src/common/urand.c

#ifndef lint
static const char       RCSid[] = "$Id$";
#endif
/*
 * Anticorrelated random function due to Christophe Schlick
 */

#include "copyright.h"

#include  <stdlib.h>
#include  "random.h"

#undef initurand

#define  MAXORDER       (8*sizeof(unsigned short))

unsigned short  *urperm = NULL; /* urand() permutation */
int  urmask;            /* bits used in permutation */

int
initurand(size)         /* initialize urand() for size entries */
int  size;
{
        int  order, n;
        register int  i, offset;

        if (urperm != NULL)
                free((void *)urperm);
        if (--size <= 0) {
                urperm = NULL;
                urmask = 0;
                return(0);
        }
        for (i = 1; size >>= 1; i++)
                ;
        order = i>MAXORDER ? MAXORDER : i;
        urmask = (1<<i) - 1;
        urperm = (unsigned short *)malloc((urmask+1)*sizeof(unsigned short));
        if (urperm == NULL) {
                eputs("out of memory in initurand\n");
                quit(1);
        }
        urperm[0] = 0;
        for (n = 1, offset = 1; n <= order; n++, offset <<= 1)
                for (i = offset; i--; ) {
                        urperm[i] =
                        urperm[i+offset] = 2*urperm[i];
                        if (random() & 0x4000)
                                urperm[i]++;
                        else
                                urperm[i+offset]++;
                }
        return(1<<order);
}


int
ilhash(d, n)                    /* hash a set of integer values */
register int  *d;
register int  n;
{
        static int  tab[8] = {13623,353,1637,5831,2314,3887,5832,8737};
        register int  hval;

        hval = 0;
        while (n-- > 0)
                hval += *d++ * tab[n&7];
        return(hval);
}
Revision:	2.6
Committed:	Tue Feb 25 02:47:22 2003 UTC (22 years, 8 months ago) by greg
Content type:	text/plain
Branch:	MAIN
CVS Tags:	rad3R5
Changes since 2.5:	+1 -56 lines
Log Message:	Replaced inline copyright notice with #include "copyright.h"
#	User	Rev	Content
1	greg	1.1	#ifndef lint
2	greg	2.5	static const char RCSid[] = "$Id$";
3	greg	1.1	#endif
4			/*
5	greg	1.5	* Anticorrelated random function due to Christophe Schlick
6	greg	1.1	*/
7
8	greg	2.6	#include "copyright.h"
9	greg	2.5
10			#include <stdlib.h>
11	greg	1.1	#include "random.h"
12
13	greg	2.5	#undef initurand
14	greg	1.1
15	gregl	2.4	#define MAXORDER (8*sizeof(unsigned short))
16
17			unsigned short urperm = NULL; / urand() permutation */
18	greg	1.1	int urmask; /* bits used in permutation */
19
20	gregl	2.3	int
21	greg	1.1	initurand(size) /* initialize urand() for size entries */
22			int size;
23			{
24			int order, n;
25			register int i, offset;
26
27	greg	2.2	if (urperm != NULL)
28	greg	2.5	free((void *)urperm);
29			if (--size <= 0) {
30			urperm = NULL;
31			urmask = 0;
32			return(0);
33			}
34	greg	1.1	for (i = 1; size >>= 1; i++)
35			;
36	gregl	2.4	order = i>MAXORDER ? MAXORDER : i;
37	greg	1.1	urmask = (1<<i) - 1;
38	gregl	2.4	urperm = (unsigned short )malloc((urmask+1)sizeof(unsigned short));
39	greg	1.1	if (urperm == NULL) {
40			eputs("out of memory in initurand\n");
41			quit(1);
42			}
43			urperm[0] = 0;
44			for (n = 1, offset = 1; n <= order; n++, offset <<= 1)
45			for (i = offset; i--; ) {
46			urperm[i] =
47			urperm[i+offset] = 2*urperm[i];
48			if (random() & 0x4000)
49			urperm[i]++;
50			else
51			urperm[i+offset]++;
52			}
53	gregl	2.3	return(1<<order);
54	greg	1.2	}
55
56
57			int
58	greg	1.3	ilhash(d, n) /* hash a set of integer values */
59	greg	1.2	register int *d;
60			register int n;
61			{
62			static int tab[8] = {13623,353,1637,5831,2314,3887,5832,8737};
63	greg	1.4	register int hval;
64	greg	1.2
65			hval = 0;
66			while (n-- > 0)
67			hval += d++ tab[n&7];
68	greg	1.3	return(hval);
69	greg	1.1	}