Re: [ublas] [bindings] Workspaces

Subject: Re: [ublas] [bindings] Workspaces
From: Karl Meerbergen (Karl.Meerbergen_at_[hidden])
Date: 2008-12-15 04:09:48

Thomas Klimpel wrote:
> Rutger ter Borg wrote:
>   
>> I agree. Whatever interface we end up with, if a user can pass
>>
>> lapack::function( ..., optimal_workspace() );
>> lapack::function( ..., minimal_workspace() );
>> lapack::function( ..., workspace( a ) );
>> lapack::function( ..., workspace( a, b ) );
>> lapack::function( ..., workspace( a, b, c ) );
>>
>> would be clean and consistent to me.
>>     
>
> This is indeed clean. I can see the big picture now.  Instead of
>
>   
>>     /// Select the number of workspaces depending on the value_type
>>     template <typename T>
>>     struct n_workspace_args { };
>>     
>
> we simply need a compile time way to tell whether a value_type is
> actually a complex value_type. The simplest way to achieve this would
> probably be to extent the type_traits traits struct/class by a "static
> const bool is_complex = false ;" member. The template function
> template<typename A, typename B, typename C> XXX workspace(A& a, B& b,
> C& c) could then simply return a XXX=boost::tuple<A&, B&, C&>.
>   

I do not think type_traits should be extended. I hope to make a proposal
this week.

Best regards,

Karl

>
> Karl Meerbergen wrote:
>   
>>> We might also consider to make the
>>> order of arguments passed to workspace arbitrary, by adding
>>>       
> different
>   
>>> retrieve methods for each value_type into the workspace1 ...
>>>       
> workspace3
>   
>>> classes.
>>>   
>>>       
>> I have thought of that. Since the value_type of the arrays are fixed 
>> anyway that should be quite easy to do.
>>     
>
> It may be easy to do (if you know how to do it), but I'm not sure
> whether this is really worth it. It's certainly no major restriction to
> the user if he has to provide the workspace arguments in the same order
> as the corresponding lapack routine (i.e. complex first, then real, and
> then integer).
>
>
> Karl Meerbergen wrote:
>   
>> Yesterday, I suggested to add workspace3. No reactions so far. I have
>> started the implementation in boost.sandbox, but I want agreement with
>> the ml before continuing.
>>     
>
> I really like the proposed 
>
> optimal_workspace()
> minimal_workspace()
> workspace( a )
> workspace( a, b )
> workspace( a, b, c )
>
> semantic. Whether workspace( a, b, c ) returns a boost::tuple<A&, B&,
> C&> or a workspace3<A,B,C> (or something completely different) is less
> important to me. Just to be clear, workspace( a, b ) would return
> boost::tuple<A&, B&> or a workspace2<A,B> and workspace( a ) would
> return  boost::tuple<A&> or a workspace1<A>.
>
> Regards,
> Thomas
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