| Authors: Rasmus Lerdorf <rasmus@lerdorf.on.ca> |
| Zeev Suraski <zeev@zend.com> |
| Pedro Melo <melo@ip.pt> |
- | Jeroen van Wolffelaar <jeroen@php.net> |
+ | |
+ | Based on code from: Shawn Cokus <Cokus@math.washington.edu> |
+----------------------------------------------------------------------+
*/
/* $Id$ */
#include "php.h"
#include "php_math.h"
#include "php_rand.h"
-#include "php_lcg.h"
-#include "php_ini.h"
-
-#include "zend_execute.h"
#include "basic_functions.h"
-/* See php_rand.h for information about layout */
-
-/* an ARRAY of POINTERS, not vice versa */
-php_randgen_entry *php_randgen_entries[PHP_RAND_NUMRANDS];
-
-#define PHP_HAS_SRAND(which) (php_randgen_entries[which] && php_randgen_entries[which]->srand)
-#define PHP_SRAND(which,seed) ((*(php_randgen_entries[which]->srand))(seed TSRMLS_CC))
-#define PHP_RAND(which) ((*(php_randgen_entries[which]->rand))(TSRMLS_C))
-#define PHP_RANDMAX(which) (php_randgen_entries[which]->randmax)
-#define PHP_RAND_INISTR(which) (php_randgen_entries[which]->ini_str)
-
-#define CURR_GEN BG(rand_generator_current)
-
-PHP_MINIT_FUNCTION(rand)
+/*
+ This is the ``Mersenne Twister'' random number generator MT19937, which
+ generates pseudorandom integers uniformly distributed in 0..(2^32 - 1)
+ starting from any odd seed in 0..(2^32 - 1). This version is a recode
+ by Shawn Cokus (Cokus@math.washington.edu) on March 8, 1998 of a version by
+ Takuji Nishimura (who had suggestions from Topher Cooper and Marc Rieffel in
+ July-August 1997).
+
+ Effectiveness of the recoding (on Goedel2.math.washington.edu, a DEC Alpha
+ running OSF/1) using GCC -O3 as a compiler: before recoding: 51.6 sec. to
+ generate 300 million random numbers; after recoding: 24.0 sec. for the same
+ (i.e., 46.5% of original time), so speed is now about 12.5 million random
+ number generations per second on this machine.
+
+ According to the URL <http://www.math.keio.ac.jp/~matumoto/emt.html>
+ (and paraphrasing a bit in places), the Mersenne Twister is ``designed
+ with consideration of the flaws of various existing generators,'' has
+ a period of 2^19937 - 1, gives a sequence that is 623-dimensionally
+ equidistributed, and ``has passed many stringent tests, including the
+ die-hard test of G. Marsaglia and the load test of P. Hellekalek and
+ S. Wegenkittl.'' It is efficient in memory usage (typically using 2506
+ to 5012 bytes of static data, depending on data type sizes, and the code
+ is quite short as well). It generates random numbers in batches of 624
+ at a time, so the caching and pipelining of modern systems is exploited.
+ It is also divide- and mod-free.
+
+ This library is free software; you can redistribute it and/or modify it
+ under the terms of the GNU Library General Public License as published by
+ the Free Software Foundation (either version 2 of the License or, at your
+ option, any later version). This library is distributed in the hope that
+ it will be useful, but WITHOUT ANY WARRANTY, without even the implied
+ warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See
+ the GNU Library General Public License for more details. You should have
+ received a copy of the GNU Library General Public License along with this
+ library; if not, write to the Free Software Foundation, Inc., 59 Temple
+ Place, Suite 330, Boston, MA 02111-1307, USA.
+
+ The code as Shawn received it included the following notice:
+
+ Copyright (C) 1997 Makoto Matsumoto and Takuji Nishimura. When
+ you use this, send an e-mail to <matumoto@math.keio.ac.jp> with
+ an appropriate reference to your work.
+
+ It would be nice to CC: <Cokus@math.washington.edu> when you write.
+
+
+
+ php_uint32 must be an unsigned integer type capable of holding at least 32
+ bits; exactly 32 should be fastest, but 64 is better on an Alpha with
+ GCC at -O3 optimization so try your options and see what's best for you
+
+ Melo: we should put some ifdefs here to catch those alphas...
