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/* Copyright (c) 1991 Regents of the University of California */ |
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#ifndef lint |
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static char SCCSid[] = "$SunId$ LBL"; |
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static const char RCSid[] = "$Id$"; |
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#endif |
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/* |
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* Anticorrelated random function due to Christophe Schlick |
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*/ |
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#include "copyright.h" |
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#include <stdlib.h> |
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#include "standard.h" |
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#include "random.h" |
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#define NULL 0 |
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#undef initurand |
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extern char *malloc(); |
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#define MAXORDER (8*sizeof(unsigned short)) |
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short *urperm; /* urand() permutation */ |
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int urmask; /* bits used in permutation */ |
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static unsigned short empty_tab = 0; |
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unsigned short *urperm = &empty_tab; /* urand() permutation */ |
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int urmask = 0; /* bits used in permutation */ |
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int |
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initurand(size) /* initialize urand() for size entries */ |
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int size; |
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{ |
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int order, n; |
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register int i, offset; |
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size--; |
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for (i = 1; size >>= 1; i++) |
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; |
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if ((urperm != NULL) & (urperm != &empty_tab)) |
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free((void *)urperm); |
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if (--size <= 0) { |
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empty_tab = 0; |
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urperm = &empty_tab; |
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urmask = 0; |
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return(0); |
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} |
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for (i = 1; (size >>= 1); i++) |
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if (i == MAXORDER) |
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break; |
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order = i; |
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urmask = (1<<i) - 1; |
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urperm = (short *)malloc((urmask+1)*sizeof(short)); |
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urmask = (1<<order) - 1; |
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urperm = (unsigned short *)malloc((urmask+1)*sizeof(unsigned short)); |
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if (urperm == NULL) { |
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eputs("out of memory in initurand\n"); |
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quit(1); |
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urperm[0] = 0; |
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for (n = 1, offset = 1; n <= order; n++, offset <<= 1) |
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for (i = offset; i--; ) { |
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urperm[i] = |
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urperm[i+offset] = 2*urperm[i]; |
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urperm[i+offset] = urperm[i] <<= 1; |
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if (random() & 0x4000) |
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urperm[i]++; |
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else |
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urperm[i+offset]++; |
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} |
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return(urmask+1); |
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} |
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register int *d; |
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register int n; |
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{ |
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static int tab[8] = {13623,353,1637,5831,2314,3887,5832,8737}; |
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static int tab[8] = {103699,96289,73771,65203,81119,87037,92051,98899}; |
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register int hval; |
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hval = 0; |
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while (n-- > 0) |
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hval += *d++ * tab[n&7]; |
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return(hval); |
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} |
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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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#define NBITS 32 |
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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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hval ^= *d++ * tab[n&7]; |
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return(hval & 0x7fffffff); |
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} |
