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用于多个实例的C++ Boost随机数生成器集合

boost random c++

Cyrillm_44 · 技术社区 · 8 年前

我想创建一个类的许多实例,并希望它们使用boost随机数生成器以用户定义的平均值进行正态分布跳转。我从一些来源读到他们说你不想像 here . 理想情况下,我需要一个全局生成器,并且每个类的实例都有能力更改平均值,并生成一个随机数,这对所有实例都不一样。我正在努力实现这一点,我有一个全局标准类,但该类的每个实例的种子都是相同的。

// C/C++ standard library
#include <iostream>
#include <cstdlib>
#include <ctime>

#include <boost/random/mersenne_twister.hpp>
#include <boost/random/variate_generator.hpp>
#include <boost/random/lognormal_distribution.hpp>

/**
 * The mt11213b generator is fast and has a reasonable cycle length
 * See http://www.boost.org/doc/libs/1_60_0/doc/html/boost_random/reference.html#boost_random.reference.generators
 */
struct random_generator : boost::mt11213b {
    random_generator(void){
        seed(static_cast<unsigned int>(std::time(0)));
    }
} random_generator;


template<
    class Type
> struct Distribution {
    Type distribution;
    boost::variate_generator<decltype(random_generator),Type> variate_generator;

    template<class... Args>
    Distribution(Args... args):
        variate_generator(random_generator,Type(args...)) {}

    double random(void) {
        return variate_generator();
    }
};
typedef Distribution< boost::normal_distribution<> > Normal;

using namespace std;
// global normal random number generator
Normal normal_random_generator;

// Class Individual
class Individual {
    public:
        Individual() { } // constructor initialise value
        virtual~Individual() = default;
        // an accessor to pass information back
        void move_bias_random_walk(double mu) {
            normal_random_generator = {mu, sigma_};
            distance_ += normal_random_generator.random();
        }

        // An accessor for the distance object
        double get_distance() {
            return distance_;
        }

    private:
        //containers
        double distance_ = 0.4;
        double sigma_ = 0.4;
};


int main() {
    cout << "!!!Begin!!!" << endl;
    // Initialise two individuals in this case but there could be thousands
    Individual individual_a;
    Individual individual_b;

    cout << "starting values: individual a = " << individual_a.get_distance() << " individual b = " << individual_b.get_distance() << endl;
    // Do 10 jumps with the same mean for each individual and see where they end up each time

    cout << "A\tB" << endl;
    for (auto i = 1; i <= 10; ++i) {
        double mean = rand();
        individual_a.move_bias_random_walk(mean);
        individual_b.move_bias_random_walk(mean);
        cout << individual_a.get_distance() << "\t" << individual_b.get_distance() << endl;
    }
    cout << "finished" << endl;

    system("PAUSE");
    return 0;
}

这是编译上述代码得到的输出。

!!!Begin!!!
starting values: individual a = 0.4 individual b = 0.4
A   B
41.8024 41.8024
18509.2 18509.2
24843.6 24843.6
51344   51344
70513.4 70513.4
86237.8 86237.8
97716.2 97716.2
127075  127075
154037  154037
178501  178501
finished

2 回复 | 直到 8 年前

sehe 8 年前

正如christoph所评论的,如果复制生成器引擎的状态,将有两个状态相同的引擎。

因此,在复制之后为引擎设定种子:

template<class... Args>
Distribution(Args... args):
    variate_generator(random_generator,Type(args...)) {
        boost::random::random_device dev;
        variate_generator.engine().seed(dev);
    }

注意种子是如何从 random_device 是非常可取的。这可以确保种子本身是随机的,并且引擎的整个状态都是种子。

如果不想链接到Boost Random,可以再次使用单个种子值:

template<class... Args>
Distribution(Args... args):
    variate_generator(random_generator,Type(args...)) {
        std::random_device dev;
        variate_generator.engine().seed(dev());
    }

其他问题

当你这样做的时候

normal_random_generator = {mu, sigma_};

你要替换你的全球 Distribution 实例和设置 mu 你从梅因得到的价值。因为你(AB)使用 rand() 在那里, 穆 只是一些完全不随机的较大值。在我的系统里

与此相比,您的分布的sigma很小,因此生成的值将接近原始值,数字的科学格式将隐藏任何差异:

