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root/Development/ray/src/common/urand.c

Comparing ray/src/common/urand.c (file contents):
Revision 1.6 by greg, Thu Jul 11 16:25:58 1991 UTC vs.
Revision 2.6 by greg, Tue Feb 25 02:47:22 2003 UTC

#	Line 1 | Line 1
1	–	/* Copyright (c) 1991 Regents of the University of California */
2	–
1		#ifndef lint
2	<	static char SCCSid[] = "$SunId$ LBL";
2	>	static const char       RCSid[] = "$Id$";
3		#endif
6	–
4		/*
5		* Anticorrelated random function due to Christophe Schlick
6		*/
7
8	+	#include "copyright.h"
9	+
10	+	#include  <stdlib.h>
11		#include  "random.h"
12
13	<	#define  NULL           0
13	>	#undef initurand
14
15	<	extern char  *malloc();
15	>	#define  MAXORDER       (8*sizeof(unsigned short))
16
17	<	short  *urperm;         /* urand() permutation */
17	>	unsigned short  *urperm = NULL; /* urand() permutation */
18		int  urmask;            /* bits used in permutation */
19
20	<
20	>	int
21		initurand(size)         /* initialize urand() for size entries */
22		int  size;
23		{
24		int  order, n;
25		register int  i, offset;
26
27	<	size--;
27	>	if (urperm != NULL)
28	>	free((void *)urperm);
29	>	if (--size <= 0) {
30	>	urperm = NULL;
31	>	urmask = 0;
32	>	return(0);
33	>	}
34		for (i = 1; size >>= 1; i++)
35		;
36	<	order = i;
36	>	order = i>MAXORDER ? MAXORDER : i;
37		urmask = (1<<i) - 1;
38	<	urperm = (short *)malloc((urmask+1)*sizeof(short));
38	>	urperm = (unsigned short *)malloc((urmask+1)*sizeof(unsigned short));
39		if (urperm == NULL) {
40		eputs("out of memory in initurand\n");
41		quit(1);
#	Line 44 | Line 50 | int  size;
50		else
51		urperm[i+offset]++;
52		}
53	+	return(1<<order);
54		}
55
56
#	Line 59 | Line 66 | register int  n;
66		while (n-- > 0)
67		hval += *d++ * tab[n&7];
68		return(hval);
62	–	}
63	–
64	–
65	–	static char  bctab[256] = {
66	–	0, 1, 1, 2, 1, 2, 2, 3, 1, 2, 2, 3, 2, 3, 3, 4,
67	–	1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5,
68	–	1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5,
69	–	2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
70	–	1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5,
71	–	2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
72	–	2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
73	–	3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7,
74	–	1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5,
75	–	2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
76	–	2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
77	–	3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7,
78	–	2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
79	–	3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7,
80	–	3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7,
81	–	4, 5, 5, 6, 5, 6, 6, 7, 5, 6, 6, 7, 6, 7, 7, 8,
82	–	};
83	–
84	–
85	–	#define NBITS           32
86	–
87	–	#if NBITS==32
88	–	#define  bitcount(i)    (bctab[(i)>>24&0xff]+bctab[(i)>>16&0xff]+ \
89	–	bctab[(i)>>8&0xff]+bctab[(i)&0xff])
90	–	#endif
91	–	#if  NBITS==16
92	–	#define  bitcount(i)    (bctab[(i)>>8&0xff]+bctab[(i)&0xff])
93	–	#endif
94	–
95	–
96	–	int
97	–	urind(s, i)                     /* compute i'th index from seed s */
98	–	int     s, i;
99	–	{
100	–	register int  ss, k;
101	–	int  left;
102	–
103	–	ss = s*1103515245 + 12345;
104	–	left = 0;
105	–	for (k = i/NBITS; k--; ) {
106	–	left += bitcount(ss);
107	–	ss = ss*1103515245 + 12345;
108	–	}
109	–	for (k = i&(NBITS-1); k--; ss >>= 1)
110	–	left += ss & 1;
111	–	if (ss & 1)
112	–	return(s-left-1);
113	–	return(s-left+i);
69		}

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