+*/
+
+
+#define N MT_N /* length of state vector */
+#define M (397) /* a period parameter */
+#define K (0x9908B0DFU) /* a magic constant */
+#define hiBit(u) ((u) & 0x80000000U) /* mask all but highest bit of u */
+#define loBit(u) ((u) & 0x00000001U) /* mask all but lowest bit of u */
+#define loBits(u) ((u) & 0x7FFFFFFFU) /* mask the highest bit of u */
+#define mixBits(u, v) (hiBit(u)|loBits(v)) /* move hi bit of u to hi bit of v */
+
+#define MT_RAND_MAX ((long)(0x7FFFFFFF)) /* (1<<31) - 1 */
+
+/* {{{ seedMT
+ */
+static void seedMT(php_uint32 seed TSRMLS_DC)
{
- PHP_MINIT(rand_sys)(INIT_FUNC_ARGS_PASSTHRU);
- PHP_MINIT(rand_mt)(INIT_FUNC_ARGS_PASSTHRU);
- /* lcg not yet implemented */
- php_randgen_entries[PHP_RAND_LCG] = NULL;
-
- return SUCCESS;
+ /*
+ We initialize state[0..(N-1)] via the generator
+
+ x_new = (69069 * x_old) mod 2^32
+
+ from Line 15 of Table 1, p. 106, Sec. 3.3.4 of Knuth's
+ _The Art of Computer Programming_, Volume 2, 3rd ed.
+
+ Notes (SJC): I do not know what the initial state requirements
+ of the Mersenne Twister are, but it seems this seeding generator
+ could be better. It achieves the maximum period for its modulus
+ (2^30) iff x_initial is odd (p. 20-21, Sec. 3.2.1.2, Knuth); if
+ x_initial can be even, you have sequences like 0, 0, 0, ...;
+ 2^31, 2^31, 2^31, ...; 2^30, 2^30, 2^30, ...; 2^29, 2^29 + 2^31,
+ 2^29, 2^29 + 2^31, ..., etc. so I force seed to be odd below.
+
+ Even if x_initial is odd, if x_initial is 1 mod 4 then
+
+ the lowest bit of x is always 1,
+ the next-to-lowest bit of x is always 0,
+ the 2nd-from-lowest bit of x alternates ... 0 1 0 1 0 1 0 1 ... ,
+ the 3rd-from-lowest bit of x 4-cycles ... 0 1 1 0 0 1 1 0 ... ,
+ the 4th-from-lowest bit of x has the 8-cycle ... 0 0 0 1 1 1 1 0 ... ,
+ ...
+
+ and if x_initial is 3 mod 4 then
+
+ the lowest bit of x is always 1,
+ the next-to-lowest bit of x is always 1,
+ the 2nd-from-lowest bit of x alternates ... 0 1 0 1 0 1 0 1 ... ,
+ the 3rd-from-lowest bit of x 4-cycles ... 0 0 1 1 0 0 1 1 ... ,
+ the 4th-from-lowest bit of x has the 8-cycle ... 0 0 1 1 1 1 0 0 ... ,
+ ...
+
+ The generator's potency (min. s>=0 with (69069-1)^s = 0 mod 2^32) is
+ 16, which seems to be alright by p. 25, Sec. 3.2.1.3 of Knuth. It
+ also does well in the dimension 2..5 spectral tests, but it could be
+ better in dimension 6 (Line 15, Table 1, p. 106, Sec. 3.3.4, Knuth).
+
+ Note that the random number user does not see the values generated
+ here directly since reloadMT() will always munge them first, so maybe
+ none of all of this matters. In fact, the seed values made here could
+ even be extra-special desirable if the Mersenne Twister theory says
+ so-- that's why the only change I made is to restrict to odd seeds.
+ */
+
+ register php_uint32 x = (seed | 1U) & 0xFFFFFFFFU, *s = BG(state);
+ register int j;
+
+ for(BG(left)=0, *s++=x, j=N; --j;
+ *s++ = (x*=69069U) & 0xFFFFFFFFU);
}
+/* }}} */
-/* TODO: check that this function is called on the start of each script
- * execution: not more often, not less often.
- *
- * Note that system rand is inherently thread-unsafe: A different thread can
- * always eat up some rand()'s, and thus nuking your expected sequence.
- * Another reason to use MT...
