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Glas :Re: [glas] dotc and dotu in glas |
From: Karl Meerbergen (Karl.Meerbergen_at_[hidden])
Date: 2006-05-02 04:14:00
Removing ambiguity is a strong argument for having two different
functions, dotc() and dotu().
Karl
Sanz, Christophe wrote:
>Quoting Karl Meerbergen <Karl.Meerbergen_at_[hidden]>:
>
>
>
>>As far as I understand, Toon was talking about core syntax, not
>>functionality:
>>is there a problem with dot(conj(x),y) for the euclidean inner product?
>>
>>Karl
>>
>>
>>
>
>Possibly not but there seem to remain some ambiguity pertaining to the choice of
>the proper specialisation of the dot function for collection of complex types.
>The maths would suggest that it is dotc while (eg:) the MTL would suggest that
>it is dotu. Possibly the latter option was just too straightforward to be
>avoided in first place but retaining option 1 could be well worth a
>confirmation. Was that Matthias meant?
>
>
>>Matthias Troyer wrote:
>>
>>
>>
>>>I want to strongly support Andrew's statement. If one wants only one
>>>dot product then the proper inner product for a complex Hilbert space
>>>needs to be chosen.
>>>
>>>Matthias
>>>
>>>On May 1, 2006, at 10:59 AM, Andrew Lumsdaine wrote:
>>>
>>>
>>>
>>>
>>>
>>>>Both are needed.
>>>>
>>>>In the Iterative Template Library, both are required in order for the
>>>>solvers to work properly with complex vectors.
>>>>
>>>>Mathematically, dotc() is a proper inner product for a complex Hilbert
>>>>space, dotu() is not. If a single dot() function is going to be used
>>>>for inner product, mathematically it must be equivalent to dotc().
>>>>
>>>>Use cases are very important when creating interfaces for a generic
>>>>library. I would suggest taking a look at ITL and IETL to see how
>>>>generic linear concepts at this level of abstraction are used.
>>>>
>>>>Toon Knapen wrote:
>>>>
>>>>
>>>>
>>>>
>>>>>I was wondering if we need an equivalent for both the dotc and
>>>>>dotu of
>>>>>BLAS in glas? I suggest to only have _one_ dot function (which is
>>>>>equivalent to the dot in blas for vectors of reals and which
>>>>>corresponds
>>>>>to dotu for vectors of complex values). To perform the equivalent of
>>>>>dotc one could then write dot(conj(x),y). This is IMHO clearer and
>>>>>the
>>>>>expression-template mechanism will avoid that this compound
>>>>>expression
>>>>>will induce a performance penalty.
>>>>>
>>>>>I just added an equivalent to dotc but I plan to add the solution as
>>>>>described above, benchmark both and than remove the dotc equivalent
>>>>>afterwards (supposing the benchmark will not show any performance
>>>>>differences of both approaches).
>>>>>
>>>>>toon
>>>>>
>>>>>
>>>>>_______________________________________________
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>>>>>glas_at_[hidden]
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>>>>>
>>>>>
>>>>>
>>>>>
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>>>>
>>>>
>>>>
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>>>
>>>
>>>
>>>
>>--
>>==============================================
>>Karl Meerbergen
>>
>>Free Field Technologies
>>
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>>
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>>rue Emile Francqui, 1
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>>============================================
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>>
>>
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>>
>>
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>
-- ============================================== Karl Meerbergen Free Field Technologies NEW ADDRESS FROM FEBRUARY 1st ONWARD: Axis Park Louvain-la-Neuve rue Emile Francqui, 1 B-1435 Mont-Saint Guibert - BELGIUM Company Phone: +32 10 45 12 26 Company Fax: +32 10 45 46 26 Mobile Phone: +32 474 26 66 59 Home Phone: +32 2 306 38 10 mailto:Karl.Meerbergen_at_[hidden] http://www.fft.be ============================================