src/common/urand.c

#ifndef lint
static const char       RCSid[] = "$Id: urand.c,v 2.7 2003/06/07 12:50:21 schorsch Exp $";
#endif
/*
 * Anticorrelated random function due to Christophe Schlick
 */

#include "copyright.h"

#include  <stdlib.h>

#include  "standard.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++)
                if (i == MAXORDER)
                        break;
        order = i;
        urmask = (1<<order) - 1;
        urperm = (unsigned short *)malloc((urmask+1)*sizeof(unsigned short));
        if (urperm == NULL) {
                eputs("out of memory in initurand\n");
                quit(1);
        }
        urperm[0] = (random() & 0x4000) != 0;
        for (n = 1, offset = 1; n <= order; n++, offset <<= 1)
                for (i = offset; i--; ) {
                        urperm[i+offset] = urperm[i] <<= 1;
                        if (random() & 0x4000)
                                urperm[i]++;
                        else
                                urperm[i+offset]++;
                }
        return(urmask+1);
}


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:	2.8
Committed:	Fri May 14 20:49:13 2004 UTC (19 years, 11 months ago) by greg
Content type:	text/plain
Branch:	MAIN
Changes since 2.7:	+9 -9 lines
Log Message:	Fixed bug in initialization of long random sequences
#	User	Rev	Content
1	greg	1.1	#ifndef lint
2	greg	2.8	static const char RCSid[] = "$Id: urand.c,v 2.7 2003/06/07 12:50:21 schorsch Exp $";
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	schorsch	2.7
12			#include "standard.h"
13	greg	1.1	#include "random.h"
14
15	greg	2.5	#undef initurand
16	greg	1.1
17	gregl	2.4	#define MAXORDER (8*sizeof(unsigned short))
18
19			unsigned short urperm = NULL; / urand() permutation */
20	greg	1.1	int urmask; /* bits used in permutation */
21
22	gregl	2.3	int
23	greg	1.1	initurand(size) /* initialize urand() for size entries */
24			int size;
25			{
26			int order, n;
27			register int i, offset;
28
29	greg	2.2	if (urperm != NULL)
30	greg	2.5	free((void *)urperm);
31			if (--size <= 0) {
32			urperm = NULL;
33			urmask = 0;
34			return(0);
35			}
36	greg	2.8	for (i = 1; (size >>= 1); i++)
37			if (i == MAXORDER)
38			break;
39			order = i;
40			urmask = (1<<order) - 1;
41	gregl	2.4	urperm = (unsigned short )malloc((urmask+1)sizeof(unsigned short));
42	greg	1.1	if (urperm == NULL) {
43			eputs("out of memory in initurand\n");
44			quit(1);
45			}
46	greg	2.8	urperm[0] = (random() & 0x4000) != 0;
47	greg	1.1	for (n = 1, offset = 1; n <= order; n++, offset <<= 1)
48			for (i = offset; i--; ) {
49	greg	2.8	urperm[i+offset] = urperm[i] <<= 1;
50	greg	1.1	if (random() & 0x4000)
51			urperm[i]++;
52			else
53			urperm[i+offset]++;
54			}
55	greg	2.8	return(urmask+1);
56	greg	1.2	}
57
58
59			int
60	greg	1.3	ilhash(d, n) /* hash a set of integer values */
61	greg	1.2	register int *d;
62			register int n;
63			{
64			static int tab[8] = {13623,353,1637,5831,2314,3887,5832,8737};
65	greg	1.4	register int hval;
66	greg	1.2
67			hval = 0;
68			while (n-- > 0)
69			hval += d++ tab[n&7];
70	greg	1.3	return(hval);
71	greg	1.1	}