- */
-PHP_RINIT_FUNCTION(rand)
+static php_uint32 reloadMT(TSRMLS_D)
{
- register int i;
-
- /* seed all number-generators */
- /* FIXME: or seed relevant numgen on init/update ini-entry? */
- for (i = 0 ; i < PHP_RAND_NUMRANDS ; i++) {
- if (PHP_HAS_SRAND(i)) {
-#define SRAND_A_RANDOM_SEED ((long)time(0) * (long)getpid() * (long)(php_combined_lcg(TSRMLS_C) * 10000.0)) /* something with microtime? */
- PHP_SRAND(i,SRAND_A_RANDOM_SEED);
- }
- }
+ register php_uint32 *p0=BG(state), *p2=BG(state)+2, *pM=BG(state)+M, s0, s1;
+ register int j;
- return SUCCESS;
-}
+ if(BG(left) < -1)
+ seedMT(4357U TSRMLS_CC);
-/* INI */
-static int randgen_str_to_int(char *str, int strlen)
-{
- register int i;
+ BG(left)=N-1, BG(next)=BG(state)+1;
- for (i = 0 ; i < PHP_RAND_NUMRANDS ; i++) {
- if (!strcasecmp(str, PHP_RAND_INISTR(i)))
- return i;
- }
- return -1;
-}
-
-/* FIXME: check that this is called on initial ini-parsing too */
-/* FIXME: what if no ini-entry was present? */
-static PHP_INI_MH(OnUpdateRandGen)
-{
- /* Set BG(rand_generator) to the correct integer value indicating
- * ini-setting */
- BG(rand_generator) = randgen_str_to_int(new_value, new_value_length);
- if (BG(rand_generator) == -1) {
- /* FIXME: is this possible? What happens if this occurs during
- * ini-parsing at startup? */
- php_error(E_WARNING,"Invalid value for random_number_generator: \"%s\"", new_value);
- /* Fallback: */
- BG(rand_generator) = PHP_RAND_DEFAULT;
- }
-#ifdef DEBUG_RAND
- printf("\nRAND-INI updated: %d\n",BG(rand_generator));
-#endif
- return SUCCESS;
-}
+ for(s0=BG(state)[0], s1=BG(state)[1], j=N-M+1; --j; s0=s1, s1=*p2++)
+ *p0++ = *pM++ ^ (mixBits(s0, s1) >> 1) ^ (loBit(s1) ? K : 0U);
+
+ for(pM=BG(state), j=M; --j; s0=s1, s1=*p2++)
+ *p0++ = *pM++ ^ (mixBits(s0, s1) >> 1) ^ (loBit(s1) ? K : 0U);
-PHP_INI_BEGIN()
- /* FIXME: default is hardcoded here, this is the second place */
- PHP_INI_ENTRY("random_number_generator", "mt", PHP_INI_ALL, OnUpdateRandGen)
-PHP_INI_END()
+ s1=BG(state)[0], *p0 = *pM ^ (mixBits(s0, s1) >> 1) ^ (loBit(s1) ? K : 0U);
+ s1 ^= (s1 >> 11);
+ s1 ^= (s1 << 7) & 0x9D2C5680U;
+ s1 ^= (s1 << 15) & 0xEFC60000U;
+ return(s1 ^ (s1 >> 18));
+}
-/* srand */
-/* FIXME: isn't used? */
-/* {{{ void php_srand(void) */
-static void php_srand(TSRMLS_D)
+static inline php_uint32 randomMT(void)
{
- CURR_GEN = BG(rand_generator);
- PHP_SRAND(BG(rand_generator), SRAND_A_RANDOM_SEED);
-}
-/* }}} */
+ php_uint32 y;
+ TSRMLS_FETCH();
+
+ if(--BG(left) < 0)
+ return(reloadMT(TSRMLS_C));
-/* {{{ [mt_]srand common */
-#define pim_srand_common(name,type) \
-PHP_FUNCTION(name) \
-{ \
- zval **seed; \
- zval **alg; \
- \
- switch (ZEND_NUM_ARGS()) { \
- case 0: \
- CURR_GEN = BG(rand_generator); \
- PHP_SRAND(BG(rand_generator), SRAND_A_RANDOM_SEED); \
- RETURN_TRUE; \
- case 1: \
- zend_get_parameters_ex(1, &seed); \
- convert_to_long_ex(seed); \
- CURR_GEN = type; \
- PHP_SRAND(type, Z_LVAL_PP(seed)); \
- RETURN_TRUE; \
- case 2: \
- /* algorithm, seed is most logic, though it is the other way
