...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::lagged_fibonacci_01_engine
// In header: <boost/random/lagged_fibonacci.hpp> template<typename RealType, int w, unsigned int p, unsigned int q> class lagged_fibonacci_01_engine { public: // types typedef RealType result_type; // construct/copy/destruct lagged_fibonacci_01_engine(); explicit lagged_fibonacci_01_engine(uint32_t); template<typename SeedSeq> explicit lagged_fibonacci_01_engine(SeedSeq &); template<typename It> lagged_fibonacci_01_engine(It &, It); // public member functions void seed(); void seed(boost::uint32_t); template<typename SeedSeq> void seed(SeedSeq &); template<typename It> void seed(It &, It); result_type operator()(); template<typename Iter> void generate(Iter, Iter); void discard(boost::uintmax_t); // public static functions static result_type min(); static result_type max(); // friend functions template<typename CharT, typename Traits> friend std::basic_ostream< CharT, Traits > & operator<<(std::basic_ostream< CharT, Traits > &, const lagged_fibonacci_01_engine &); template<typename CharT, typename Traits> friend std::basic_istream< CharT, Traits > & operator>>(std::basic_istream< CharT, Traits > &, const lagged_fibonacci_01_engine &); friend bool operator==(const lagged_fibonacci_01_engine &, const lagged_fibonacci_01_engine &); friend bool operator!=(const lagged_fibonacci_01_engine &, const lagged_fibonacci_01_engine &); // public data members static const bool has_fixed_range; static const int word_size; static const unsigned int long_lag; static const unsigned int short_lag; static const boost::uint32_t default_seed; };
Instantiations of class template lagged_fibonacci_01
model a pseudo-random number generator . It uses a lagged Fibonacci algorithm with two lags p
and q
, evaluated in floating-point arithmetic: x(i) = x(i-p) + x(i-q) (mod 1) with p > q. See
"Uniform random number generators for supercomputers", Richard Brent, Proc. of Fifth Australian Supercomputer Conference, Melbourne, Dec. 1992, pp. 704-706.
Note | |
---|---|
The quality of the generator crucially depends on the choice of the parameters. User code should employ one of the sensibly parameterized generators such as lagged_fibonacci607 instead. |
The generator requires considerable amounts of memory for the storage of its state array. For example, lagged_fibonacci607 requires about 4856 bytes and lagged_fibonacci44497 requires about 350 KBytes.
lagged_fibonacci_01_engine
public
construct/copy/destructlagged_fibonacci_01_engine();
Constructs a lagged_fibonacci_01
generator and calls seed()
.
explicit lagged_fibonacci_01_engine(uint32_t value);
Constructs a lagged_fibonacci_01
generator and calls seed(value)
.
template<typename SeedSeq> explicit lagged_fibonacci_01_engine(SeedSeq & seq);
Constructs a lagged_fibonacci_01
generator and calls seed(gen)
.
template<typename It> lagged_fibonacci_01_engine(It & first, It last);
lagged_fibonacci_01_engine
public member functionsvoid seed();
Calls seed(default_seed).
void seed(boost::uint32_t value);
Constructs a minstd_rand0
generator with the constructor parameter value and calls seed with it. Distinct seeds in the range [1, 2147483647) will produce generators with different states. Other seeds will be equivalent to some seed within this range. See linear_congruential_engine
for details.
template<typename SeedSeq> void seed(SeedSeq & seq);
Seeds this
using values produced by lagged_fibonacci_01_engine
seq.generate
.
template<typename It> void seed(It & first, It last);
Seeds this
using values from the iterator range [first, last). If there are not enough elements in the range, throws lagged_fibonacci_01_engine
std::invalid_argument
.
result_type operator()();
Returns the next value of the generator.
template<typename Iter> void generate(Iter first, Iter last);
Fills a range with random values
void discard(boost::uintmax_t z);
Advances the state of the generator by z
.
lagged_fibonacci_01_engine
friend functionstemplate<typename CharT, typename Traits> friend std::basic_ostream< CharT, Traits > & operator<<(std::basic_ostream< CharT, Traits > & os, const lagged_fibonacci_01_engine & f);
Writes the textual representation of the generator to a std::ostream
.
template<typename CharT, typename Traits> friend std::basic_istream< CharT, Traits > & operator>>(std::basic_istream< CharT, Traits > & is, const lagged_fibonacci_01_engine & f);
Reads the textual representation of the generator from a std::istream
.
friend bool operator==(const lagged_fibonacci_01_engine & x_, const lagged_fibonacci_01_engine & y_);
Returns true if the two generators will produce identical sequences of outputs.
friend bool operator!=(const lagged_fibonacci_01_engine & lhs, const lagged_fibonacci_01_engine & rhs);
Returns true if the two generators will produce different sequences of outputs.