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34 lines
519 B
C++
34 lines
519 B
C++
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#include "lcg.h"
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/* Dead simple 8-bit Linear Congruential Generator (PRNG).
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*
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* An LCG is defined as
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*
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* X(n+1) = ( a * X(n) + c ) % m
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*
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* In this implementation:
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* a = 2^7 = 128
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* c = 251
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* m = 256
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*
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* Like all LCGs, the low-order bits of this cycle quickly. The
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* high-order bits have better (longer) periods.
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*/
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LCG::LCG(uint16_t s)
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{
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seed = s;
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}
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void LCG::srnd(uint16_t s)
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{
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seed = s;
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}
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uint8_t LCG::rnd()
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{
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seed = (seed << 7) - seed + 251;
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return (uint8_t)(seed + (seed>>8));
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}
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