dolfin team mailing list archive

[A Navaei <axnavaei@xxxxxxxxxxxxxx>]

2009/3/23 Matthew Knepley <knepley@xxxxxxxxx>:
> On Mon, Mar 23, 2009 at 9:47 AM, A Navaei <axnavaei@xxxxxxxxxxxxxx> wrote:
>>
>> 2009/3/23 Matthew Knepley <knepley@xxxxxxxxx>:
>> > I am going to agree with Garth here. There is no real difference. MTL4
>> > uses the template engine to generate code. FFC uses Python. However,
>> > both approaches only generate C++ code. They can be made equivalent
>> > for any given problem. I am fairly sure the MTL guys would agree. I know
>> > them very well.
>>
>> If you want to have a runtime code-generator which implements the
>> features of compile-time template meta-programming one by one, such as
>> loop unrolling, and in this way effectively end up with an equivalent;
>> then the question is why re-inventing the wheel?
>
> Template programming is awful. I have done a lot of it. The programming
> constructs that generate efficient code are non-intuitive and just about
> undebuggable. This is the whole point behind conceptGCC (also by the MTL
> guys). Templates are good at some jobs, but very very bad at others.

Do you believe that these disadvantages are also applied to MTL?


-Ali

>
>   Matt
>
>>
>> The compile-time has the benefit of avoiding double-compilation (lib +
>> jit) and implementing a code generator. Whether the above concepts are
>> the same or not, my original question is still unanswered: what's the
>> benefit of FFC runtime code-generation over compile-time template
>> meta-programming? Note that the form DSL can be still used with the
>> latter approach and it's not specific to FFC.
>>
>>
>> -Ali
>>
>> >
>> >    Matt
>> >
>> >>
>> >> -Ali
>> >>
>> >> >
>> >> > Garth
>> >> >
>> >> >> Without having a concrete meta-programming implementation, it may be
>> >> >> impossible to predict how much performance one would gain compared
>> >> >> to
>> >> >> FFC. However, MTL4 has been reported to be many times faster than
>> >> >> code-generation means such as ATLAS.
>> >> >>
>> >> >> Based on this, are there any specific benefits in FFC
>> >> >> code-generation
>> >> >> which may not be covered by meta-programming?
>> >> >>
>> >> >>
>> >> >> -Ali
>> >> >> _______________________________________________
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>> >> >
>> >> >
>> >> >
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>> >
>> >
>> >
>> > --
>> > What most experimenters take for granted before they begin their
>> > experiments
>> > is infinitely more interesting than any results to which their
>> > experiments
>> > lead.
>> > -- Norbert Wiener
>> >
>
>
>
> --
> What most experimenters take for granted before they begin their experiments
> is infinitely more interesting than any results to which their experiments
> lead.
> -- Norbert Wiener
>