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Difference between revisions of "cpp/numeric/random/discrete distribution"

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< cpp‎ | numeric‎ | random
m (list allowed types for IntType)
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{{tt|std::discrete_distribution}} produces random integers on the interval {{tt|[0, n)}}, where the probability of each individual integer {{tt|i}} is defined as {{math|w{{su|b=i}}/S}}, that is the ''weight'' of the {{tt|i}}th integer divided by the sum of all {{tt|n}} weights.  
 
{{tt|std::discrete_distribution}} produces random integers on the interval {{tt|[0, n)}}, where the probability of each individual integer {{tt|i}} is defined as {{math|w{{su|b=i}}/S}}, that is the ''weight'' of the {{tt|i}}th integer divided by the sum of all {{tt|n}} weights.  
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{{tt|std::discrete_distribution}} satisfies all requirements of {{concept|RandomNumberDistribution}}
  
 
===Template parameters===
 
===Template parameters===
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{{dsc hitem | Member type | Definition}}
 
{{dsc hitem | Member type | Definition}}
 
{{dsc | {{tt|result_type}} | {{c|IntType}}}}
 
{{dsc | {{tt|result_type}} | {{c|IntType}}}}
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{{dsc | {{tt|param_type}} | the type of the parameter set, unspecified}}
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{{cpp/numeric/random/param_type}}
 
{{dsc end}}
 
{{dsc end}}
  

Revision as of 19:14, 4 February 2015

 
C++
 
Numerics library
Common mathematical functions
Mathematical special functions (C++17)
Mathematical constants (C++20)
Basic linear algebra algorithms (C++26)
Floating-point environment (C++11)
Complex numbers
Numeric array (valarray)
Pseudo-random number generation
Factor operations
(C++17)
(C++17)
Interpolations
(C++20)
(C++20)
Saturation arithmetic
(C++26)
(C++26)
(C++26)
(C++26)
(C++26)

Generic numeric operations
Bit operations
(C++20)    
(C++20)
(C++20)
(C++20)
(C++20)
(C++20)
(C++20)
(C++20)
(C++20)
(C++20)
(C++20)
(C++20)
(C++23)
(C++20)
 
Pseudo-random number generation
 
std::discrete_distribution
 
Defined in header <random>
template< class IntType = int >
class discrete_distribution;
 (since C++11)

std::discrete_distribution produces random integers on the interval [0, n), where the probability of each individual integer i is defined as wi/S, that is the weight of the ith integer divided by the sum of all n weights.

std::discrete_distribution satisfies all requirements of Template:concept

Contents

Template parameters

IntType - The result type generated by the generator. The effect is undefined if this is not one of short, int, long, long long, unsigned short, unsigned int, unsigned long, or unsigned long long.

Member types

Member type Definition
result_type IntType
param_type (C++11) the type of the parameter set, see RandomNumberDistribution.

Member functions

(C++11)
 constructs new distribution
(public member function) [edit]
(C++11)
 resets the internal state of the distribution
(public member function) [edit]
Generation
(C++11)
 generates the next random number in the distribution
(public member function) [edit]
Characteristics
obtains the list of probabilities
(public member function) [edit]
(C++11)
 gets or sets the distribution parameter object
(public member function) [edit]
(C++11)
 returns the minimum potentially generated value
(public member function) [edit]
(C++11)
 returns the maximum potentially generated value
(public member function) [edit]

Non-member functions

(C++11)(C++11)(removed in C++20)
 compares two distribution objects
(function) [edit]
(C++11)
 performs stream input and output on pseudo-random number distribution
(function template) [edit]

Example

Run this code
#include <iostream>
#include <map>
#include <random>
 
int main()
{
    std::random_device rd;
    std::mt19937 gen(rd());
    std::discrete_distribution<> d({40, 10, 10, 40});
    std::map<int, int> m;
    for(int n=0; n<10000; ++n) {
        ++m[d(gen)];
    }
    for(auto p : m) {
        std::cout << p.first << " generated " << p.second << " times\n";
    }
}

Output: 

0 generated 4028 times
1 generated 978 times
2 generated 1012 times
3 generated 3982 times
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