[Beowulf] Re: Redmond is at it, again

[C J Kenneth Tan -- OptimaNumerics]

On 2004-06-10 11:36 -0400 Robert G. Brown (rgb at phy.duke.edu) wrote:

> Date: Thu, 10 Jun 2004 11:36:09 -0400 (EDT)
> From: Robert G. Brown <rgb at phy.duke.edu>
> To: Suvendra Nath Dutta <sdutta at cfa.harvard.edu>
> Cc: douglas at shore.net, beowulf at beowulf.org
> Subject: Re: [Beowulf] Re: Redmond is at it, again
> 
> On Thu, 10 Jun 2004, Suvendra Nath Dutta wrote:
>
> > I know you say for the most part, but I think this is a perception that 
> > we should really look at. Prof. Edelman was really able to challenge 
> > this perception with his MATLAB*P. The notion is that MATLAB's 
> > implementation of LAPack is really excellent. So if used judiciously 
> > (especially as a set of mathematical libraries rather than a scripting 
> > engine) it can be faster than most direct implementation of code 
> > written in C/C++.
> 
> Now really, how can that be?  After all, it is just a library, written
> in all probability in C and linked to matlab so that matlab calls can
> execute the library functions.  matlab itself is likely written in C or
> C++.  Matlab's data structures are almost certainly going to be accessed
> through a higher degree of indirection than data structures one might
> create inside a dedicated function program, and data access speed alone
> can improve by 10-20% from that.  

This is a typical example of one implementation of LAPACK is not equal
to another implementation of LAPACK.  

> Finally, in C one can implement linear algebra code in particular
> using ATLAS, which can all by itself speed operations up by as much
> as a factor of three.

ATLAS != LAPACK.  ATLAS == BLAS + (LU code) + (full storage Cholesky code). 


Kenneth Tan
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