- * around than current way... */ \
- zend_get_parameters_ex(2, &alg, &seed); \
- convert_to_long_ex(seed); \
- convert_to_long_ex(alg); \
- if (0 > Z_LVAL_PP(alg) || Z_LVAL_PP(alg) >= PHP_RAND_NUMRANDS) { \
- php_error(E_WARNING, "%s(): There is no algorithm %d.", get_active_function_name(TSRMLS_C), Z_LVAL_PP(alg)); \
- RETURN_FALSE; \
- } \
- if (!PHP_HAS_SRAND(Z_LVAL_PP(alg))) { \
- php_error(E_WARNING, "%s(): Algorithm %d does not support reproducable results.", get_active_function_name(TSRMLS_C), Z_LVAL_PP(alg)); \
- RETURN_FALSE; \
- } \
- CURR_GEN = Z_LVAL_PP(alg); \
- PHP_SRAND(Z_LVAL_PP(alg), Z_LVAL_PP(seed)); \
- RETURN_TRUE; \
- default: \
- WRONG_PARAM_COUNT; \
- } \
+ y = *BG(next)++;
+ y ^= (y >> 11);
+ y ^= (y << 7) & 0x9D2C5680U;
+ y ^= (y << 15) & 0xEFC60000U;
+ return(y ^ (y >> 18));
}
-/* }}} */
-/* {{{ proto bool srand(int seed)
+/* {{{ proto void srand(int seed)
Seeds random number generator */
-pim_srand_common(srand,PHP_RAND_SYS)
-/* }}} */
+PHP_FUNCTION(srand)
+{
+ pval **arg;
-/* {{{ proto bool mt_srand(int seed)
- Seeds random number generator */
-pim_srand_common(mt_srand,PHP_RAND_MT)
+ if (ZEND_NUM_ARGS() != 1 || zend_get_parameters_ex(1, &arg) == FAILURE) {
+ WRONG_PARAM_COUNT;
+ }
+ convert_to_long_ex(arg);
+ php_srand((*arg)->value.lval);
+}
/* }}} */
-/* rand */
-
-/* {{{ PHPAPI long php_rand(void) */
-PHPAPI long php_rand(TSRMLS_D)
+/* {{{ proto void mt_srand(int seed)
+ Seeds Mersenne Twister random number generator */
+PHP_FUNCTION(mt_srand)
{
- return PHP_RAND(CURR_GEN);
+ pval **arg;
+
+ if (ZEND_NUM_ARGS() != 1 || zend_get_parameters_ex(1, &arg) == FAILURE) {
+ WRONG_PARAM_COUNT;
+ }
+ convert_to_long_ex(arg);
+ seedMT((*arg)->value.lval TSRMLS_CC);
}
/* }}} */
-/* {{{ PHPAPI double php_drand(void)
- * returns a double in the range [0,1) */
-PHPAPI double php_drand(TSRMLS_D)
+/* {{{ proto int rand([int min, int max])
+ Returns a random number */
+PHP_FUNCTION(rand)
{
- return (double)php_rand(TSRMLS_C) /
- (double)(PHP_RANDMAX(CURR_GEN)+1.0);
-}
-/* }}} */
+ pval **p_min=NULL, **p_max=NULL;
+
+ switch (ZEND_NUM_ARGS()) {
+ case 0:
+ break;
+ case 2:
+ if (zend_get_parameters_ex(2, &p_min, &p_max)==FAILURE) {
+ RETURN_FALSE;
+ }
+ convert_to_long_ex(p_min);
+ convert_to_long_ex(p_max);
+ if ((*p_max)->value.lval-(*p_min)->value.lval < 0) {
+ php_error(E_WARNING, "rand(): Invalid range: %ld..%ld", (*p_min)->value.lval, (*p_max)->value.lval);
+ } else if ((*p_max)->value.lval-(*p_min)->value.lval > PHP_RAND_MAX){
+ php3_error(E_WARNING, "rand(): Invalid range: %ld..%ld", (*p_min)->value.lval, (*p_max)->value.lval);
+ }
+ break;
+ default:
+ WRONG_PARAM_COUNT;
+ break;
+ }
+
+ return_value->type = IS_LONG;
+
+ return_value->value.lval = php_rand();
-/* {{{ macro: PHP_RAND_RANGE */
-#define PHP_RAND_RANGE(which,min,max,result) { \
/*
* A bit of tricky math here. We want to avoid using a modulus because
* that simply tosses the high-order bits and might skew the distribution
* of random values over the range. Instead we map the range directly.
