Re: [boost] serialization support for std::complexandboost::ublas::vector

From: Robert Ramey (ramey_at_[hidden])
Date: 2005-08-26 15:21:37

Neal Becker wrote:
> Robert Ramey wrote:
>
>> A couple of questions/observations:
>>
>> a)
>> ...
>>> template<typename Archive, typename T>
>>> inline void save (Archive &ar, const std::complex<T>& z, const
>>> unsigned int) {
>>>  ar << real (z);
>>>  ar << imag (z);
>>> }
>>
>> I presume that real imag return either primitives(float or double) or
>> references to these.   So that tracking would not be an issue.
>>
>>>
>>> template<typename Archive, typename T>
>>> inline void load (Archive &ar, std::complex<T>& z, const unsigned
>>>  int) { T i, r;
>>>  ar >> r;
>>>  ar >> i;
>>>  z = std::complex<T> (r, i);
>>> }
>>
>> Hmm, loading to a temporary and then moving to a final destination
>> could create an issue with tracking.  There are a couple of
>> possibilities:
>>
>> * if real/imag return references, then reformulate the above to:
>>     ar >> real(z);
>>     ar >> imag(z);
>> since this is now symetric with the save one could avoid the split
>> entirely and simplify it even more.
>>
>> * use reset_object_address
>
> You and I both wish real() and imag() returned a ref!!! But they
> don't.
>
> So I have:
> template<typename Archive, typename T>
> inline void load (Archive &ar, std::complex<T>& z, const unsigned
>  int) { T i, r;
>  ar >> boost::serialization::make_nvp ("real", r);
>  ar >> boost::serialization::make_nvp ("imag", i);
>  z = std::complex<T> (r, i);
> }
>
> Now how can I use reset_object_address, now that the the addresses of
> the real and imag pieces of the constructed object are no longer
> accessable?

Looking at this more carefully, and realizine that real and imag return 
values rather than references, I think I gave the wrong answer.

inline void load (Archive &ar, std::complex<T>& z, const unsigned int) {
    T i, r;
    ar >> boost::serialization::make_nvp ("real", r);
    ar >> boost::serialization::make_nvp ("imag", i);
     z = std::complex<T> (r, i);
}

I think the above will work just fine.  The address being tracked is that of 
z so I expect that this will work exactly as one would expect.  The saving 
would be exactly as you had it before.

The only remaining question is what serialization traits - if any - should 
be assigned to std::complex<T>.  Tracked/non-tracked.  implementation 
level - primitive, object, with class-id, etc.  My guess would be

non-tracked
primitive

as that would more closely fit with other types such as float etc.  I see no 
reason why any class version needs to be stored either.

Robert Ramey