63 lines
1.4 KiB
C
Executable file
63 lines
1.4 KiB
C
Executable file
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/*
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utl_random
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A "32-bit Multiply with carry" random number generator.
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*/
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#include "utl_random.h"
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/* Initialize random number generator with two integer variables */
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void utl_randomInit(RND_CTX * rndContext, unsigned int xi, unsigned int ci)
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{
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/*
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* Choose a value for 'a' from this list
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* 1791398085 1929682203 1683268614 1965537969 1675393560
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* 1967773755 1517746329 1447497129 1655692410 1606218150
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* 2051013963 1075433238 1557985959 1781943330 1893513180
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* 1631296680 2131995753 2083801278 1873196400 1554115554
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*/
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rndContext->a = 1655692410;
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rndContext->x = 30903;
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rndContext->c = 0;
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if (xi != 0)
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rndContext->x = xi;
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rndContext->c = ci;
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rndContext->ah = rndContext->a >> 16;
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rndContext->al = rndContext->a & 65535;
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}
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/* Initialize random number generator from time */
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void utl_randomInitTime(RND_CTX * rndContext)
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{
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int a,b;
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srand(time(NULL));
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a=rand();
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srand(clock());
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b=rand();
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utl_randomInit(rndContext, a, b);
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}
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/* Returns random numbers */
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unsigned int utl_random(RND_CTX * rndContext)
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{
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unsigned int xh, xl;
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xh = rndContext->x >> 16, xl = rndContext->x & 65535;
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rndContext->x = rndContext->x * rndContext->a + rndContext->c;
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rndContext->c =
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xh * rndContext->ah + ((xh * rndContext->al) >> 16) +
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((xl * rndContext->ah) >> 16);
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if (xl * rndContext->al >= (~rndContext->c + 1))
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rndContext->c++;
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return (rndContext->x);
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}
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