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* [Caml-list] FP's and HyperThreading Processors
@ 2003-06-13  6:44 David McClain
  2003-06-13  8:06 ` John Max Skaller
                   ` (2 more replies)
  0 siblings, 3 replies; 17+ messages in thread
From: David McClain @ 2003-06-13  6:44 UTC (permalink / raw)
  To: caml-list

Hi,

I have a massive application that performs nonlinear fitting to 170+
parameters; a phase retrieval problem for discerning the aberrations of an
optical system. This program is written largely in compiled OCaml closures,
along with a multithreaded vendor supplied FFT routine (presumably optimized
for their processor).

On an old P2 single processor machine at 350 MHz, I am seeing almost 95%+
CPU utilization. But on a new 3 GHz P4 with HyperThreading enabled (dual
register banks for fast context switching and minimum cache coherence
overhead), this same program provides much less than 5% CPU utilization. The
net result is that this program runs only twice as fast on the new 3 GHz P4
as it runs on the old 350 MHz P2.

I suspect, but have yet to prove, that the low utilization is due to a low
CPU to memory bandwidth and to the failure of the L1 and L2 caches to supply
needed operations and data to the CPU. This, I would hypothesize, is going
to be demonstrated by any language that prefers fresh memory allocation for
results, e.g., OCaml, ML, Lisp, Smalltalk, etc.

If I am correct, then it implies that our hardware friends are moving
rapidly in the opposite direction to our advanced software systems. I
mention this in order to tickle the imaginations of both camps.

Cheers,

- David McClain, Sr. Scientist, Raytheon, Tucson, AZ


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^ permalink raw reply	[flat|nested] 17+ messages in thread

end of thread, other threads:[~2003-07-02 10:26 UTC | newest]

Thread overview: 17+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2003-06-13  6:44 [Caml-list] FP's and HyperThreading Processors David McClain
2003-06-13  8:06 ` John Max Skaller
2003-06-13 10:03   ` [Caml-list] Type safe affectation ? Christophe Raffalli
2003-06-14 13:35     ` Xavier Leroy
2003-06-15 18:53       ` brogoff
2003-06-15 19:49         ` Brian Hurt
2003-06-16  1:38           ` Jacques Garrigue
2003-06-13 18:38 ` [Caml-list] FP's and HyperThreading Processors Kip Macy
2003-06-13 21:23   ` David McClain
2003-06-13 21:39     ` Kip Macy
2003-06-13 21:56       ` David McClain
2003-06-14 22:08         ` John Max Skaller
2003-06-14  6:11     ` Ville-Pertti Keinonen
2003-06-13 19:07 ` Xavier Leroy
2003-06-13 21:33   ` Jim Farrand
2003-06-13 21:39     ` David McClain
2003-07-02 10:26   ` David Monniaux

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