-/* ya_random -- Yet Another Random Number Generator.
+/* yarandom.c -- Yet Another Random Number Generator.
The unportable mess that is rand(), random(), drand48() and friends led me
to ask Phil Karlton <karlton@netscape.com> what the Right Thing to Do was.
k=20 and m=2^32."
So there you have it.
+
+ ---------------------------
+ Note: xlockmore 4.03a10 uses this very simple RNG:
+
+ if ((seed = seed % 44488 * 48271 - seed / 44488 * 3399) < 0)
+ seed += 2147483647;
+ return seed-1;
+
+ of which it says
+
+ ``Dr. Park's algorithm published in the Oct. '88 ACM "Random Number
+ Generators: Good Ones Are Hard To Find" His version available at
+ ftp://cs.wm.edu/pub/rngs.tar Present form by many authors.''
+
+ Karlton says: ``the usual problem with that kind of RNG turns out to
+ be unexepected short cycles for some word lengths.''
+
+ Karlton's RNG is faster, since it does three adds and two stores, while the
+ xlockmore RNG does two multiplies, two divides, three adds, and one store.
+
+ Compiler optimizations make a big difference here:
+ gcc -O: difference is 1.2x.
+ gcc -O2: difference is 1.4x.
+ gcc -O3: difference is 1.5x.
+ SGI cc -O: difference is 2.4x.
+ SGI cc -O2: difference is 2.4x.
+ SGI cc -O3: difference is 5.1x.
+ Irix 6.2; Indy r5k; SGI cc version 6; gcc version 2.7.2.1.
*/
-#include <unistd.h> /* for getpid() */
+
+#ifdef HAVE_CONFIG_H
+# include "config.h"
+#endif
+
+#ifdef HAVE_UNISTD_H
+# include <unistd.h> /* for getpid() */
+#endif
#include <sys/time.h> /* for gettimeofday() */
+#include "yarandom.h"
+
/* The following 'random' numbers are taken from CRC, 18th Edition, page 622.
Each array element was taken from the corresponding line in the table,
static int i1, i2;
-unsigned int ya_random()
+unsigned int
+ya_random (void)
{
register int ret = a[i1] + a[i2];
a[i1] = ret;
- i1 = i1 >= VectorSize ? 0 : i1 + 1;
- i2 = i2 >= VectorSize ? 0 : i2 + 1;
+ if (++i1 >= VectorSize) i1 = 0;
+ if (++i2 >= VectorSize) i2 = 0;
return ret;
}
-void ya_rand_init(seed)
- register unsigned int seed;
+void
+ya_rand_init(unsigned int seed)
{
int i;
if (seed == 0)
{
struct timeval tp;
+#ifdef GETTIMEOFDAY_TWO_ARGS
struct timezone tzp;
gettimeofday(&tp, &tzp);
+#else
+ gettimeofday(&tp);
+#endif
/* ignore overflow */
seed = (999*tp.tv_sec) + (1001*tp.tv_usec) + (1003 * getpid());
}