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boost::random::inversive_congruential_engine
// In header: <boost/random/inversive_congruential.hpp> template<typename IntType, a, b, p> class inversive_congruential_engine { public: // types typedef IntType ; // construct/copy/destruct (); (IntType); template<typename SeedSeq> (SeedSeq &); template<typename It> (It &, It); // public static functions constexpr (); constexpr (); // public member functions void (); void (IntType); template<typename SeedSeq> void (SeedSeq &); template<typename It> void (It &, It); IntType (); template<typename Iter> void (Iter, Iter); void (boost::uintmax_t); // friend functions template<typename CharT, typename Traits> CharT, Traits > & (CharT, Traits > &, const inversive_congruential_engine &); template<typename CharT, typename Traits> CharT, Traits > & (CharT, Traits > &, const inversive_congruential_engine &); bool (const inversive_congruential_engine &, const inversive_congruential_engine &); bool (const inversive_congruential_engine &, const inversive_congruential_engine &); // public data members static const bool has_fixed_range; static const multiplier; static const increment; static const modulus; static const IntType default_seed; };
Instantiations of class template inversive_congruential_engine
model a pseudo-random number generator . It uses the inversive congruential algorithm (ICG) described in
"Inversive pseudorandom number generators: concepts, results and links", Peter Hellekalek, In: "Proceedings of the 1995 Winter Simulation Conference", C. Alexopoulos, K. Kang, W.R. Lilegdon, and D. Goldsman (editors), 1995, pp. 255-262. ftp://random.mat.sbg.ac.at/pub/data/wsc95.ps
The output sequence is defined by x(n+1) = (a*inv(x(n)) - b) (mod p), where x(0), a, b, and the prime number p are parameters of the generator. The expression inv(k) denotes the multiplicative inverse of k in the field of integer numbers modulo p, with inv(0) := 0.
The template parameter IntType shall denote a signed integral type large enough to hold p; a, b, and p are the parameters of the generators. The template parameter val is the validation value checked by validation.
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Note |
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The implementation currently uses the Euclidian Algorithm to compute the multiplicative inverse. Therefore, the inversive generators are about 10-20 times slower than the others (see section"performance"). However, the paper talks of only 3x slowdown, so the Euclidian Algorithm is probably not optimal for calculating the multiplicative inverse. |
inversive_congruential_engine
public
construct/copy/destruct();
Constructs an
, seeding it with the default seed. inversive_congruential_engine
(IntType x0);
Constructs an
, seeding it with inversive_congruential_engine
x0
.
template<typename SeedSeq> (SeedSeq & seq);
Constructs an
, seeding it with values produced by a call to inversive_congruential_engine
seq.generate()
.
template<typename It> (It & first, It last);
Constructs an
, seeds it with values taken from the itrator range [first, last), and adjusts first to point to the element after the last one used. If there are not enough elements, throws inversive_congruential_engine
std::invalid_argument
.
first and last must be input iterators.
inversive_congruential_engine
public member functionsvoid ();
Calls seed(default_seed)
void (IntType x0);
If c mod m is zero and x0 mod m is zero, changes the current value of the generator to 1. Otherwise, changes it to x0 mod m. If c is zero, distinct seeds in the range [1,m) will leave the generator in distinct states. If c is not zero, the range is [0,m).
template<typename SeedSeq> void (SeedSeq & seq);
Seeds an
using values from a SeedSeq. inversive_congruential_engine
template<typename It> void (It & first, It last);
seeds an
with values taken from the itrator range [first, last) and adjusts inversive_congruential_engine
first
to point to the element after the last one used. If there are not enough elements, throws std::invalid_argument
.
first
and last
must be input iterators.
IntType ();
Returns the next output of the generator.
template<typename Iter> void (Iter first, Iter last);
Fills a range with random values
void (boost::uintmax_t z);
Advances the state of the generator by z
.
inversive_congruential_engine
friend functionstemplate<typename CharT, typename Traits> CharT, Traits > & (CharT, Traits > & os, const inversive_congruential_engine & x);
Writes the textual representation of the generator to a std::ostream
.
template<typename CharT, typename Traits> CharT, Traits > & (CharT, Traits > & is, const inversive_congruential_engine & x);
Reads the textual representation of the generator from a std::istream
.
bool (const inversive_congruential_engine & x, const inversive_congruential_engine & y);
Returns true if the two generators will produce identical sequences of outputs.
bool (const inversive_congruential_engine & lhs, const inversive_congruential_engine & rhs);
Returns true if the two generators will produce different sequences of outputs.