linear_congruential_engine Class
Generates a random sequence by the linear congruential algorithm.
Syntax
class linear_congruential_engine{
public: // types
typedef UIntType result_type;
// engine characteristics
static constexpr result_type multiplier = a;
static constexpr result_type increment = c;
static constexpr result_type modulus = m;
static constexpr result_type min() { return c == 0u 1u: 0u; }
static constexpr result_type max() { return m - 1u; }
static constexpr result_type default_seed = 1u;
// constructors and seeding functions
explicit linear_congruential_engine(result_type s = default_seed);
template <class Sseq>
explicit linear_congruential_engine(Sseq& q);
void seed(result_type s = default_seed);
template <class Sseq>
void seed(Sseq& q);
// generating functions
result_type operator()();
void discard(unsigned long long z);
};
Parameters
UIntType
The unsigned integer result type. For possible types, see <random>.
A
Multiplier. Precondition: See Remarks section.
C
Increment. Precondition: See Remarks section.
M
Modulus. Precondition: See remarks.
Members
linear_congruential_engine::linear_congruential_engine
linear_congruential_engine::discard
linear_congruential_engine::max
linear_congruential_engine::min
linear_congruential_engine::operator()
linear_congruential_engine::seed
default_seed
is a member constant, defined as 1u
, used as the default parameter value for linear_congruential_engine::seed
and the single value constructor.
For more information about engine members, see <random>.
Remarks
The linear_congruential_engine
class template is the simplest generator engine, but not the fastest or highest quality. An improvement over this engine is the substract_with_carry_engine. Neither of these engines is as fast or with as high quality results as the mersenne_twister_engine.
This engine produces values of a user-specified unsigned integral type using the recurrence relation ( period) x(i) = (A * x(i-1) + C) mod M
.
If M is zero, the value used for this modulus operation is numeric_limits<result_type>::max() + 1
. The engine's state is the last value returned, or the seed value if no call has been made to operator()
.
If M is not zero, the values of the template arguments A and C must be less than M.
Although you can construct a generator from this engine directly, you can also use one of these predefined typedefs.
minstd_rand0
: 1988 minimal standard engine (Lewis, Goodman, and Miller, 1969).
typedef linear_congruential_engine<unsigned int, 16807, 0, 2147483647> minstd_rand0;
minstd_rand
: Updated minimal standard engine minstd_rand0
(Park, Miller, and Stockmeyer, 1993).
typedef linear_congruential_engine<unsigned int, 48271, 0, 2147483647> minstd_rand;
For detailed information about the linear congruential engine algorithm, see the Wikipedia article Linear congruential generator.
Requirements
Header: <random>
Namespace: std