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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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#endif
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/*
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* Uncorrelated (anticorrelated) random function
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*/
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#include "random.h"
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#define NULL 0
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extern char *malloc();
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short *urperm; /* urand() permutation */
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int urmask; /* bits used in permutation */
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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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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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if (urperm == NULL) {
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eputs("out of memory in initurand\n");
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quit(1);
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}
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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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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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}
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