NAME

std::mersenne_twister_engine::mersenne_twister_engine - std::mersenne_twister_engine::mersenne_twister_engine

Synopsis

mersenne_twister_engine() : (1) (since C++11)
mersenne_twister_engine(default_seed) {}
explicit mersenne_twister_engine( result_type value ); (2) (since C++11)
template< class Sseq > (3) (since C++11)
explicit mersenne_twister_engine( Sseq& s );
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 sets the current state of the engine
(C++11) (public member function)