...one of the most highly
regarded and expertly designed C++ library projects in the
world.
— Herb Sutter and Andrei
Alexandrescu, C++
Coding Standards
boost::random::additive_combine
// In header: <boost/random/additive_combine.hpp> template<typename MLCG1, typename MLCG2, typename MLCG1::result_type val> class additive_combine { public: // types typedef MLCG1 first_base; typedef MLCG2 second_base; typedef MLCG1::result_type result_type; // construct/copy/destruct additive_combine(); additive_combine(result_type); additive_combine(typename MLCG1::result_type, typename MLCG2::result_type); template<typename It> additive_combine(It &, It); // public member functions result_type min() const; result_type max() const; void seed(); void seed(result_type); void seed(typename MLCG1::result_type, typename MLCG2::result_type); template<typename It> void seed(It &, It); result_type operator()(); // public static functions static bool validation(result_type); // friend functions template<typename CharT, typename Traits> friend std::basic_ostream< CharT, Traits > & operator<<(std::basic_ostream< CharT, Traits > &, const additive_combine &); template<typename CharT, typename Traits> friend std::basic_istream< CharT, Traits > & operator>>(std::basic_istream< CharT, Traits > &, additive_combine &); friend bool operator==(const additive_combine &, const additive_combine &); friend bool operator!=(const additive_combine &, const additive_combine &); static const bool has_fixed_range; static const result_type min_value; static const result_type max_value; };
An instantiation of class template additive_combine model a pseudo-random number generator . It combines two multiplicative linear_congruential number generators, i.e. those with c
= 0. It is described in
"Efficient and Portable Combined Random Number Generators", Pierre L'Ecuyer, Communications of the ACM, Vol. 31, No. 6, June 1988, pp. 742-749, 774
The template parameters MLCG1 and MLCG2 shall denote two different linear_congruential number generators, each with c = 0. Each invocation returns a random number X(n) := (MLCG1(n) - MLCG2(n)) mod (m1 - 1), where m1 denotes the modulus of MLCG1.
The template parameter val
is the validation value checked by validation.
additive_combine
public
construct/copy/destructadditive_combine();
Constructs an additive_combine
generator using the default constructors of the two base generators.
additive_combine(result_type aseed);
Constructs an additive_combine
generator, using aseed as the constructor argument for both base generators.
additive_combine(typename MLCG1::result_type seed1, typename MLCG2::result_type seed2);
Constructs an additive_combine
generator, using seed1
and seed2
as the constructor argument to the first and second base generators, respectively.
template<typename It> additive_combine(It & first, It last);
Contructs an additive_combine
generator with values from the range defined by the input iterators first and last. first will be modified to point to the element after the last one used.
Throws: std::invalid_argument
if the input range is too small.
Exception Safety: Basic
additive_combine
public member functionsresult_type min() const;
Returns: The smallest value that the generator can produce
result_type max() const;
Returns: The largest value that the generator can produce
void seed();
Seeds an additive_combine
generator using the default seeds of the two base generators.
void seed(result_type aseed);
Seeds an additive_combine
generator, using aseed
as the seed for both base generators.
void seed(typename MLCG1::result_type seed1, typename MLCG2::result_type seed2);
Seeds an additive_combine
generator, using seed1
and seed2
as the seeds to the first and second base generators, respectively.
template<typename It> void seed(It & first, It last);
Seeds an additive_combine
generator with values from the range defined by the input iterators first and last. first will be modified to point to the element after the last one used.
Throws: std::invalid_argument
if the input range is too small.
Exception Safety: Basic
result_type operator()();
Returns: the next value of the generator
additive_combine
friend functionstemplate<typename CharT, typename Traits> friend std::basic_ostream< CharT, Traits > & operator<<(std::basic_ostream< CharT, Traits > & os, const additive_combine & r);
Writes the state of an additive_combine
generator to a std::ostream
. The textual representation of an additive_combine
generator is the textual representation of the first base generator followed by the textual representation of the second base generator.
template<typename CharT, typename Traits> friend std::basic_istream< CharT, Traits > & operator>>(std::basic_istream< CharT, Traits > & is, additive_combine & r);
Reads the state of an additive_combine
generator from a std::istream
.
friend bool operator==(const additive_combine & x, const additive_combine & y);
Returns: true iff the two additive_combine
generators will produce the same sequence of values.
friend bool operator!=(const additive_combine & x, const additive_combine & y);
Returns: true iff the two additive_combine
generators will produce different sequences of values.