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linear_congruential_engine Class

  • Artikkel

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

See also

<random>