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RNG: added additional checks (which forced an interface redesign), updated comments

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This commit is contained in:
Mark Morschhäuser 2014-06-09 13:31:21 +02:00
parent 197dd0f3c8
commit ccab97ca7d
6 changed files with 65 additions and 26 deletions
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31
common/rng_sfmt.h
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@ -1,27 +1,28 @@
#ifndef RNG_SFMT_H
#define RNG_SFMT_H
#include <climits>
#include <QMutex>
#include "sfmt/SFMT.h"
#include "rng_abstract.h"
#include <QMutex>
/**
* This class represents the random number generator.
* Usage instructions:
* Create an instance of RNG_SFMT, then call getNumber(min, max).
* You should never call this function with min > max, this throws a
* std::invalid_argument exception. It is best practice to use getNumber() in a try block
* and catch the exception if min, max are entered by the user or computed somehow.
* This class encapsulates a state of the art PRNG and can be used
* to return uniformly distributed integer random numbers from a range [min, max].
* Though technically possible, min must be >= 0 and max should always be > 0.
* If max < 0 and min == 0 it is assumed that rand() % -max is wanted and the result will
* be -rand(0, -max).
* This is the only exception to the rule that !(min > max) and is actually unused in
* Cockatrice.
*
* Technical details:
* The RNG uses the SIMD-oriented Fast Mersenne Twister code v1.4.1 from
* http://www.math.sci.hiroshima-u.ac.jp/~%20m-mat/MT/SFMT/index.html
* To use this RNG, the class needs a sfmt_t structure for the RNG's internal state.
* It has to be initialized by sfmt_init_gen_rand() which is done in the constructor.
* The function sfmt_genrand_uint64() can then be used to create a 64 bit unsigned int
* pseudorandom number. This is done in getNumber().
* For more information see the author's website and look at the documentation and
* examples that are part of the official downloads.
* The SFMT RNG creates unsigned int 64bit pseudo random numbers.
*
* These are mapped to values from the interval [min, max] without bias by using Knuth's
* "Algorithm S (Selection sampling technique)" from "The Art of Computer Programming 3rd
* Edition Volume 2 / Seminumerical Algorithms".
*/
class RNG_SFMT : public RNG_Abstract {
@ -29,9 +30,11 @@ class RNG_SFMT : public RNG_Abstract {
private:
QMutex mutex;
sfmt_t sfmt;
// The discrete cumulative distribution function for the RNG
unsigned int cdf(unsigned int min, unsigned int max);
public:
RNG_SFMT(QObject *parent = 0);
unsigned int getNumber(unsigned int min, unsigned int max);
unsigned int rand(int min, int max);
};
#endif