src/common/urand.c

/* Copyright (c) 1991 Regents of the University of California */

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

/*
 * Uncorrelated (anticorrelated) random function
 */

#include  "random.h"

#define  NULL           0

extern char  *malloc();

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


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

        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:	1.4
Committed:	Fri Jun 7 10:47:17 1991 UTC (34 years, 5 months ago) by greg
Content type:	text/plain
Branch:	MAIN
Changes since 1.3:	+1 -1 lines
Log Message:	changed definition of hval for consistency in ilhash()
#	User	Rev	Content
1	greg	1.1	/* Copyright (c) 1991 Regents of the University of California */
2
3			#ifndef lint
4			static char SCCSid[] = "$SunId$ LBL";
5			#endif
6
7			/*
8			* Uncorrelated (anticorrelated) random function
9			*/
10
11			#include "random.h"
12
13			#define NULL 0
14
15			extern char *malloc();
16
17			short urperm; / urand() permutation */
18			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			size--;
28			for (i = 1; size >>= 1; i++)
29			;
30			order = i;
31			urmask = (1<<i) - 1;
32			urperm = (short )malloc((urmask+1)sizeof(short));
33			if (urperm == NULL) {
34			eputs("out of memory in initurand\n");
35			quit(1);
36			}
37			urperm[0] = 0;
38			for (n = 1, offset = 1; n <= order; n++, offset <<= 1)
39			for (i = offset; i--; ) {
40			urperm[i] =
41			urperm[i+offset] = 2*urperm[i];
42			if (random() & 0x4000)
43			urperm[i]++;
44			else
45			urperm[i+offset]++;
46			}
47	greg	1.2	}
48
49
50			int
51	greg	1.3	ilhash(d, n) /* hash a set of integer values */
52	greg	1.2	register int *d;
53			register int n;
54			{
55			static int tab[8] = {13623,353,1637,5831,2314,3887,5832,8737};
56	greg	1.4	register int hval;
57	greg	1.2
58			hval = 0;
59			while (n-- > 0)
60			hval += d++ tab[n&7];
61	greg	1.3	return(hval);
62	greg	1.1	}