Re: [boost] Problem in random/uniform_smallint.hpp

From: Jens Maurer (Jens.Maurer_at_[hidden])
Date: 2004-01-15 14:45:08

Thanks for your effort.

Reproduced the problem and fixed it as suggested.

Jens Maurer

Mario Ruetti wrote:
> I wrote a little test program to reproduce the error. myGen is a 'generator'
> which produces uint64_t sized numbers....
> This produces a floating-point exception. See the comment at the end of this
> message how to fix this bug. 
> 
>        Mario Rütti
> 
> // snipp ----
> 
> #include <iostream>
> #include <cmath>
> 
> #include <boost/random.hpp>
> 
> 
> class myGen
> {
> public:
>   typedef uint64_t result_type;
>   result_type min() const { return 0; }
>   result_type max() const { return std::numeric_limits<  myGen::result_type
> 
>>::max(); }
> 
>   result_type operator()()
>   {
>     return std::numeric_limits<  myGen::result_type >::max()-1;
>   }
> };
> 
> 
> int main()
> {
>   // no problem
>   using boost::mt19937;
>   mt19937 rng;
>   boost::variate_generator< mt19937, boost::uniform_int<> > uni_rng( rng,
> boost::uniform_int<>(0,10) );
>   for (int i=0;i<10;i++)
>     std::cout << uni_rng() << std::endl;
> 
>  //problem (Gleitkomma-Ausnahme)
>   myGen myrng;
>   boost::variate_generator< myGen, boost::uniform_int<> > myuni_rng( myrng,
> boost::uniform_int<>(0,10) );
>   for (int i=0;i<10;i++)
>     std::cout << myuni_rng() << std::endl;
> }
> 
> // snapp ----
> 
> 
> // Change in 'uniform_smallint.hpp' in
> 
> // template<class IntType = int>
> // class uniform_smallint
> // {
> // .....
> 
> //   template<class Engine>
> //   result_type operator()(Engine& eng)
> //   {
> //     typedef typename Engine::result_type base_result;
> //     base_result _range = static_cast<base_result>(_max-_min)+1;
> // //    int _factor = 1;        <-- original code
> //     base_result _factor = 1;  <-- replacement
> //     ^^^^^^^^^^^^^^^^^^^^^^^^
> //       int is to small, use base_result as type for _factor
>