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Re: Multithreading [message #29851 is a reply to message #29721]

Thu, 21 March 2002 02:42

weitkamp
Messages: 33
Registered: October 1998

Member

the_cacc@hotmail.com (trouble) wrote in message news:<5f9f0a23.0203200332.3d1e3fbf@posting.google.com>...
>
> [...]
>
> Yeah, read it. Just suprised no-one "real" is raving about their performance gains.

Not much to rave about in my case. I mostly do two kinds of
numbercrunching. One is Fresnel wave propagation, where the essential
operations are FFTs of arrays of size between 1024^2 and 4096^2
pixels. The other is tomographic reconstruction using the RADON
function (new in 5.4). I've not had the time to do any systematic
investigation on 5.5's multithreading behavior, but here is my
experience so far:

For the 2D FFTs, IDL does multithreading, but without a substantial
gain in time. Could even be that it takes longer with 5.5 (I tried the
same thing with 5.4 and 5.5, the latter being roughly 15 percent
faster, but on a CPU with higher clockspeed). Sorry I can't give
figures on that and haven't yet tried both 5.4 and 5.5 with the same
task on the same machine (had no time) --- I'd be among those who will
appreciate if someone else does.

For the backprojection, RADON does not multithread at all (I try this
with 2048x2048 slices and 1250 projections for each slice). Given that
backprojection is an application where the layman suspects that
multithreading should be relatively easy to implement, I was certainly
disappointed by that. Seems to be a very commercial decision in that
there's definitely more people use FFT than backprojection, and those
who don't use any of the two have at least heard about Fourier
transforms.

Cheers,

Timm

Timm Weitkamp
European Synchrotron Radiation Facility (ESRF), Grenoble, France

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[Message index]

		Re: Multithreading By: the_cacc on Wed, 20 March 2002 03:32
		Re: Multithreading By: Rick Towler on Tue, 19 March 2002 12:35
		Re: Multithreading By: Karl Schultz on Tue, 19 March 2002 06:49
		Re: Multithreading By: the_cacc on Tue, 19 March 2002 03:01
		Re: Multithreading By: Rick Towler on Fri, 15 March 2002 17:09
		Re: Multithreading By: Ralf Flicker on Thu, 14 March 2002 12:00
		Re: Multithreading By: weitkamp on Thu, 21 March 2002 02:42

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