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/* $Id$ */
/** @file random_func.h */
#ifndef RANDOM_FUNC_HPP
#define RANDOM_FUNC_HPP
/**************
* Warning: DO NOT enable this unless you understand what it does
*
* If enabled, in a network game all randoms will be dumped to the
* stdout if the first client joins (or if you are a client). This
* is to help finding desync problems.
*
* Warning: DO NOT enable this unless you understand what it does
**************/
//#define RANDOM_DEBUG
// Enable this to produce higher quality random numbers.
// Doesn't work with network yet.
// #define MERSENNE_TWISTER
void SetRandomSeed(uint32 seed);
#ifdef RANDOM_DEBUG
#define Random() DoRandom(__LINE__, __FILE__)
uint32 DoRandom(int line, const char *file);
#define RandomRange(max) DoRandomRange(max, __LINE__, __FILE__)
uint DoRandomRange(uint max, int line, const char *file);
#else
uint32 Random();
uint RandomRange(uint max);
#endif
uint32 InteractiveRandom(); // Used for random sequences that are not the same on the other end of the multiplayer link
uint InteractiveRandomRange(uint max);
/**
* Checks if a given randomize-number is below a given probability.
*
* This function is used to check if the given probability by the fraction of (a/b)
* is greater than low 16 bits of the given randomize-number v.
*
* Do not use this function twice on the same random 16 bits as it will yield
* the same result. One can use a random number for two calls to Chance16I,
* where one call sends the low 16 bits and the other the high 16 bits.
*
* @param a The numerator of the fraction
* @param b The denominator of the fraction, must of course not be null
* @param r The given randomize-number
* @return True if v is less or equals (a/b)
*/
static inline bool Chance16I(const uint a, const uint b, const uint32 r)
{
assert(b != 0);
return (uint16)r < (uint16)((a << 16) / b);
}
/**
* Flips a coin with a given probability.
*
* This macro can be used to get true or false randomized according to a
* given probability. The parameter a and b create a percent value with
* (a/b). The macro returns true in (a/b) percent.
*
* @see Chance16I()
* @param a The numerator of the fraction
* @param b The denominator of the fraction
* @return True in (a/b) percent
*/
static inline bool Chance16(const uint a, const uint b)
{
return Chance16I(a, b, Random());
}
/**
* Flips a coin with a given probability and saves the randomize-number in a variable.
*
* This function uses the same parameters as Chance16. The third parameter
* must be a variable the randomize-number from Random() is saved in.
*
* The low 16 bits of r will already be used and can therefor not be passed to
* Chance16I. One can only send the high 16 bits to Chance16I.
*
* @see Chance16I()
* @param a The numerator of the fraction
* @param b The denominator of the fraction
* @param r The variable to save the randomize-number from Random()
* @return True in (a/b) percent
*/
static inline bool Chance16R(const uint a, const uint b, uint32 &r)
{
r = Random();
return Chance16I(a, b, r);
}
#endif /* RANDOM_FUNC_HPP */
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