"Brian J. Beesley" wrote:
> Could I suggest that your figures may be a bit misleading. The point
> is that, when the remaindering operation kicks in, roundoff errors
> start to take effect & MacLucasUNIX generally restarts with the next
> higher FFT size. You should really be running at least 100 iterations
> to be sure that you have the appropriate FFT size for the exponent,
> and that the timing isn't distorted by not running any code needed to
> implement the remaindering operation.
I actually ran all tests (except for 332192831 - the 16M FFT was just
too slow :) for about 170 iterations, but just picked a single result.
Maybe the data would have been more meaningful if I'd left the exponent
out and just reported the FFT length.
> I find, running MLU on a Alpha 21164-533, 128K FFT works up to about
> exponent 2.35 million, & pro rata. MLU on a Sparc seems to be able to
> run a bit higher, somewhere around 2.45 million seems to be OK for a
> 128K FFT. Mind you, a Ultra IIi-300 is only about 0.4x the speed of a
> Alpha 21164-533, running MLU compiled using gcc 2.8.1 on both
> systems.
I've got static MLU ev5 and ev6 binaries if Linux can run them under
some sort of Digital Unix emulation. Might be interesting to see how
gcc 2.8.1 compares with DEC's C compiler.
Look at ftp://melanoma.cs.rmit.edu.au/pub/simonb/MLU-ALPHA.tar.gz for
the binaries.
> The timings I have - from complete double tests - are
> 128K FFT, 25000 iters/27 minutes = 0.065 sec/iter
> 256K FFT, 10000 iters/31 minutes = 0.186 sec/iter
> 512K FFT, 5000 iters/27 minutes = 0.324 sec/iter
No matter which way you look at it, the 21264 is fast :-)
> For short tests of 400 iterations (for QA testing) I've run lucdwt
> (from Richard Crandall's giantint package, with minor modifications
> to output) on exponents up to nearly 80 million i.e. 4096K FFT. This
> just about fitted into 256MB; I was unable to proceed to 8192K FFT
> since I have only 320 MB on my system (& can't justify buying any
> more - in any case, Prime95 v19 gives up at ~79,600,000). These tests
> were running at 90 to 100 iterations per hour for 4096K FFT. See
> ftp://lettuce.edsc.ulst.ac.uk/gimps/PrimeQA/QADATA.TXT
The file format seems to be
exponent,iter-count,residue,??,??
Does the "lucdwt" mean that lucdwt was used to generate the file (and
Prime95 is tested against it)? And what's the last field (which some
lines don't have)?
> BTW here in the UK you can purchase a complete Alpha 21164-533 system
> with a decent hard drive & 128MB RAM, preloaded with RedHat linux,
> for under 1500 pounds sterling.
A few of us Aussies recently purchased some PC164-500 motherboards
(500MHz 21164) for $US250 - easily the fastest computer I own now!
Simon.
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