Defined in header <random> | ||
---|---|---|
template< class UIntType, std::size_t w, std::size_t n, std::size_t m, std::size_t r, UIntType a, std::size_t u, UIntType d, std::size_t s, UIntType b, std::size_t t, UIntType c, std::size_t l, UIntType f > class mersenne_twister_engine; | (since C++11) |
mersenne_twister_engine
is a random number engine based on Mersenne Twister algorithm. It produces high quality unsigned integer random numbers of type UIntType
on the interval \(\scriptsize {[0,2^w)}\)[0, 2w
).
The following type aliases define the random number engine with two commonly used parameter sets:
Defined in header <random> |
|
---|---|
Type | Definition |
mt19937 (C++11) |
|
mt19937_64 (C++11) |
|
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 . |
w | - | the power of two that determines the range of values generated by the engine |
n | - | the degree of recurrence |
m | - | the middle word, an offset used in the recurrence relation defining the series x , 1 ≤ m < n |
r | - | the number of bits of the lower bit-mask, 0 ≤ r ≤ w-1 , also known as the twist value |
a | - | the conditional xor-mask, i.e. the coefficients of the rational normal form twist matrix |
u | - | 1st component of the bit-scrambling (tempering) matrix |
d | - | 2nd component of the bit-scrambling (tempering) matrix |
s | - | 3rd component of the bit-scrambling (tempering) matrix |
b | - | 4th component of the bit-scrambling (tempering) matrix |
t | - | 5th component of the bit-scrambling (tempering) matrix |
c | - | 6th component of the bit-scrambling (tempering) matrix |
l | - | 7th component of the bit-scrambling (tempering) matrix |
f | - | the initialization multiplier |
The following relations shall hold:
0 < m ≤ n
2 < w
r ≤ w
u ≤ w
s ≤ w
t ≤ w
l ≤ w
w ≤
std::numeric_limits<UIntType>::digits
a ≤ 2
w-1
b ≤ 2
w-1
c ≤ 2
w-1
d ≤ 2
w-1
f ≤ 2
w-1
Member type | Definition |
---|---|
result_type (C++11) | The integral type, UIntType , generated by the engine. Results are undefined if this is not an unsigned integral type. |
Construction and Seeding |
|
(C++11) | constructs the engine (public member function) |
(C++11) | sets the current state of the engine (public member function) |
Generation |
|
(C++11) | advances the engine's state and returns the generated value (public member function) |
(C++11) | advances the engine's state by a specified amount (public member function) |
Characteristics |
|
[static] (C++11) | gets the smallest possible value in the output range (public static member function) |
[static] (C++11) | gets the largest possible value in the output range (public static member function) |
(C++11)(C++11)(removed in C++20) | compares the internal states of two pseudo-random number engines (function) |
(C++11) | performs stream input and output on pseudo-random number engine (function template) |
constexpr size_t word_size
[static] (C++11) | the template parameter w , determines the range of values generated by the engine. (public static member constant) |
constexpr size_t state_size
[static] (C++11) | the template parameter n . The engine state is n values of UIntType (public static member constant) |
constexpr size_t shift_size
[static] (C++11) | the template parameter m (public static member constant) |
constexpr size_t mask_bits
[static] (C++11) | the template parameter r , also known as the twist value. (public static member constant) |
constexpr UIntType xor_mask
[static] (C++11) | the template parameter a , the conditional xor-mask. (public static member constant) |
constexpr size_t tempering_u
[static] (C++11) | the template parameter u , first component of the bit-scrambling (tempering) matrix (public static member constant) |
constexpr UIntType tempering_d
[static] (C++11) | the template parameter d , second component of the bit-scrambling (tempering) matrix (public static member constant) |
constexpr size_t tempering_s
[static] (C++11) | the template parameter s , third component of the bit-scrambling (tempering) matrix (public static member constant) |
constexpr UIntType tempering_b
[static] (C++11) | the template parameter b , fourth component of the bit-scrambling (tempering) matrix (public static member constant) |
constexpr size_t tempering_t
[static] (C++11) | the template parameter t , fifth component of the bit-scrambling (tempering) matrix (public static member constant) |
constexpr UIntType tempering_c
[static] (C++11) | the template parameter c , sixth component of the bit-scrambling (tempering) matrix (public static member constant) |
constexpr size_t tempering_l
[static] (C++11) | the template parameter l , seventh component of the bit-scrambling (tempering) matrix (public static member constant) |
constexpr UIntType initialization_multiplier
[static] (C++11) | the template parameter f (public static member constant) |
constexpr UIntType default_seed
[static] (C++11) | the constant value 5489u (public static member constant) |
The Nth consecutive invocation of a default-constructed engine is required to produce the following value:
N | The random engine type | The value to produce |
---|---|---|
10000 |
std::mt19937 | 4123659995 |
10000 |
std::mt19937_64 | 9981545732273789042 |
This is to guarantee that the random engine is conforming to the standard (see N1398).
#include <cassert> #include <random> int main() { std::mt19937 gen32; std::mt19937_64 gen64; gen32.discard(10'000 - 1); gen64.discard(10'000 - 1); assert(gen32() == 4'123'659'995); assert(gen64() == 9'981'545'732'273'789'042ull); }
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