Subject:
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new version of Rich Drushel's random.c libarary for IC
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Newsgroups:
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lugnet.robotics.handyboard
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Date:
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Thu, 15 Jun 2000 14:52:49 GMT
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Original-From:
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Richard Drushel <(drushel@)stopspam(apk.net)>
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Viewed:
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865 times
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I have created a new and better version of my random.c IC library
for pseudo-random number generation. The old version had an algorithm that
I cooked up myself, and while it was fun to program, and fun to get working
in a multitasking environment (locking state machines and all that), the
truth is, the algorithm was not very random.
The new version implements the ran0() generator from "Numerical
Methods in C", version 2.0 (1992), pp. 278-279. I have preserved the
calling interface to my old random.c functions, however, so all existing
code should be completely compatible with the new random.c. I also added
some new functions, much requested by my Autonomous Robotics students, to
generate random numbers between any specified range.
So, if you're using my old random.c, *please* throw it away and
replace it with the new one, available via anonymous ftp at:
ftp://junior.apk.net/pub/users/drushel/rfd-ic/random.c
The old random.c is still there, renamed to random_old.c.
This code was developed and tested using the freeware 2.81 version
of IC, and runs on both Handy Boards and 6.270 boards. It is no longer
dependent upon my math.c math function library.
What follows are (1) function descriptions, and (2) results of
the benchmarking and statistical validation tests I did on the old and
new versions of the pseudo-random number generators. The new code is
much smaller, much more random, and 3x faster.
If you have any questions or comments, please let me know. I
apologize for how kludgy and unrandom the old version of random.c was; but
life is a learning experience, right? :-)
*Rich*
/*****************************************************************************/
/* */
/* PUBLIC FUNCTIONS: */
/* */
/* These functions may be used freely by user programs. */
/* */
/* int random(int mod) ;Random integers from peeking at 2 MHz system */
/* ;clock. mod is a modulo value which can range */
/* ;2 to 32767. */
/* ;Code by Fred G. Martin from lib_hb.c */
/* ;Note by RFD: provided for backward */
/* ;compatibility with existing code. Use in new */
/* ;programs is not encouraged. */
/* */
/* void randomize(int seed) ;Reseeds random number generator to user- */
/* ;defined seed */
/* ;Non-reentrant, so waits until busy flag */
/* ;_RND_BUSY is cleared. */
/* ;Originally made thread-safe by DFM */
/* ;4/27/1997 */
/* */
/* float rndf01(int arg) ;Returns a pseudo-random number (float, range */
/* ;0 to 1) based on value of arg: */
/* ; arg>0 returns random number */
/* ; arg==0 returns last random number (for debug) */
/* ; arg<0 reseeds random number generator */
/* with the last randomize() seed value */
/* and returns the first number in that */
/* series */
/* ;rndf01() is the common workhorse routine for */
/* ;All the other random number routines *except* */
/* ;random(). */
/* ;Note: rndf01() is *NOT* reentrant!! */
/* ;It sets a busy flag _RND_BUSY if another */
/* ;process is currently calling rndf01(). */
/* ;Originally made thread-safe by DFM 4/24/1997 */
/* */
/* int rnd(int arg) ;Returns a pseudo-random number (16-bit signed */
/* ;int, range -32768 to 32767) based on value of */
/* ;arg, as in rndf01(). */
/* ;Provided for backward compatibility with <2.0 */
/* ;versions of random.c. Now identical to */
/* ;rndrangei(-32768,32767,arg). */
/* */
/* int rndrangei(int ilo, int ihi, int arg) ;Returns a pseudo-random */
/* ;number (16-bit signed int) */
/* ;in the range ilo to ihi. */
/* ;arg is as in rndf01(). */
/* */
/* float rndrangef(float flo, float fhi, int arg) ;Returns a pseudo-random */
/* ;number (float) in the */
/* ;range flo to fhi. arg */
/* ;is as in rndf01(). */
/* ;This routine is used by */
/* ;all the rndrange_() */
/* ;functions. */
/* */
/* long rndrangel(long llo, long lhi, int arg) ;Returns a pseudo-random */
/* ;number (32-bit signed long) */
/* ;in the range llo to lhi. */
/* ;arg is as in rndf01(). */
/* */
/*****************************************************************************/
/* ; random.c RAM footprint (bytes) */
/* ;=============================================== */
/* ; v1.2 984 */
/* ; v2.0 486 */
/* */
/* ; statistical information */
/* ; (30000 calls, scaled to 0-99, binsize 1, mean */
/* ; counts/bin, standard error of the mean, min */
/* ; counts/bin, max counts/bin) */
/* ;=============================================== */
/* ; mean s.e.m. min max */
/* ; random() 300.00 15.00 0 587 */
/* ; pre-2.0 rnd() 300.00 34.84 14 2858 */
/* ; 2.0 rnd() 300.00 1.66 256 345 */
/* ; rndf01() 300.00 1.66 256 356 */
/* ; MS QuickBASIC 4.5 300.00 1.73 261 342 */
/* */
/* ; timing information */
/* ; (mean of 30000 calls, msec/value) */
/* ;=============================================== */
/* ; random() 1.68 */
/* ; pre-2.0 rnd() 28.88 */
/* ; 2.0 rnd() 10.16 */
/* ; rndf01() 7.76 */
/* ; rndrangei() 9.94 */
/* ; rndrangef() 9.36 */
/* ; rndrangel() 10.84 */
/* */
--
Richard F. Drushel, Ph.D. | "Aplysia californica" is your taxonomic
Department of Biology, Slug Division | nomenclature. / A slug, by any other
Case Western Reserve University | name, is still a slug by nature.
Cleveland, Ohio 44106-7080 U.S.A. | -- apologies to Data, "Ode to Spot"
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