Re: [boost] [Random]Random value from range

Subject: Re: [boost] [Random]Random value from range
From: Steven Watanabe (watanabesj_at_[hidden])
Date: 2010-01-03 13:59:56

AMDG

Mariusz Kwiczala wrote:
> After experiments I wrote below function.
> Could you verify if function is written correctly for random value from
> range [min,max) and
> uniform distribution? 
>
> double RandomGenerator(const double min, const double max)
> {
> assert(min<max);
> static boost::lagged_fibonacci44497 gen(static_cast<unsigned 
> int>(std::time(0)));
> static boost::uniform_real<> range(min, max);
> static boost::variate_generator<boost::lagged_fibonacci44497&, 
> boost::uniform_real<> > generator(gen, range);
> const double value = generator();
> return value;
> }
>
> I have few question related to random library:
> 1.       Is it possibility to write function which will generate numbers 
> from range [min, max] or (min, max)
>   

(min, max) can be handled by rejection from [min, max).
[min, max] is a bit trickier.  Either way, you'll have to implement
it yourself.

> 2.       Why generator (boost::lagged_fibonacci44497)is not properly 
> initialized in some default constructor. Without static_cast<unsigned 
> int>(std::time(0)) code generated the same values after every application 
> run.
>   

This is a feature.

> 3.       Why when I missed reference "&" in line 
> boost::variate_generator<boost::lagged_fibonacci44497&, application crashes.
>   

Probably stack overflow.  boost::lagged_fibonacci44497 is
rather large.

> Is it bug?
>   

In Christ,
Steven Watanabe