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37 lines
1004 B
Plaintext
37 lines
1004 B
Plaintext
1File: rand.c Page 1
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1 /* rand.c - kluges a random number generator with addition & overflow */
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2 #include <portab.h>
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3
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4
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5 #define NSEEDS 7
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6
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7 MLOCAL UWORD _seeds[NSEEDS] =
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8 { 0, 24213, 12345, 4622, 2143, 32010, 7942 };
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9
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10 MLOCAL WORD _seedptr=0;
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11
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12
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13 WORD srand(seed1)
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14 int seed1;
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15 {
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16 WORD ncs;
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17 _seeds[0] = seed1;
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18 for( ncs = seed1&077; ncs; ncs-- )
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19 rand();
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20 return(rand());
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21 }
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22
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23
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24 WORD rand()
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25 {
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26 UWORD tot, ii;
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27
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28 for( tot=0, ii=0; ii<NSEEDS; ii++)
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29 tot += _seeds[ii]; /* ignore overflow */
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30 if( ++_seedptr >= NSEEDS )
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31 _seedptr = 0;
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32 _seeds[_seedptr] = tot;
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33 return( tot >> 1 ); /* ignore lo bit because of addition */
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34 }
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35
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