*
* We need to map the range from 0...M evenly to the range a...b
- * Expressed in real numbers, this becomes:
- *
- * [0,M+1[ mapped to [a,b+1[
- *
* Let n = the random number and n' = the mapped random number
- * So the formula needs to be:
- *
- * n' = a + n((b+1)-a)/(m+1)
*
- * This isn't perfect, because n only takes integer values. So when a..b
- * spans a significant portion of 0..M, some numbers have nearly twice as
- * much chance. But since twice a very small chance is still a very small
- * chance, it's ignored.
- *
- * --Rasmus and Jeroen
- */ \
- (result) = PHP_RAND(which); \
- if ((max) < (min)) { \
- php_error(E_WARNING, "%s(): Invalid range: %ld..%ld (minimum can't be larger than maximum)", \
- get_active_function_name(TSRMLS_C), (min), (max)); \
- } else if ( (max) - (min) > PHP_RANDMAX(which) ) { \
- /* TODO: this can done better, get two numbers and combine... */ \
- php_error(E_WARNING, "%s(): Invalid range: %ld..%ld (can't give that much randomness)", \
- get_active_function_name(TSRMLS_C), (min), (max)); \
- } \
- (result) = (min) + (long) ((double)((max)-(min)+1) * (result)/(PHP_RANDMAX(which)+1.0)); \
-}
-/* }}} */
-
-/* {{{ PHPAPI long php_rand_range(long min, long max) */
-PHPAPI long php_rand_range(long min, long max TSRMLS_DC)
-{
- register long result;
-
- PHP_RAND_RANGE(CURR_GEN, min, max, result);
- return result;
-}
-/* }}} */
-
-/* {{{ [mt_]rand common */
-#define PHP_FUNCTION_RAND(name,which) \
-PHP_FUNCTION(name) \
-{ \
- zval **min, **max; \
- \
- switch (ZEND_NUM_ARGS()) { \
- case 0: \
- RETURN_LONG(PHP_RAND(which)); \
- case 2: \
- if (zend_get_parameters_ex(2, &min, &max)==FAILURE) { \
- RETURN_FALSE; \
- } \
- convert_to_long_ex(min); \
- convert_to_long_ex(max); \
- Z_TYPE_P(return_value) = IS_LONG; \
- PHP_RAND_RANGE(which, Z_LVAL_PP(min), \
- Z_LVAL_PP(max), Z_LVAL_P(return_value)); \
- return; \
- default: \
- WRONG_PARAM_COUNT; \
- break; \
- } \
+ * Then we have: n' = a + n(b-a)/M
+ *
+ * We have a problem here in that only n==M will get mapped to b which
+ # means the chances of getting b is much much less than getting any of
+ # the other values in the range. We can fix this by increasing our range
+ # artifically and using:
+ #
+ # n' = a + n(b-a+1)/M
+ *
+ # Now we only have a problem if n==M which would cause us to produce a
+ # number of b+1 which would be bad. So we bump M up by one to make sure
+ # this will never happen, and the final algorithm looks like this:
+ #
+ # n' = a + n(b-a+1)/(M+1)
+ *
+ * -RL
+ */
+ if (p_min && p_max) { /* implement range */
+ return_value->value.lval = (*p_min)->value.lval +
+ (int)((double)((*p_max)->value.lval - (*p_min)->value.lval + 1.0) * return_value->value.lval/(PHP_RAND_MAX+1.0));
+ }
}
/* }}} */
-/* {{{ proto int rand([int min, int max])
- Returns a random number */
-PHP_FUNCTION_RAND(rand,PHP_RAND_SYS)
-/* }}} */
-
-/* {{{ proto int mt_rand([int min, int max])
- Returns a random number by means of Mersenne Twister */
-PHP_FUNCTION_RAND(mt_rand,PHP_RAND_MT)
-/* }}} */
-
-/* getrandmax */
-
-/* {{{ PHPAPI long php_randmax(void)
- Returns the maximum value a random number can have */
-PHPAPI long php_randmax(TSRMLS_D)
+/* {{{ proto int mt_rand([int min, int max])
+ Returns a random number from Mersenne Twister */
+PHP_FUNCTION(mt_rand)
{
- return PHP_RANDMAX(CURR_GEN);
+ pval **p_min=NULL, **p_max=NULL;
+
+ switch (ZEND_NUM_ARGS()) {
+ case 0:
+ break;
+ case 2:
+ if (zend_get_parameters_ex(2, &p_min, &p_max)==FAILURE) {
+ RETURN_FALSE;
+ }
+ convert_to_long_ex(p_min);
+ convert_to_long_ex(p_max);
+ if ((*p_max)->value.lval-(*p_min)->value.lval <= 0) {
+ php_error(E_WARNING, "mt_rand(): Invalid range: %ld..%ld", (*p_min)->value.lval, (*p_max)->value.lval);
+ }else if ((*p_max)->value.lval-(*p_min)->value.lval > MT_RAND_MAX){
+ php3_error(E_WARNING, "mt_rand(): Invalid range: %ld..%ld", (*p_min)->value.lval, (*p_max)->value.lval);
+ }
+ break;
+ default:
+ WRONG_PARAM_COUNT;
+ break;
+ }
+
+ return_value->type = IS_LONG;
+ /*
+ * Melo: hmms.. randomMT() returns 32 random bits...
