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greg |
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#ifndef lint |
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greg |
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static const char RCSid[] = "$Id$"; |
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greg |
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#endif |
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/* |
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* Compute pseudo-asyncronous entry point for urand(3) |
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greg |
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*/ |
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/* ==================================================================== |
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* The Radiance Software License, Version 1.0 |
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* |
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* Copyright (c) 1990 - 2002 The Regents of the University of California, |
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* through Lawrence Berkeley National Laboratory. All rights reserved. |
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* |
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* Redistribution and use in source and binary forms, with or without |
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* modification, are permitted provided that the following conditions |
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* are met: |
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* |
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* 1. Redistributions of source code must retain the above copyright |
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* notice, this list of conditions and the following disclaimer. |
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* |
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* 2. Redistributions in binary form must reproduce the above copyright |
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* notice, this list of conditions and the following disclaimer in |
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* the documentation and/or other materials provided with the |
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* distribution. |
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* |
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* 3. The end-user documentation included with the redistribution, |
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* if any, must include the following acknowledgment: |
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* "This product includes Radiance software |
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* (http://radsite.lbl.gov/) |
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* developed by the Lawrence Berkeley National Laboratory |
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* (http://www.lbl.gov/)." |
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* Alternately, this acknowledgment may appear in the software itself, |
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* if and wherever such third-party acknowledgments normally appear. |
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* |
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* 4. The names "Radiance," "Lawrence Berkeley National Laboratory" |
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* and "The Regents of the University of California" must |
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* not be used to endorse or promote products derived from this |
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* software without prior written permission. For written |
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* permission, please contact [email protected]. |
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* |
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* 5. Products derived from this software may not be called "Radiance", |
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* nor may "Radiance" appear in their name, without prior written |
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* permission of Lawrence Berkeley National Laboratory. |
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* |
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* THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED |
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* WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES |
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* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE |
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* DISCLAIMED. IN NO EVENT SHALL Lawrence Berkeley National Laboratory OR |
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* ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, |
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* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT |
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* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF |
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* USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND |
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* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, |
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* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT |
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* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF |
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* SUCH DAMAGE. |
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* ==================================================================== |
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* |
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* This software consists of voluntary contributions made by many |
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* individuals on behalf of Lawrence Berkeley National Laboratory. For more |
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* information on Lawrence Berkeley National Laboratory, please see |
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* <http://www.lbl.gov/>. |
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greg |
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*/ |
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#define NBITS 32 /* number of bits in an integer */ |
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static char bctab[256] = { |
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0, 1, 1, 2, 1, 2, 2, 3, 1, 2, 2, 3, 2, 3, 3, 4, |
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1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5, |
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1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5, |
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2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6, |
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1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5, |
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2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6, |
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2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6, |
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3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7, |
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1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5, |
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2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6, |
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2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6, |
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3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7, |
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2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6, |
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3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7, |
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3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7, |
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4, 5, 5, 6, 5, 6, 6, 7, 5, 6, 6, 7, 6, 7, 7, 8, |
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}; |
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#if NBITS==32 |
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#define bitcount(i) (bctab[(i)>>24&0xff]+bctab[(i)>>16&0xff]+ \ |
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bctab[(i)>>8&0xff]+bctab[(i)&0xff]) |
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#endif |
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#if NBITS==16 |
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#define bitcount(i) (bctab[(i)>>8&0xff]+bctab[(i)&0xff]) |
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#endif |
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int |
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urind(s, i) /* compute i'th index from seed s */ |
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int s, i; |
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{ |
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register int ss, k; |
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int left; |
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ss = s*1103515245 + 12345; |
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left = 0; |
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for (k = i/NBITS; k--; ) { |
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left += bitcount(ss); |
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ss = ss*1103515245 + 12345; |
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} |
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for (k = i&(NBITS-1); k--; ss >>= 1) |
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left += ss & 1; |
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if (ss & 1) |
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return(s-left-1); |
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return(s-left+i); |
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} |
