Re: [boost] [review] Multiprecision review (June 8th - 17th, 2012)

Subject: Re: [boost] [review] Multiprecision review (June 8th - 17th, 2012)
From: Steven Watanabe (watanabesj_at_[hidden])
Date: 2012-06-29 15:42:41

AMDG

On 06/25/2012 10:44 AM, John Maddock wrote:
>> 
>> * line 423: (std::numeric_limits<T>::digits + 1) * 1000L
>>  This limits the number of bits to LONG_MAX/1000.
>>  I'd like there to be some way to know that as
>>  long as I use less than k bits, the library
>>  won't have any integer overflow problems.  k
>>  can depend on INT_MAX, LONG_MAX, etc, but the
>>  implementation limits need to be clearly documented
>>  somewhere.  I really hate the normal ad hoc
>>  situation where you just ignore the problem and
>>  hope that all the values are small enough to avoid
>>  overflow.
> 
> If there are really more digits than fit in a long then we'll likely
> have other issues - such as not enough memory to store them all in -
> however, I've added a static_assert and a note to this effect.
> 

Taking into account the fact that
numeric_limits::digits is in bits
and the extra factor of 1000, it
only takes 500 KB to run into a
problem when long is 32 bits.  This
is small enough that running out
of memory is not necessarily an issue.

In Christ,
Steven Watanabe