std::mersenne_twister_engine<UIntType,w,n,m,r,a,u,d,s,b,t,c,l,f>::mersenne_twister_engine

 

C++

Compiler support

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Named requirements

Feature test macros (C++20)

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Technical specifications

Symbols index

External libraries

 

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endian (C++20)

 

Pseudo-random number generation

Uniform random bit generators

uniform_random_bit_generator (C++20)

Engines and engine adaptors

linear_congruential_engine (C++11)

mersenne_twister_engine (C++11)

subtract_with_carry_engine (C++11)

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independent_bits_engine (C++11)

shuffle_order_engine (C++11)

Non-deterministic generator

random_device (C++11)

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uniform_int_distribution (C++11)

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poisson_distribution (C++11)

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normal_distribution (C++11)

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discrete_distribution (C++11)

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piecewise_linear_distribution (C++11)

Seed Sequences

seed_seq (C++11)

C library

rand

srand

RAND_MAX

 

std::mersenne_twister_engine

Member functions

mersenne_twister_engine::mersenne_twister_engine (C++11)

mersenne_twister_engine::seed (C++11)

Generation

mersenne_twister_engine::operator() (C++11)

mersenne_twister_engine::discard (C++11)

Characteristics

mersenne_twister_engine::min (C++11)

mersenne_twister_engine::max (C++11)

Non-member functions

operator==operator!= (C++11)(C++11)(until C++20)

operator<<operator>> (C++11)(C++11)

 

mersenne_twister_engine() : mersenne_twister_engine(default_seed) {}	(1)	(since C++11)
explicit mersenne_twister_engine( result_type value );	(2)	(since C++11)
template< class Sseq > explicit mersenne_twister_engine( Sseq& s );	(3)	(since C++11)
mersenne_twister_engine( const mersenne_twister_engine& );	(4)	(since C++11) (implicitly declared)

Constructs the pseudo-random number engine.

1) Default constructor. Seeds the engine with default_seed.

2) Constructs the engine and initializes the state (n values X
i of type result_type) as follows: value mod 2w
is used to initialize X
0 and the rest are initialized iteratively, for i=1-n,...,-1, each X
i is initialized to [f·(X
i-1xor(X
i-1rshift(w-2)))+i mod n] mod 2w

3) Constructs the engine and initializes the state by calling s.generate(a, a+n*k) where a is an array of length n*k and k is ceil(w/32) and then, iteratively for i=-n,...,-1, setting each element of the engine state X
i to (Σk-1
j=0a
k(i+n)+j}·232j
) mod 2w
, and finally if the most significant w-r bits of X
0 are zero, and if all other X
i are zero, replacing X
0 with 2w-1
.

Note: initialization requirements are based on the 2002 version of Mersenne Twister, mt19937ar.c

The overload (3) only participates in overload resolution if Sseq qualifies as a SeedSequence. In particular, it is excluded from the set of candidate functions if Sseq is convertible to result_type.

Parameters

value	-	seed value to use in the initialization of the internal state
s	-	seed sequence to use in the initialization of the internal state

Complexity

Linear in n (the state size).

Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

DR	Applied to	Behavior as published	Correct behavior
P0935R0	C++11	default constructor was explicit	made implicit

See also

seed (C++11)

sets the current state of the engine (public member function)