std::linear_congruential_engine

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Numerics library

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(C++17)

(C++17)

(C++20)

(C++20)

Generic numeric operations

iota (C++11)
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reduce (C++17)
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C-style checked integer arithmetic

ckd_add (C++26)
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ckd_mul (C++26)

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Pseudo-random number generation

Uniform random bit generators

uniform_random_bit_generator

(C++20)

Random number engines

linear_congruential_engine

(C++11)

mersenne_twister_engine

(C++11)

subtract_with_carry_engine

(C++11)

philox_engine

(C++26)

Random number engine adaptors

discard_block_engine

(C++11)

independent_bits_engine

(C++11)

shuffle_order_engine

(C++11)

Predefined random number generators

Non-deterministic random numbers

(C++11)

(C++11)

(C++11)

Random number algorithms

ranges::generate_random

(C++26)

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uniform_int_distribution (C++11)
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generate_canonical (C++11)
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negative_binomial_distribution (C++11)
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poisson_distribution (C++11)
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extreme_value_distribution (C++11)
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normal_distribution (C++11)
lognormal_distribution (C++11)
chi_squared_distribution (C++11)
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Sampling distributions
discrete_distribution (C++11)
piecewise_constant_distribution (C++11)
piecewise_linear_distribution (C++11)

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std::linear_congruential_engine

Member functions
linear_congruential_engine::linear_congruential_engine
linear_congruential_engine::seed
Generation
linear_congruential_engine::operator()
linear_congruential_engine::discard
Characteristics
linear_congruential_engine::min
linear_congruential_engine::max
Non-member functions
operator==operator!= (C++11)(C++11)(until C++20)
operator<<operator>> (C++11)(C++11)

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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 onLinear congruential generator (LCG).

[edit]Template parameters

UIntType	-	The result type generated by the generator. The effect is undefined if this is not one ofunsignedshort,unsignedint,unsignedlong, orunsignedlonglong.
a	-	the multiplier term
c	-	the increment term
m	-	the modulus term

Whenm is not zero, ifa>= m orc>= m istrue, the program is ill-formed.

[edit]Generator properties

Thesize of the states oflinear_congruential_engine is1, each of them consists of a single integer.

The actual modulus\(\scriptsize m_0\)m0 is defined as follows:

Ifm is not zero,\(\scriptsize m_0\)m0 ism.
Ifm is zero,\(\scriptsize m_0\)m0 is the value ofstd::numeric_limits<result_type>::max() plus1 (which means\(\scriptsize m_0\)m0 need not be representable asresult_type).

Thetransition algorithm oflinear_congruential_engine is\(\scriptsize TA(x_i) = (a \cdot x_i + c)\mod m_0\)TA(xi) = (a·xi+c) mod m0.

Thegeneration algorithm oflinear_congruential_engine is\(\scriptsize GA(x_i) = (a \cdot x_i + c)\mod m_0\)GA(xi) = (a·xi+c) mod m0.

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
(constructor)	constructs the engine (public member function)[edit]
seed	sets the current state of the engine (public member function)[edit]
Generation
operator()	advances the engine's state and returns the generated value (public member function)[edit]
discard	advances the engine's state by a specified amount (public member function)[edit]
Characteristics
min [static]	gets the smallest possible value in the output range (public static member function)[edit]
max [static]	gets the largest possible value in the output range (public static member function)[edit]

[edit]Non-member functions

operator==operator!= (C++11)(C++11)(removed in C++20)	compares the internal states of two pseudo-random number engines (function)[edit]

operator<<operator>> (C++11)	performs stream input and output on pseudo-random number engine (function template)[edit]