!!!Begin!!!
starting values: individual a = 0.4 individual b = 0.4
A       B
1.80429e+09     1.80429e+09
2.65122e+09     2.65122e+09
4.33291e+09     4.33291e+09
6.04755e+09     6.04755e+09
8.0053e+09      8.0053e+09
8.42954e+09     8.42954e+09
9.14942e+09     9.14942e+09
1.07992e+10     1.07992e+10
1.13957e+10     1.13957e+10
1.25853e+10     1.25853e+10
finished

看起来两列的值都一样。不过,它们基本上只是 RAND() 变化很小。添加

std::cout << std::fixed;

表明存在差异:

!!!Begin!!!
starting values: individual a = 0.4 individual b = 0.4
A       B
1804289383.532134       1804289383.306165
2651220269.054946       2651220269.827112
4332913046.416999       4332913046.791281
6047549960.973747       6047549961.979666
8005297753.938927       8005297755.381466
8429536088.122741       8429536090.737263
9149421474.458202       9149421477.268963
10799181966.514246      10799181969.109875
11395698614.754076      11395698617.892900
12585340035.563337      12585340038.882833
finished

总之,我建议

不使用 RAND() 和/或选择更合适的范围 mean
我也建议从未使用全局变量。创建一个新的 Normal 每次来这里:
```
    normal_random_generator = {mu, sigma_};
```
我不知道用那个实例重写全局变量可能有什么价值。只会降低效率。因此,这是严格等价和更有效的:
```
void move_bias_random_walk(double mu) {
    Normal nrg {mu, sigma_};
    distance_ += nrg.random();
}
```
了解你的分布的西格玛,这样你就可以预测预期的数字的方差。

固定代码1

Live On Coliru

// C/C++ standard library
#include <iostream>
#include <cstdlib>
#include <ctime>

#include <boost/random/mersenne_twister.hpp>
#include <boost/random/variate_generator.hpp>
#include <boost/random/lognormal_distribution.hpp>
#include <boost/random/random_device.hpp>

/**
 * The mt11213b generator is fast and has a reasonable cycle length
 * See http://www.boost.org/doc/libs/1_60_0/doc/html/boost_random/reference.html#boost_random.reference.generators
 */
typedef boost::mt11213b Engine;
boost::random::random_device random_device;

template<
    class Type
> struct Distribution {
    boost::variate_generator<Engine, Type> variate_generator;

    template<class... Args>
    Distribution(Args... args):
        variate_generator(Engine(random_device()), Type(args...)) {
            //variate_generator.engine().seed(random_device);
            //std::cout << "ctor test: " << variate_generator.engine()() << "\n";
        }

    double random(void) {
        double v = variate_generator();
        //std::cout << "debug: " << v << "\n";
        return v;
    }
};

typedef Distribution< boost::normal_distribution<> > Normal;

// Class Individual
class Individual {
    public:
        Individual() { } // constructor initialise value
        virtual ~Individual() = default;

        // an accessor to pass information back
        void move_bias_random_walk(double mu) {
            Normal nrg {mu, sigma_};
            distance_ += nrg.random();
        }

        // An accessor for the distance object
        double get_distance() {
            return distance_;
        }

    private:
        //containers
        double distance_ = 0.4;
        double sigma_ = 0.4;
};


int main() {
    std::cout << std::fixed;
    std::cout << "!!!Begin!!!" << std::endl;
    // Initialise two individuals in this case but there could be thousands
    Individual individual_a;
    Individual individual_b;

    std::cout << "starting values: individual a = " << individual_a.get_distance() << " individual b = " << individual_b.get_distance() << std::endl;
    // Do 10 jumps with the same mean for each individual and see where they end up each time

    std::cout << "A\tB" << std::endl;
    for (auto i = 1; i <= 10; ++i) {
        double mean = rand()%10;
        //std::cout << "mean: " << mean << "\n";
        individual_a.move_bias_random_walk(mean);
        individual_b.move_bias_random_walk(mean);
        std::cout << individual_a.get_distance() << "\t" << individual_b.get_distance() << std::endl;
    }
    std::cout << "finished" << std::endl;
}

印刷品

!!!Begin!!!
starting values: individual a = 0.400000 individual b = 0.400000
A   B
3.186589    3.754065
9.341219    8.984621
17.078740   16.054461
21.787808   21.412336
24.896861   24.272279
29.801920   29.090233
36.134987   35.568845
38.228595   37.365732
46.833353   46.410176
47.573564   47.194575
finished

