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root/radiance/ray/src/common/urand.c
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Comparing ray/src/common/urand.c (file contents):
Revision 2.7 by schorsch, Sat Jun 7 12:50:21 2003 UTC vs.
Revision 2.10 by greg, Wed Apr 5 06:22:56 2006 UTC

# Line 16 | Line 16 | static const char      RCSid[] = "$Id$";
16  
17   #define  MAXORDER       (8*sizeof(unsigned short))
18  
19 < unsigned short  *urperm = NULL; /* urand() permutation */
20 < int  urmask;            /* bits used in permutation */
19 > static unsigned short  empty_tab = 0;
20  
21 + unsigned short  *urperm = &empty_tab;   /* urand() permutation */
22 + int  urmask = 0;                        /* bits used in permutation */
23 +
24   int
25   initurand(size)         /* initialize urand() for size entries */
26   int  size;
# Line 26 | Line 28 | int  size;
28          int  order, n;
29          register int  i, offset;
30  
31 <        if (urperm != NULL)
31 >        if ((urperm != NULL) & (urperm != &empty_tab))
32                  free((void *)urperm);
33          if (--size <= 0) {
34 <                urperm = NULL;
34 >                empty_tab = 0;
35 >                urperm = &empty_tab;
36                  urmask = 0;
37                  return(0);
38          }
39 <        for (i = 1; size >>= 1; i++)
40 <                ;
41 <        order = i>MAXORDER ? MAXORDER : i;
42 <        urmask = (1<<i) - 1;
39 >        for (i = 1; (size >>= 1); i++)
40 >                if (i == MAXORDER)
41 >                        break;
42 >        order = i;
43 >        urmask = (1<<order) - 1;
44          urperm = (unsigned short *)malloc((urmask+1)*sizeof(unsigned short));
45          if (urperm == NULL) {
46                  eputs("out of memory in initurand\n");
# Line 45 | Line 49 | int  size;
49          urperm[0] = 0;
50          for (n = 1, offset = 1; n <= order; n++, offset <<= 1)
51                  for (i = offset; i--; ) {
52 <                        urperm[i] =
49 <                        urperm[i+offset] = 2*urperm[i];
52 >                        urperm[i+offset] = urperm[i] <<= 1;
53                          if (random() & 0x4000)
54                                  urperm[i]++;
55                          else
56                                  urperm[i+offset]++;
57                  }
58 <        return(1<<order);
58 >        return(urmask+1);
59   }
60  
61  
# Line 61 | Line 64 | ilhash(d, n)                   /* hash a set of integer values */
64   register int  *d;
65   register int  n;
66   {
67 <        static int  tab[8] = {13623,353,1637,5831,2314,3887,5832,8737};
67 >        static int  tab[8] = {103699,96289,73771,65203,81119,87037,92051,98899};
68          register int  hval;
69  
70          hval = 0;
71          while (n-- > 0)
72 <                hval += *d++ * tab[n&7];
73 <        return(hval);
72 >                hval ^= *d++ * tab[n&7];
73 >        return(hval & 0x7fffffff);
74   }

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