RE: [boost] Unit test could usefully output more significantdigits to log files?

From: Paul A Bristow (pbristow_at_[hidden])
Date: 2004-07-26 15:34:37

| -----Original Message-----
| From: boost-bounces_at_[hidden] 
| [mailto:boost-bounces_at_[hidden]] On Behalf Of Victor A. 
| Wagner Jr.
| Sent: 26 July 2004 19:53
| To: boost_at_[hidden]
| Subject: Re: [boost] Unit test could usefully output more 
| significantdigits to log files?
| 
| >In test_tools.hpp, I have added an increase to the ostream precision
| >(default only 6 digits) int print_log_value thus
| >
| >   template<typename T>
| >   struct print_log_value {
| >   void    operator()( std::ostream& ostr, T const& t )
| >   {
| >     if(std::numeric_limits<T>::is_specialized &&
| >std::numeric_limits<T>::radix == 2)
| >     { // Show all possibly significant digits (for example, 
| 17 for 64-bit
| >double).
| >       ostr.precision(2 + std::numeric_limits<T>::digits * 301/1000);
| 
| is there some reason you didn't:
|       ostr.precision(2 + std::numeric_limits<T>::digits10);
| instead of estimating log(2)?  (301/1000)
| 

Yes - it was to get all possibly significant digits, rather than all
guaranteed.
You need to estimate log2 because the compiler won't do the necessary fp
calculations.

Sometimes this is more helpful - and since this a diagnostic, it seemed a
little better.

However digits10 would also be much better than default 6 precision.

Paul

Paul A Bristow
Prizet Farmhouse, Kendal, Cumbria UK LA8 8AB
[phone]  [phone]
mailto: pbristow_at_[hidden]