src/common/urand.c

/* Copyright (c) 1998 Silicon Graphics, Inc. */

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

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

#include  "random.h"

#define  NULL           0

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

extern char  *malloc();

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((char *)urperm);
        size--;
        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:	2.4
Committed:	Mon Jan 5 16:47:37 1998 UTC (26 years, 3 months ago) by gregl
Content type:	text/plain
Branch:	MAIN
Changes since 2.3:	+6 -4 lines
Log Message:	added check for too many urand values
#	User	Rev	Content
1	gregl	2.4	/* Copyright (c) 1998 Silicon Graphics, Inc. */
2	greg	1.1
3			#ifndef lint
4	gregl	2.3	static char SCCSid[] = "$SunId$ SGI";
5	greg	1.1	#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	gregl	2.4	#define MAXORDER (8*sizeof(unsigned short))
16
17	greg	1.1	extern char *malloc();
18
19	gregl	2.4	unsigned short urperm = NULL; / urand() permutation */
20	greg	1.1	int urmask; /* bits used in permutation */
21
22
23	gregl	2.3	int
24	greg	1.1	initurand(size) /* initialize urand() for size entries */
25			int size;
26			{
27			int order, n;
28			register int i, offset;
29
30	greg	2.2	if (urperm != NULL)
31			free((char *)urperm);
32	greg	1.1	size--;
33			for (i = 1; size >>= 1; i++)
34			;
35	gregl	2.4	order = i>MAXORDER ? MAXORDER : i;
36	greg	1.1	urmask = (1<<i) - 1;
37	gregl	2.4	urperm = (unsigned short )malloc((urmask+1)sizeof(unsigned short));
38	greg	1.1	if (urperm == NULL) {
39			eputs("out of memory in initurand\n");
40			quit(1);
41			}
42			urperm[0] = 0;
43			for (n = 1, offset = 1; n <= order; n++, offset <<= 1)
44			for (i = offset; i--; ) {
45			urperm[i] =
46			urperm[i+offset] = 2*urperm[i];
47			if (random() & 0x4000)
48			urperm[i]++;
49			else
50			urperm[i+offset]++;
51			}
52	gregl	2.3	return(1<<order);
53	greg	1.2	}
54
55
56			int
57	greg	1.3	ilhash(d, n) /* hash a set of integer values */
58	greg	1.2	register int *d;
59			register int n;
60			{
61			static int tab[8] = {13623,353,1637,5831,2314,3887,5832,8737};
62	greg	1.4	register int hval;
63	greg	1.2
64			hval = 0;
65			while (n-- > 0)
66			hval += d++ tab[n&7];
67	greg	1.3	return(hval);
68	greg	1.1	}