Varianti

    std::piecewise_linear_distribution

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    <metanoindex/>

     
    C++
     
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    Bernoulli distributions
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    bernoulli_distribution(C++11)
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    std::piecewise_linear_distribution
    Membri funzioni
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    Member functions
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    piecewise_linear_distribution::piecewise_linear_distribution
    piecewise_linear_distribution::reset
    Generazione
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    Generation
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    piecewise_linear_distribution::operator()
    Caratteristiche
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    Characteristics
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    piecewise_linear_distribution::param
    piecewise_linear_distribution::min
    piecewise_linear_distribution::max
    Non membri funzioni
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    Non-member functions
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    operator==
    operator!=
    operator<<
    operator>>
     
    <tbody> </tbody>
    Elemento definito nell'header <random>
    template< class RealType = double > class piecewise_linear_distribution;
    		 (dal C++11)

    std::piecewise_linear_distribution produces random floating-point numbers, which are distributed according to a linear probability density function within each of the several subintervals [b
    i    , b
    i+1    )    . The distribution is such that the probability density at each interval boundary is exactly the predefined value p
    i    .

    The probability density for any b
    i    ≤x<b
    i+1     is

    p
    i
    b
    i+1    -x
    b
    i+1    -b
    i
    + p
    i+1
    x-b
    i
    b
    i+1    -b
    i

    , where probability densities at interval boundaries p
    k     are calculated as w
    k    /S     where S is the sum of all

    None
    1
    2
    (w
    k    +w
    k+1    )(b
    k+1    −b
    k    )

    .

    The set of interval boundaries b
    i     and the set of weights at boundaries w
    i     are the parameters of this distribution.

    Membri tipi

    Membro tipo
    Original:
    Member type
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    		 Definition
    result_type RealType
    param_type
    il tipo di set di parametri, non specificato
    Original:
    the type of the parameter set, unspecified
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    Membri funzioni
    costruisce nuova distribuzione
    Original:
    constructs new distribution
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    (metodo pubblico) [modifica]
    ripristina lo stato interno della distribuzione
    Original:
    resets the internal state of the distribution
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    (metodo pubblico) [modifica]
    Generazione
    Original:
    Generation
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    genera il successivo numero casuale nella distribuzione
    Original:
    generates the next random number in the distribution
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    (metodo pubblico) [modifica]
    Caratteristiche
    Original:
    Characteristics
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    ottiene l'elenco dei confini intervallo
    Original:
    obtains the list of interval boundaries
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    (metodo pubblico) [modifica]
    ottiene l'elenco delle densità di probabilità ai confini intervallo
    Original:
    obtains the list of probability densities at interval boundaries
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    (metodo pubblico) [modifica]
    ottiene o imposta l'oggetto parametro di distribuzione
    Original:
    gets or sets the distribution parameter object
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    (metodo pubblico) [modifica]
    restituisce il valore minimo potenzialmente generato
    Original:
    returns the minimum potentially generated value
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    (metodo pubblico) [modifica]
    restituisce il valore massimo potenzialmente generato
    Original:
    returns the maximum potentially generated value
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    (metodo pubblico) [modifica]

    Non membri funzioni
    confronta due oggetti di distribuzione
    Original:
    compares two distribution objects
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    (funzione) [modifica]
    esegue flusso di ingresso e di uscita sul pseudo-casuale distribuzione numerica
    Original:
    performs stream input and output on pseudo-random number distribution
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    (funzione) [modifica]

    Esempio

    #include <iostream>
#include <iomanip>
#include <string>
#include <map>
#include <random>

int main()
{
    std::random_device rd;
    std::mt19937 gen(rd());
    // increase the probability from 0 to 5
    // remain flat from 5 to 10
    // decrease from 10 to 15 at the same rate
    std::vector<double> i{0, 5, 10, 15};
    std::vector<double> w{0, 1,   1, 0};
    std::piecewise_linear_distribution<> d(i.begin(), i.end(), w.begin());

    std::map<int, int> hist;
    for(int n=0; n<10000; ++n) {
        ++hist[d(gen)];
    }
    for(auto p : hist) {
        std::cout << std::setw(2) << p.first << ' ' << std::string(p.second/100,
    }
}

    Output: 

    0 *
 1 ***
 2 ****
 3 ******
 4 *********
 5 *********
 6 *********
 7 **********
 8 *********
 9 **********
10 *********
11 *******
12 ****
13 ***
14 *