void) | |
| 378 { | |
| 379 if (rand_type == TYPE_0) | |
| 380 { | |
| 381 state[0] = ((state[0] * 1103515245) + 12345) & LONG_MAX; | |
| 382 return state[0]; | |
| 383 } | |
| 384 else | |
| 385 { | |
| 386 long int i; | |
| 387 *fptr += *rptr; | |
| 388 /* Chucking least random bit. */ | |
| 389 i = (*fptr >> 1) & LONG_MAX; | |
| 390 ++fptr; | |
| 391 if (fptr >= end_ptr) | |
| 392 { | |
| 393 fptr = state; | |
| 394 ++rptr; | |
| 395 } | |
| 396 else | |
| 397 { | |
| 398 ++rptr; | |
| 399 if (rptr >= end_ptr) | |
| 400 rptr = state; | |
| 401 } | |
| 402 return i; | |
| 403 } | |
| 404 } |