spielwiese
Last change
on this file since 756676e was
756676e,
checked in by Reimer Behrends <behrends@…>, 5 years ago
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Add includes for globaldefs.2
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Property mode set to
100644
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File size:
1.2 KB
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1 | #include "misc/auxiliary.h" |
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2 | #include "sirandom.h" |
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3 | |
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4 | /*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*/ |
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5 | /* |
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6 | * |
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7 | * A prime modulus multiplicative linear congruential |
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8 | * generator (PMMLCG), or "Lehmer generator". |
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9 | * Implementation directly derived from the article: |
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10 | * |
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11 | * S. K. Park and K. W. Miller |
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12 | * Random Number Generators: Good Ones are Hard to Find |
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13 | * CACM vol 31, #10. Oct. 1988. pp 1192-1201. |
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14 | * |
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15 | * Using the following multiplier and modulus, we obtain a |
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16 | * generator which: |
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17 | * |
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18 | * 1) Has a full period: 1 to 2^31 - 2. |
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19 | * 2) Is testably "random" (see the article). |
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20 | * 3) Has a known implementation by E. L. Schrage. |
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21 | */ |
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22 | |
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23 | |
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24 | #define A 16807 /* A "good" multiplier */ |
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25 | #define M 2147483647 /* Modulus: 2^31 - 1 */ |
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26 | #define Q 127773 /* M / A */ |
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27 | #define R 2836 /* M % A */ |
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28 | |
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29 | |
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30 | VAR int siSeed = 1; |
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31 | |
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32 | int siRandNext(int r) |
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33 | { |
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34 | r = A * (r % Q) - R * (r / Q); |
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35 | |
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36 | if ( r < 0 ) |
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37 | r += M; |
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38 | |
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39 | return( r ); |
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40 | } |
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41 | |
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42 | int siRand() |
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43 | { |
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44 | siSeed=siRandNext(siSeed); |
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45 | return siSeed; |
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46 | } |
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47 | int siRandPlus1(int r) |
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48 | { |
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49 | return r+1; |
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50 | } |
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