src/common/urand.c

/* Copyright (c) 1992 Regents of the University of California */

#ifndef lint
static char SCCSid[] = "$SunId$ LBL";
#endif

/*
 * Anticorrelated random function due to Christophe Schlick
 */

#include  "random.h"

#define  NULL           0

extern char  *malloc();

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


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

        if (urperm != NULL)
                free((char *)urperm);
        size--;
        for (i = 1; size >>= 1; i++)
                ;
        order = i;
        urmask = (1<<i) - 1;
        urperm = (short *)malloc((urmask+1)*sizeof(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]++;
                }
}


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:	2.2
Committed:	Sat Sep 5 13:40:55 1992 UTC (31 years, 8 months ago) by greg
Content type:	text/plain
Branch:	MAIN
Changes since 2.1:	+4 -2 lines
Log Message:	added free call for multiple calls to initurand()
#	User	Rev	Content
1	greg	2.2	/* Copyright (c) 1992 Regents of the University of California */
2	greg	1.1
3			#ifndef lint
4			static char SCCSid[] = "$SunId$ LBL";
5			#endif
6
7			/*
8	greg	1.5	* Anticorrelated random function due to Christophe Schlick
9	greg	1.1	*/
10
11			#include "random.h"
12
13			#define NULL 0
14
15			extern char *malloc();
16
17	greg	2.2	short urperm = NULL; / urand() permutation */
18	greg	1.1	int urmask; /* bits used in permutation */
19
20
21			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			free((char *)urperm);
29	greg	1.1	size--;
30			for (i = 1; size >>= 1; i++)
31			;
32			order = i;
33			urmask = (1<<i) - 1;
34			urperm = (short )malloc((urmask+1)sizeof(short));
35			if (urperm == NULL) {
36			eputs("out of memory in initurand\n");
37			quit(1);
38			}
39			urperm[0] = 0;
40			for (n = 1, offset = 1; n <= order; n++, offset <<= 1)
41			for (i = offset; i--; ) {
42			urperm[i] =
43			urperm[i+offset] = 2*urperm[i];
44			if (random() & 0x4000)
45			urperm[i]++;
46			else
47			urperm[i+offset]++;
48			}
49	greg	1.2	}
50
51
52			int
53	greg	1.3	ilhash(d, n) /* hash a set of integer values */
54	greg	1.2	register int *d;
55			register int n;
56			{
57			static int tab[8] = {13623,353,1637,5831,2314,3887,5832,8737};
58	greg	1.4	register int hval;
59	greg	1.2
60			hval = 0;
61			while (n-- > 0)
62			hval += d++ tab[n&7];
63	greg	1.3	return(hval);
64	greg	1.1	}