Re: [Boost-users] uBLAS, Inverse of Matrices -- Urgent

From: Hossein Haeri (powerprogman_at_[hidden])
Date: 2005-01-25 05:25:46

Andrew,

> The purpose of Policy-Based Design, as I understand
> it, is to cleanly
> separate mechanism and policy, even in places where
> mechanism needs to
> call on policy.  In the case of inverting matrices,
> policy can be
> perfectly well implemented as a layer above (e.g.
> LAPACK), so BLAS
> doesn't need to know about it.

Seems perfectly reasonable.

> BLAS officially stands for Basic Linear Algebra
> Subprograms.  A little
> history might help here.  (Note: I've taken
> liberties with the "history"
> that follows, because I'm not a historian and the
> purpose of what follows
> is not to be an accurate chronicle, but rather to
> talk about the purpose
> of BLAS.)

I see.

> BLAS dates from the early days of numeric
> supercomputing.  Supercomputers
> have various capabilities (vector pipelines and so
> forth) which are not
> easily used by a compiler for a general-purpose
> language like Fortran.  A
> lot of research has gone into automatically finding
> opportunities to use
> these hardware features with varying degrees of
> success, but no real
> guarantees.
> 
> So rather than wait for Sufficiently Smart Compilers
> to appear, people
> used a standard library instead.  This library is
> BLAS.  Supercomputer
> vendors might ship their own version BLAS, tuned to
> take advantage of the
> available hardware and do the rest in software.
> In other words, BLAS is really, really Basic.

And that's basic in the sense of algorithms, not the
sense of linear algebra. I think, I got it. Thanks! :)

Sorry, I'm in a hurry for going lunch. I'll be back
afterwards.

Best Wishes,
--Hossein

        
        
                
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