+ * Yet, the previous php_rand only returns 31 at most.
+ * So I put a right shift to loose the lsb. It *seems*
+ * better than clearing the msb.
+ * Update:
+ * I talked with Cokus via email and it won't ruin the algorithm
+ */
+ return_value->value.lval = (long)(randomMT() >> 1);
+
+ if (p_min && p_max) { /* implement range */
+ return_value->value.lval = (*p_min)->value.lval +
+ (long)((double)((*p_max)->value.lval - (*p_min)->value.lval + 1.0) * return_value->value.lval/(MT_RAND_MAX+1.0));
+ }
}
/* }}} */
WRONG_PARAM_COUNT;
}
- RETURN_LONG( php_randmax(TSRMLS_C));
+ return_value->type = IS_LONG;
+ return_value->value.lval = PHP_RAND_MAX;
}
/* }}} */
/* {{{ proto int mt_getrandmax(void)
- Returns the maximum value a random number can have */
+ Returns the maximum value a random number from Mersenne Twister can have */
PHP_FUNCTION(mt_getrandmax)
{
if (ZEND_NUM_ARGS() != 0) {
WRONG_PARAM_COUNT;
}
- RETURN_LONG( php_randmax(TSRMLS_C) );
+ return_value->type = IS_LONG;
+ /*
+ * Melo: it could be 2^^32 but we only use 2^^31 to maintain
+ * compatibility with the previous php_rand
+ */
+ return_value->value.lval = MT_RAND_MAX; /* 2^^31 */
}
/* }}} */
* c-basic-offset: 4
* End:
* vim600: sw=4 ts=4 tw=78 fdm=marker
- * vim: sw=4 ts=4 tw=78
+ * vim<600: sw=4 ts=4 tw=78
*/
+++ /dev/null
-/*
- +----------------------------------------------------------------------+
- | PHP version 4.0 |
- +----------------------------------------------------------------------+
- | Copyright (c) 1997-2001 The PHP Group |
- +----------------------------------------------------------------------+
- | This source file is subject to version 2.02 of the PHP license, |
- | that is bundled with this package in the file LICENSE, and is |
- | available at through the world-wide-web at |
- | http://www.php.net/license/2_02.txt. |
- | If you did not receive a copy of the PHP license and are unable to |
- | obtain it through the world-wide-web, please send a note to |
- | license@php.net so we can mail you a copy immediately. |
- +----------------------------------------------------------------------+
- | Authors: Rasmus Lerdorf <rasmus@lerdorf.on.ca> |
- | Zeev Suraski <zeev@zend.com> |
- | Pedro Melo <melo@ip.pt> |
- | Jeroen van Wolffelaar <jeroen@php.net> |
- | |
- | Based on code from: Shawn Cokus <Cokus@math.washington.edu> |
- +----------------------------------------------------------------------+
- */
-/* $Id$ */
-
-#include <stdlib.h>
-
-#include "php.h"
-#include "php_rand.h"
-
-#include "basic_functions.h"
-
-/*
- This is the ``Mersenne Twister'' random number generator MT19937, which
- generates pseudorandom integers uniformly distributed in 0..(2^32 - 1)
- starting from any odd seed in 0..(2^32 - 1). This version is a recode
- by Shawn Cokus (Cokus@math.washington.edu) on March 8, 1998 of a version by
- Takuji Nishimura (who had suggestions from Topher Cooper and Marc Rieffel in
- July-August 1997).
-
- Effectiveness of the recoding (on Goedel2.math.washington.edu, a DEC Alpha
- running OSF/1) using GCC -O3 as a compiler: before recoding: 51.6 sec. to
- generate 300 million random numbers; after recoding: 24.0 sec. for the same
- (i.e., 46.5% of original time), so speed is now about 12.5 million random
- number generations per second on this machine.
