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Blitz Support : |
From: Todd Veldhuizen (tveldhui_at_[hidden])
Date: 2003-10-12 11:49:40
Hi Roger,
Could you post an example of the kind of iteration you'd like to do,
(i.e. an excerpt of M++ code)?
Regarding BLAS, does your code spend a substantial amount of time in an
array operation that corresponds to a BLAS routine? Blitz++ is designed to
get decent performance for any array expression, whereas BLAS provides a
selected set of fast implementations of common expressions in linear
algebra. The idea of invoking BLAS from blitz when possible has been
kicked around, but so far it seems like nobody has had their code run
unacceptably slow because BLAS isn't used (or, they've been willing
to grab pointers and invoke blas themselves.) I guess it just hasn't
seemed worth the effort to anyone to write the BLAS hooks.
Cheers,
Todd
On Fri, 10 Oct 2003, roger.grant wrote:
> I am currently using the M++ package on Windows. I am transferring my work to FreeBSD and the M++ is not easily changeable to go to a UNIX environment and is also of very old technology as compared to Bltz++. Anyway, M++ defines an Index as a class and I am able to define a special index which I will call a Leave-One-Out index. I can then transverse my array iteratively leaving one out.
> Example:
> Define a Vector of 100 items.
> define a leave-one-out index which will be of size 99.
> pass thru the Vector 100 times; each time leaving out a different point ( from 0 to 99)
> This is VERY useful for working to develope pattern matching algorithms as you never use the point that you are trying to predict within the algorithm. My software may make 1000's of passes on the Vector/Array working to optimize the algorithm, to minimize the "error". The Vector/Array is only created once and only the "view" of the data is changed.
> How can I accomplish this with Blitz++???
> Thank You!
> Roger Grant
> PS: I am surprised that you do not use the blas libraries. Wouldn't this lead to a severe performance hit as most architectures have optimized assembler coded blas?
>
-- Todd Veldhuizen / tveldhui_at_[hidden] / Indiana University Computer Science