RE: [Caml-list] Pointers needed for optimization problem.

["Gurr, David (MED, self)" <David.Gurr@med.ge.com>]

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>From the FFTW web page <<http://www.fftw.org/download.html>>:

fftwgel
fftwgel <<http://www.complang.tuwien.ac.at/skral/fftwgel.html>> is an
experimental version of fftw with support for the SIMD instructions of
the AMD K6-2 and K7 processors as well as the Intel Pentium IV, written
by our colleague Stefan Kral at the Vienna University of Technology. We
hope to incorporate a generalization of this work into a future version
of FFTW. 

fftwgel has ocaml code for generating SIMD code for x86 machines.  Other
key words
are SWAR and Atlas.  Plus the intel and amd web pages have lots of info.
-D

> -----Original Message-----
> From: Pal-Kristian Engstad [mailto:engstad@naughtydog.com]
> Sent: Wednesday, August 21, 2002 7:33 PM
> To: caml-list@inria.fr
> Subject: [Caml-list] Pointers needed for optimization problem.
> 
> 
> Hi,
> 
> I'm interested in solving a problem I have with automatically 
> generating 
> optimal (vector) floating point code. In other words, I want 
> to code a caml 
> program that transforms the input description into assembly 
> instructions. For 
> regular floating point operations, a good compiler should be 
> able to optimize 
> the code:
> 	
> 	r := A * x * x + B * x + C
> 
> into (if multiplication is more expensive than adds):
> 
> 	t := A * x
> 	t := t + B
> 	t := t * x
> 	t := t + B
> since
> 	r := (A * x + B) * x + C
> 
> Now, this is fairly trivial to do, but if you have an 
> architecture with SIMD 
> vector floating point registers and opcodes, a whole range of 
> new interesting 
> optimizations can be done. With vector registers, I mean 
> registers that have 
> up to 4 floating point values. For instance, a 4-vector times 
> a 4-by-4 matrix 
> operation can be coded as:
> 
> 	acc.xyzw := mtxrow[0].xyzw * vec.x
> 	acc.xyzw += mtxrow[1].xyzw * vec.y
> 	acc.xyzw += mtxrow[2].xyzw * vec.z
> 	res.xyzw = acc.xyzw + mtxrow[3].xyzw * vec.w
> 
> Here, each line represent one assembly instruction.
> 
> So, what I am looking for is basically pointers to literature 
> that deal with 
> issues like these, and since OCaml is a great language for language 
> transformations I thought someone on this list would be able 
> to point me in 
> the right direction. I _have_ been searching on the net, but 
> I guess I don't 
> know the right keywords to search on.
> 
> PKE.
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