-
- According to the URL <http://www.math.keio.ac.jp/~matumoto/emt.html>
- (and paraphrasing a bit in places), the Mersenne Twister is ``designed
- with consideration of the flaws of various existing generators,'' has
- a period of 2^19937 - 1, gives a sequence that is 623-dimensionally
- equidistributed, and ``has passed many stringent tests, including the
- die-hard test of G. Marsaglia and the load test of P. Hellekalek and
- S. Wegenkittl.'' It is efficient in memory usage (typically using 2506
- to 5012 bytes of static data, depending on data type sizes, and the code
- is quite short as well). It generates random numbers in batches of 624
- at a time, so the caching and pipelining of modern systems is exploited.
- It is also divide- and mod-free.
-
- This library is free software; you can redistribute it and/or modify it
- under the terms of the GNU Library General Public License as published by
- the Free Software Foundation (either version 2 of the License or, at your
- option, any later version). This library is distributed in the hope that
- it will be useful, but WITHOUT ANY WARRANTY, without even the implied
- warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See
- the GNU Library General Public License for more details. You should have
- received a copy of the GNU Library General Public License along with this
- library; if not, write to the Free Software Foundation, Inc., 59 Temple
- Place, Suite 330, Boston, MA 02111-1307, USA.
-
- The code as Shawn received it included the following notice:
-
- Copyright (C) 1997 Makoto Matsumoto and Takuji Nishimura. When
- you use this, send an e-mail to <matumoto@math.keio.ac.jp> with
- an appropriate reference to your work.
-
- It would be nice to CC: <Cokus@math.washington.edu> when you write.
-
-
-
- php_uint32 must be an unsigned integer type capable of holding at least 32
- bits; exactly 32 should be fastest, but 64 is better on an Alpha with
- GCC at -O3 optimization so try your options and see what's best for you
-
- Melo: we should put some ifdefs here to catch those alphas...
-*/
-
-static void _php_srand_mt(long seed TSRMLS_DC);
-static inline long _php_rand_mt_reload(TSRMLS_D);
-static long _php_rand_mt(TSRMLS_D);
-/*
- * Melo: it could be 2^^32 but we only use 2^^31 to maintain
- * compatibility with the previous php_rand
- */
-#define PHP_RANDMAX_MT ((long)(0x7FFFFFFF)) /* 2^^31 - 1 */
-
-PHP_MINIT_FUNCTION(rand_mt)
-{
- PHP_RANDGEN_ENTRY(PHP_RAND_MT,
- _php_srand_mt, /* void srand(long seed) */
- _php_rand_mt, /* long rand(void) */
- PHP_RANDMAX_MT, /* long randmax */
- "mt" /* char *ini_str */
- );
-
- return SUCCESS;
-}
-
-#define N MT_N /* length of state vector */
-#define M (397) /* a period parameter */
-#define K (0x9908B0DFU) /* a magic constant */
-#define hiBit(u) ((u) & 0x80000000U) /* mask all but highest bit of u */
-#define loBit(u) ((u) & 0x00000001U) /* mask all but lowest bit of u */
-#define loBits(u) ((u) & 0x7FFFFFFFU) /* mask the highest bit of u */
-#define mixBits(u, v) (hiBit(u)|loBits(v)) /* move hi bit of u to hi bit of v */
-
-#define MIX_AND_RETURN(var) { \
- (var) ^= ((var) >> 11); \
- (var) ^= ((var) << 7) & 0x9D2C5680U; \
- (var) ^= ((var) << 15) & 0xEFC60000U; \
- (var) ^= ((var) >> 18); \
- /*
- * Melo: hmms.. these are 32 random bits...
- * Yet, the previous php_rand only returns 31 at most.
- * So I put a right shift to loose the lsb. It *seems*
- * better than clearing the msb.
- * Update:
- * I talked with Cokus via email and it won't ruin the algorithm
- *
- * Jeroen: moved this to end of php_rand_mt and php_rand_mt_reload
- */ \
- return (long)((var) >> 1); \
-}
-
-/* {{{ void _php_srand_mt(long seed)
- */
-static void _php_srand_mt(long seed TSRMLS_DC)
-{
- /*
- We initialize state[0..(N-1)] via the generator
-
- x_new = (69069 * x_old) mod 2^32
-
- from Line 15 of Table 1, p. 106, Sec. 3.3.4 of Knuth's
- _The Art of Computer Programming_, Volume 2, 3rd ed.
