Catalog
2.2 member functions of engine
3.2 member functions of distribution
Refer to the second edition of C + + standard library
1. Random number
1) Engine: the source of randomness, used to generate random numbers;
2) Distribution: random value, random range of random number;
3) Random number: use the engine to randomly select a value within the distribution range.
2, engine
2.1 type of engine
Foundation engine linear_congruential_engine mersenne_twister_engine subtract_with_carry_engine //Engine adapter discard_block_engine independent_bits_engine shuffle_order_engine //Engine adapter with parameters minstd_rand minstd_rand0 mt19937 mt19937_64 ranlux24_base ranlux48_base ranlux24 ranlux48 knuth_b default_random_engine //The only engine with the same sequence generated on different platforms
2.2 member functions of engine
engine e; default construction engine e(s); build an engine in the state of S engine e(e2); replication construction e.seed(); set engine to initial state e.seed(s); set the engine to the state of S e(); returns a random value e.discard(n); advance N states e1 == e2; whether the states are equal E1! = E2; status is not equal OS < E; write the state of e to output stream os Is > > e; read a state from input stream is and put it into e
2.3 test
#include <iostream>
#include <random>
#include <algorithm>
#include <vector>
#include <sstream>
using namespace std;
int main()
{
//Engine: the source of randomness.
default_random_engine dre;
//Integer. The resulting random number is distributed in [10,20]
//Parameter 1 can be 0 by default, and the maximum value of parameter 2 is the maximum value of numeric_limits < type >:: max() type
uniform_int_distribution<int> di(10, 20);
for ( int i = 0; i < 20; ++i)
{
cout << di(dre) << ends;
}
cout << endl;
//Floating point type. The values are distributed in the [10.0,20.0) range
uniform_real_distribution<double> dr(10, 20);
for ( int i = 0; i < 8; ++i)
{
cout << dr(dre) << ends;
}
cout << endl;
//Test save stream status
stringstream state;
state << dre;
for ( int i = 0; i < 3; ++i)
{
cout << dr(dre) << ends;
}
cout << endl;
state >> dre;
for (int i = 0; i < 3; ++i)
{
cout << dr(dre) << ends;
}
cout << endl;
vector<int> myVec = { 1, 2, 3, 4, 5, 6, 7, 8 };
//Shuffle the cards. Rearrange elements with default? Random? Engine
shuffle(myVec.begin(), myVec.end(), dre);
for ( auto x : myVec)
{
cout << x << ends;
}
cout << endl;
//Engines created at the same time, randomly
//shuffle(myVec.begin(), myVec.end(), default_random_engine());
system("pause");
}
//16 13 20 19 14 17 10 16 15 14 12 13 13 18 10 15 12 13 12 17
//17.2584 19.8111 11.0986 17.9811 12.9703 10.0478 11.1246 16.3976
//18.7843 15.0366 17.9793
//18.7843 15.0366 17.9793
//7 5 1 8 4 2 3 6
//Please press any key to continue3, distribution
3.1 types of distribution
uniform distribution
Uniform? Int? Distribution integer
Uniform? Real? Distribution floating point
Bernoulli distribution
Bernoulli? Distribution Boolean
Binary distribution integer
Geometric distribution integer
Negative binary distribution integer
Poisson distribution
Poisson distribution integer
Exponential distribution floating point
Gamma distribution floating point
Weibull distribution floating point
Extreme? Value? Distribution floating point
Normal distribution
Normal distribution floating point
Lognormal? Distribution floating point
Chi square distribution floating point
Cauchy? Distribution floating point
Fisher? Distribution floating point
Student? Distribution floating point
Sampling distribution
Discrete? Distribution integer
Pipewise & constant & distribution floating point
Pipewise linear distribution floating point
3.2 member functions of distribution
Distr:: result'u type distr d; default construction distr d(args); with args as the parameter, create the distribution d(e); returns a random value. Values in d-region of random distribution of propulsion engine d.min(); returns the minimum value d.max(); returns the maximum value d1 == d2; judge whether the states are equal D1! = D2; judge whether the status is unequal OS < d; writes the state of d to the output stream Is > > d; read status from input stream to d distr::param_type; parameter type distr d(pt); create a distribution and parameterize it with param_type pt d.param(); returns the current parameterized type d(e,pt); returns the next value according to the engine and parameter type, and advances the engine d.param; returns the value of param
3.3 test
#include <iostream>
#include <random>
#include <algorithm>
#include <string>
using namespace std;
template <typename Distr, typename Eng>
void distr(Distr d, Eng e, const string & name)
{
cout << name << ":" << endl;
cout << "min() = " << d.min() << endl;
cout << "max() = " << d.max() << endl;
cout << "values : " << d(e) << ends
<< d(e) << ends
<< d(e) << ends
<< d(e) << endl;
}
int main()
{
knuth_b e;
uniform_real_distribution<> ud(0, 10);
distr(ud, e, "uniform_real_distribution");
normal_distribution<> nd;
distr(nd, e, "normal_distribution");
exponential_distribution<> ed;
distr(ed, e, "normal_distribution");
gamma_distribution<> gd;
distr(gd, e, "normal_distribution");
system("pause");
}
//uniform_real_distribution:
//min() = 0
//max() = 10
//values : 8.30965 1.30427 9.47764 3.83416
//normal_distribution :
//min() = 4.94066e-324
//max() = 1.79769e+308
//values : 0.117963 - 0.131724 0.538967 - 0.140331
//normal_distribution :
//min() = 0
//max() = 1.79769e+308
//values : 1.77765 0.139753 2.95199 0.48356
//normal_distribution :
//min() = 4.94066e-324
//max() = 1.79769e+308
//values : 1.77765 0.139753 2.95199 0.48356
//Please press any key to continue
