src/common/urind.c

#ifndef lint
static const char       RCSid[] = "$Id$";
#endif
/*
 * Compute pseudo-asyncronous entry point for urand(3)
 */

/* ====================================================================
 * The Radiance Software License, Version 1.0
 *
 * Copyright (c) 1990 - 2002 The Regents of the University of California,
 * through Lawrence Berkeley National Laboratory.   All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *         notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *       notice, this list of conditions and the following disclaimer in
 *       the documentation and/or other materials provided with the
 *       distribution.
 *
 * 3. The end-user documentation included with the redistribution,
 *           if any, must include the following acknowledgment:
 *             "This product includes Radiance software
 *                 (http://radsite.lbl.gov/)
 *                 developed by the Lawrence Berkeley National Laboratory
 *               (http://www.lbl.gov/)."
 *       Alternately, this acknowledgment may appear in the software itself,
 *       if and wherever such third-party acknowledgments normally appear.
 *
 * 4. The names "Radiance," "Lawrence Berkeley National Laboratory"
 *       and "The Regents of the University of California" must
 *       not be used to endorse or promote products derived from this
 *       software without prior written permission. For written
 *       permission, please contact [email protected].
 *
 * 5. Products derived from this software may not be called "Radiance",
 *       nor may "Radiance" appear in their name, without prior written
 *       permission of Lawrence Berkeley National Laboratory.
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED.   IN NO EVENT SHALL Lawrence Berkeley National Laboratory OR
 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of Lawrence Berkeley National Laboratory.   For more
 * information on Lawrence Berkeley National Laboratory, please see
 * <http://www.lbl.gov/>.
 */

#define NBITS           32              /* number of bits in an integer */

static char  bctab[256] = {
                0, 1, 1, 2, 1, 2, 2, 3, 1, 2, 2, 3, 2, 3, 3, 4,
                1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5,
                1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5,
                2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
                1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5,
                2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
                2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
                3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7,
                1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5,
                2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
                2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
                3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7,
                2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
                3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7,
                3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7,
                4, 5, 5, 6, 5, 6, 6, 7, 5, 6, 6, 7, 6, 7, 7, 8,
        };

#if NBITS==32
#define  bitcount(i)    (bctab[(i)>>24&0xff]+bctab[(i)>>16&0xff]+ \
                                bctab[(i)>>8&0xff]+bctab[(i)&0xff])
#endif
#if  NBITS==16
#define  bitcount(i)    (bctab[(i)>>8&0xff]+bctab[(i)&0xff])
#endif


int
urind(s, i)                     /* compute i'th index from seed s */
int     s, i;
{
        register int  ss, k;
        int  left;

        ss = s*1103515245 + 12345;
        left = 0;
        for (k = i/NBITS; k--; ) {
                left += bitcount(ss);
                ss = ss*1103515245 + 12345;
        }
        for (k = i&(NBITS-1); k--; ss >>= 1)
                left += ss & 1;
        if (ss & 1)
                return(s-left-1);
        return(s-left+i);
}
Revision:	2.2
Committed:	Sat Feb 22 02:07:22 2003 UTC (21 years, 2 months ago) by greg
Content type:	text/plain
Branch:	MAIN
Changes since 2.1:	+58 -4 lines
Log Message:	Changes and check-in for 3.5 release Includes new source files and modifications not recorded for many years See ray/doc/notes/ReleaseNotes for notes between 3.1 and 3.5 release
#	Content
1	#ifndef lint
2	static const char RCSid[] = "$Id$";
3	#endif
4	/*
5	* Compute pseudo-asyncronous entry point for urand(3)
6	*/
7
8	/* ====================================================================
9	* The Radiance Software License, Version 1.0
10	*
11	* Copyright (c) 1990 - 2002 The Regents of the University of California,
12	* through Lawrence Berkeley National Laboratory. All rights reserved.
13	*
14	* Redistribution and use in source and binary forms, with or without
15	* modification, are permitted provided that the following conditions
16	* are met:
17	*
18	* 1. Redistributions of source code must retain the above copyright
19	* notice, this list of conditions and the following disclaimer.
20	*
21	* 2. Redistributions in binary form must reproduce the above copyright
22	* notice, this list of conditions and the following disclaimer in
23	* the documentation and/or other materials provided with the
24	* distribution.
25	*
26	* 3. The end-user documentation included with the redistribution,
27	* if any, must include the following acknowledgment:
28	* "This product includes Radiance software
29	* (http://radsite.lbl.gov/)
30	* developed by the Lawrence Berkeley National Laboratory
31	* (http://www.lbl.gov/)."
32	* Alternately, this acknowledgment may appear in the software itself,
33	* if and wherever such third-party acknowledgments normally appear.
34	*
35	* 4. The names "Radiance," "Lawrence Berkeley National Laboratory"
36	* and "The Regents of the University of California" must
37	* not be used to endorse or promote products derived from this
38	* software without prior written permission. For written
39	* permission, please contact [email protected].
40	*
41	* 5. Products derived from this software may not be called "Radiance",
42	* nor may "Radiance" appear in their name, without prior written
43	* permission of Lawrence Berkeley National Laboratory.
44	*
45	* THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
46	* WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
47	* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
48	* DISCLAIMED. IN NO EVENT SHALL Lawrence Berkeley National Laboratory OR
49	* ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
50	* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
51	* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
52	* USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
53	* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
54	* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
55	* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
56	* SUCH DAMAGE.
57	* ====================================================================
58	*
59	* This software consists of voluntary contributions made by many
60	* individuals on behalf of Lawrence Berkeley National Laboratory. For more
61	* information on Lawrence Berkeley National Laboratory, please see
62	* <http://www.lbl.gov/>.
63	*/
64
65	#define NBITS 32 /* number of bits in an integer */
66
67	static char bctab[256] = {
68	0, 1, 1, 2, 1, 2, 2, 3, 1, 2, 2, 3, 2, 3, 3, 4,
69	1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5,
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	1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5,
73	2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
74	2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
75	3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7,
76	1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5,
77	2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
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	2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
81	3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7,
82	3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7,
83	4, 5, 5, 6, 5, 6, 6, 7, 5, 6, 6, 7, 6, 7, 7, 8,
84	};
85
86	#if NBITS==32
87	#define bitcount(i) (bctab[(i)>>24&0xff]+bctab[(i)>>16&0xff]+ \
88	bctab[(i)>>8&0xff]+bctab[(i)&0xff])
89	#endif
90	#if NBITS==16
91	#define bitcount(i) (bctab[(i)>>8&0xff]+bctab[(i)&0xff])
92	#endif
93
94
95	int
96	urind(s, i) /* compute i'th index from seed s */
97	int s, i;
98	{
99	register int ss, k;
100	int left;
101
102	ss = s*1103515245 + 12345;
103	left = 0;
104	for (k = i/NBITS; k--; ) {
105	left += bitcount(ss);
106	ss = ss*1103515245 + 12345;
107	}
108	for (k = i&(NBITS-1); k--; ss >>= 1)
109	left += ss & 1;
110	if (ss & 1)
111	return(s-left-1);
112	return(s-left+i);
113	}