-
- Notes (SJC): I do not know what the initial state requirements
- of the Mersenne Twister are, but it seems this seeding generator
- could be better. It achieves the maximum period for its modulus
- (2^30) iff x_initial is odd (p. 20-21, Sec. 3.2.1.2, Knuth); if
- x_initial can be even, you have sequences like 0, 0, 0, ...;
- 2^31, 2^31, 2^31, ...; 2^30, 2^30, 2^30, ...; 2^29, 2^29 + 2^31,
- 2^29, 2^29 + 2^31, ..., etc. so I force seed to be odd below.
-
- Even if x_initial is odd, if x_initial is 1 mod 4 then
-
- the lowest bit of x is always 1,
- the next-to-lowest bit of x is always 0,
- the 2nd-from-lowest bit of x alternates ... 0 1 0 1 0 1 0 1 ... ,
- the 3rd-from-lowest bit of x 4-cycles ... 0 1 1 0 0 1 1 0 ... ,
- the 4th-from-lowest bit of x has the 8-cycle ... 0 0 0 1 1 1 1 0 ... ,
- ...
-
- and if x_initial is 3 mod 4 then
-
- the lowest bit of x is always 1,
- the next-to-lowest bit of x is always 1,
- the 2nd-from-lowest bit of x alternates ... 0 1 0 1 0 1 0 1 ... ,
- the 3rd-from-lowest bit of x 4-cycles ... 0 0 1 1 0 0 1 1 ... ,
- the 4th-from-lowest bit of x has the 8-cycle ... 0 0 1 1 1 1 0 0 ... ,
- ...
-
- The generator's potency (min. s>=0 with (69069-1)^s = 0 mod 2^32) is
- 16, which seems to be alright by p. 25, Sec. 3.2.1.3 of Knuth. It
- also does well in the dimension 2..5 spectral tests, but it could be
- better in dimension 6 (Line 15, Table 1, p. 106, Sec. 3.3.4, Knuth).
-
- Note that the random number user does not see the values generated
- here directly since reloadMT() will always munge them first, so maybe
- none of all of this matters. In fact, the seed values made here could
- even be extra-special desirable if the Mersenne Twister theory says
- so-- that's why the only change I made is to restrict to odd seeds.
- */
-
- register php_uint32 x = ((php_uint32)seed | 1U) & 0xFFFFFFFFU, *s = BG(state);
- register int j;
-
- for(BG(left)=0, *s++=x, j=N; --j;
- *s++ = (x*=69069U) & 0xFFFFFFFFU);
-}
-/* }}} */
-
-/* {{{ long _php_rand_mt_reload(void) [internal function]
- * Generates a new batch of random numbers, and returns the first of it */
-static inline long _php_rand_mt_reload(TSRMLS_D)
-{
- register php_uint32 *p0=BG(state), *p2=BG(state)+2, *pM=BG(state)+M, s0, s1;
- register int j;
-
- if(BG(left) < -1)
- _php_srand_mt(4357U TSRMLS_CC);
-
- BG(left)=N-1, BG(next)=BG(state)+1;
-
- for(s0=BG(state)[0], s1=BG(state)[1], j=N-M+1; --j; s0=s1, s1=*p2++)
- *p0++ = *pM++ ^ (mixBits(s0, s1) >> 1) ^ (loBit(s1) ? K : 0U);
-
- for(pM=BG(state), j=M; --j; s0=s1, s1=*p2++)
- *p0++ = *pM++ ^ (mixBits(s0, s1) >> 1) ^ (loBit(s1) ? K : 0U);
-
- s1=BG(state)[0], *p0 = *pM ^ (mixBits(s0, s1) >> 1) ^ (loBit(s1) ? K : 0U);
- MIX_AND_RETURN(s1);
-}
-/*}}}*/
-
-/* {{{ long _php_rand_mt(void) */
-static long _php_rand_mt(TSRMLS_D)
-{
- php_uint32 y;
-
- if(--BG(left) < 0)
- return(_php_rand_mt_reload(TSRMLS_C));
-
- y = *BG(next)++;
- MIX_AND_RETURN(y);
-}
-/* }}} */
-
-/*
- * Local variables:
- * tab-width: 4
- * c-basic-offset: 4
- * End:
- * vim600: sw=4 ts=4 tw=78 fdm=marker
- * vim<600: sw=4 ts=4 tw=78
- */
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