39

/**

    40

 * Checks if a given randomize-number is below a given probability.

    41

 *

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 * This function is used to check if the given probability by the fraction of (a/b)

    43

 * is greater than low 16 bits of the given randomize-number v.

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 *

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 * Do not use this function twice on the same random 16 bits as it will yield

    46

 * the same result. One can use a random number for two calls to Chance16I,

    47

 * where one call sends the low 16 bits and the other the high 16 bits.

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 *

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 * @param a The numerator of the fraction

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 * @param b The denominator of the fraction, must of course not be null

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 * @param r The given randomize-number

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 * @return True if v is less or equals (a/b)

    53

 */

    54

static inline bool Chance16I(const uint a, const uint b, const uint32 r)

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{

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	assert(b != 0);

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	return (uint16)r < (uint16)((a << 16) / b);

    58

}

    59

    60

/**

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 * Flips a coin with a given probability.

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 *

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 * This macro can be used to get true or false randomized according to a

    64

 * given probability. The parameter a and b create a percent value with

    65

 * (a/b). The macro returns true in (a/b) percent.

    66

 *

    67

 * @see Chance16I()

    68

 * @param a The numerator of the fraction

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 * @param b The denominator of the fraction

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 * @return True in (a/b) percent

    71

 */

    72

static inline bool Chance16(const uint a, const uint b)

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{

    74

	return Chance16I(a, b, Random());

    75

}

    76

    77

/**

    78

 * Flips a coin with a given probability and saves the randomize-number in a variable.

    79

 *

    80

 * This function uses the same parameters as Chance16. The third parameter

    81

 * must be a variable the randomize-number from Random() is saved in.

    82

 *

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 * The low 16 bits of r will already be used and can therefor not be passed to

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 * Chance16I. One can only send the high 16 bits to Chance16I.

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 *

    86

 * @see Chance16I()

    87

 * @param a The numerator of the fraction

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 * @param b The denominator of the fraction

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 * @param r The variable to save the randomize-number from Random()

    90

 * @return True in (a/b) percent

    91

 */

    92

static inline bool Chance16R(const uint a, const uint b, uint32 &r)

    93

{

    94

	r = Random();

    95

	return Chance16I(a, b, r);

    96

}

    97