CGAL 5.1.2 - Geometric Object Generators
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#include <CGAL/Random.h>
The class Random
is a random numbers generator.
It generates uniformly distributed random bool
, int
and double
. It can be used as the random number generating function object in the STL algorithm std::random_shuffle
.
Instances of Random
can be seen as input streams. Different streams are independent of each other, i.e. the sequence of numbers from one stream does not depend upon how many numbers were extracted from the other streams. At each time, an instance has a state that uniquely determines the subsequent numbers being produced.
It can be very useful, e.g. for debugging, to reproduce a sequence of random numbers. This can be done by either initialising with a fixed seed, or by using the state functions as described below.
Random
object is not deterministic when used by several threads at the same time, even if a fixed seed has been chosen.Implementation
We use the boost random library function boost::rand48
to generate the random numbers.
CGAL::get_default_random
Types | |
typedef unspecified_type | State |
The State type. | |
Creation | |
Random () | |
Default constructor. More... | |
Random (unsigned int seed) | |
Constructor initializing its internal state using seed . More... | |
Operations | |
bool | get_bool () |
returns a random bool . | |
template<int b> | |
int | get_bits () |
returns a random int value from the interval \([0,2^b)\). More... | |
int | get_int (int lower, int upper) |
returns a random int from the interval [lower,upper) . | |
double | get_double (double lower=0.0, double upper=1.0) |
returns a random double from the interval [lower,upper) . | |
Distributions | |
The following member functions are a 1-to-1 correspondence to some distributions from the boost random library. | |
template<typename IntType > | |
IntType | uniform_smallint (IntType lower=0, IntType upper=9) |
returns a random IntType from the interval [lower,upper) . More... | |
template<typename IntType > | |
IntType | uniform_int (IntType lower=0, IntType upper=9) |
returns a random IntType from the interval [lower,upper) . More... | |
template<typename RealType > | |
Realtype | uniform_real (RealType lower=0.0, RealType upper=1.0) |
returns a random RealType from the interval [lower,upper) . More... | |
template<typename RealType > | |
RealType | uniform_01 () |
returns a random RealType from the interval [0,1) . More... | |
template<typename IntType > | |
IntType | operator() (IntType upper) |
returns random uniform_int<IntType>( 0, upper-1) . | |
Seed and State Functions | |
unsigned int | get_seed () const |
returns the seed used for initialization. | |
void | save_state (State &state) const |
saves the current internal state in state . | |
void | restore_state (State const &state) |
restores the internal state from state . | |
Equality Test | |
bool | operator== (Random const &random2) const |
returns true , iff the random object and random2 have equal internal states. | |
CGAL::Random::Random | ( | ) |
Default constructor.
The seed is chosen based on the system time.
CGAL::Random::Random | ( | unsigned int | seed | ) |
Constructor initializing its internal state using seed
.
Equal values for seed
result in equal sequences of random numbers.
int CGAL::Random::get_bits | ( | ) |
returns a random int
value from the interval \([0,2^b)\).
This is supposed to be efficient.
RealType CGAL::Random::uniform_01 | ( | ) |
returns a random RealType
from the interval [0,1)
.
RealType
can be float
, double
, etc.
IntType CGAL::Random::uniform_int | ( | IntType | lower = 0 , |
IntType | upper = 9 |
||
) |
returns a random IntType
from the interval [lower,upper)
.
IntType
can be an integral type as int
, std::ptrdiff_t
, std::size_t
,etc.
get_int
this function may return upper
. Realtype CGAL::Random::uniform_real | ( | RealType | lower = 0.0 , |
RealType | upper = 1.0 |
||
) |
returns a random RealType
from the interval [lower,upper)
.
RealType
can be float
, double
, etc.
IntType CGAL::Random::uniform_smallint | ( | IntType | lower = 0 , |
IntType | upper = 9 |
||
) |
returns a random IntType
from the interval [lower,upper)
.
IntType
can be an integral type as int
, std::ptrdiff_t
, std::size_t
,etc.
get_int
this function may return upper
.