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std::linear_congruential_engine

From cppreference.com
< cpp‎ | numeric‎ | random
 
 
 
 
std::linear_congruential_engine
 
Defined in header <random>
template<

    class UIntType,
    UIntType a,
    UIntType c,
    UIntType m

> class linear_congruential_engine;
(since C++11)

linear_congruential_engine is a random number engine based on Linear congruential generator (LCG).

Contents

[edit] Template parameters

UIntType - The result type generated by the generator. The effect is undefined if this is not one of unsigned short, unsigned int, unsigned long, or unsigned long long.
a - the multiplier term
c - the increment term
m - the modulus term

When m is not zero, if a >= m or c >= m is true, the program is ill-formed.

[edit] Generator properties

The size of the states of linear_congruential_engine is 1, each of them consists of a single integer.

The actual modulus m
0
is defined as follows:

  • If m is not zero, m
    0
    is m.
  • If m is zero, m
    0
    is the value of std::numeric_limits<result_type>::max() plus 1 (which means m
    0
    need not be representable as result_type).

The transition algorithm of linear_congruential_engine is TA(x
i
) = (a·x
i
+c) mod m
0
.

The generation algorithm of linear_congruential_engine is GA(x
i
) = (a·x
i
+c) mod m
0
.

The pseudo-random number generated with the current state is also the successor state.

[edit] Predefined specializations

The following specializations define the random number engine with two commonly used parameter sets:

Defined in header <random>
Type Definition
minstd_rand0 (C++11) std::linear_congruential_engine<std::uint_fast32_t,
                                16807, 0, 2147483647>

Discovered in 1969 by Lewis, Goodman and Miller, adopted as "Minimal standard" in 1988 by Park and Miller[edit]

minstd_rand (C++11)

std::linear_congruential_engine<std::uint_fast32_t,
                                48271, 0, 2147483647>
Newer "Minimum standard", recommended by Park, Miller, and Stockmeyer in 1993[edit]

[edit] Nested types

Type Definition
result_type UIntType

[edit] Data members

constexpr UIntType multiplier
[static]
a
(public static member constant)
constexpr UIntType increment
[static]
c
(public static member constant)
constexpr UIntType modulus
[static]
m
(public static member constant)
constexpr UIntType default_seed
[static]
1u
(public static member constant)

[edit] Member functions

Construction and Seeding
constructs the engine
(public member function) [edit]
(C++11)
sets the current state of the engine
(public member function) [edit]
Generation
advances the engine's state and returns the generated value
(public member function) [edit]
(C++11)
advances the engine's state by a specified amount
(public member function) [edit]
Characteristics
[static] (C++11)
gets the smallest possible value in the output range
(public static member function) [edit]
[static] (C++11)
gets the largest possible value in the output range
(public static member function) [edit]

[edit] Non-member functions

(C++11)(C++11)(removed in C++20)
compares the internal states of two pseudo-random number engines
(function) [edit]
performs stream input and output on pseudo-random number engine
(function template) [edit]

[edit] Example