简化:演示2

以下内容完全相同,但效率更高:

Live On Coliru

#include <boost/random/mersenne_twister.hpp>
#include <boost/random/normal_distribution.hpp>
#include <boost/random/random_device.hpp>
#include <iostream>

/**
 * The mt11213b generator is fast and has a reasonable cycle length
 * See http://www.boost.org/doc/libs/1_60_0/doc/html/boost_random/reference.html#boost_random.reference.generators
 */
typedef boost::mt11213b Engine;

template <typename Distribution>
class Individual {
  public:
    Individual(Engine& engine) : engine_(engine) { }

    // an accessor to pass information back
    void move_bias_random_walk(double mu) {
        Distribution dist { mu, sigma_ };
        distance_ += dist(engine_);
    }

    // An accessor for the distance object
    double get_distance() {
        return distance_;
    }

  private:
    Engine& engine_;
    //containers
    double distance_ = 0.4;
    double sigma_ = 0.4;
};

int main() {
    boost::random::random_device device;
    Engine engine(device);

    std::cout << std::fixed;
    std::cout << "!!!Begin!!!" << std::endl;

    // Initialise two individuals in this case but there could be thousands
    Individual<boost::normal_distribution<> > individual_a(engine);
    Individual<boost::normal_distribution<> > individual_b(engine);

    std::cout << "starting values: individual a = " << individual_a.get_distance() << " individual b = " << individual_b.get_distance() << std::endl;
    // Do 10 jumps with the same mean for each individual and see where they end up each time

    std::cout << "A\tB" << std::endl;
    for (auto i = 1; i <= 10; ++i) {
        double mean = rand()%10;
        individual_a.move_bias_random_walk(mean);
        individual_b.move_bias_random_walk(mean);
        std::cout << individual_a.get_distance() << "\t" << individual_b.get_distance() << std::endl;
    }
    std::cout << "finished" << std::endl;
}

音符

它共享 Engine 如你所愿
它不使用全局变量(或者,更糟的是,重新分配它们!)
否则的话,它们的行为完全相同,但代码却少得多

hassec 8 年前

我试着举一个例子来说明我认为你想要达到的目标。我希望你不介意我去掉了boost,因为我看不出在这里使用它的理由。

希望这有助于:

// C/C++ standard library
#include <cstdlib>
#include <ctime>
#include <iostream>
#include <random>

// Class Individual
class Individual
{
public:
  // an accessor to pass information back
  void move_bias_random_walk( double mu, double sigma = 0.4 )
  {
    distance_ += std::normal_distribution<double>{mu, sigma}( myEngine );
  }

  // An accessor for the distance object
  double get_distance() { return distance_; }

private:
  // containers
  double distance_ = 0.4;
  static std::mt19937 myEngine;
};

// initialize static random engine to be shared by all instances of the Inidvidual class   
auto Individual::myEngine = std::mt19937( std::time( 0 ) );

int main()
{
  std::cout << "!!!Begin!!!" << std::endl;
  // Initialise two individuals in this case but there could be thousands
  Individual individual_a{};
  Individual individual_b{};

  std::cout << "starting values: individual a = " << individual_a.get_distance()
       << " individual b = " << individual_b.get_distance() << std::endl;
  // Do 10 jumps with the same mean for each individual and see where they end up each time

  std::cout << "A\tB" << std::endl;

  // let's not use rand()
  std::default_random_engine eng{1337};
  std::uniform_real_distribution<double> uniformMean{-10,10};

  for ( auto i = 1; i <= 10; ++i ) {
    double mean = uniformMean(eng);
    individual_a.move_bias_random_walk( mean );
    individual_b.move_bias_random_walk( mean );
    std::cout << individual_a.get_distance() << " " << individual_b.get_distance() << std::endl;
  }

  std::cout << "finished" << std::endl;
  return 0;
}

它打印:

!!!Begin!!!
starting values: individual a = 0.4 individual b = 0.4
A   B
8.01456 7.68829
2.53383 1.19675
7.06496 5.74414
9.60985 9.04333
12.4008 13.4647
11.2468 13.4128
6.02199 8.24547
0.361428 2.85905
-3.28938 -1.59109
-5.99163 -4.37436
finished