On 18 Aug 99, at 13:37, Simon Burge wrote:
> % ./MacLucasUNIX -C -S 10 1400001
> speed: 10 iters in 0.152 seconds, 0.015 iters/sec (fft len 64k)
> % ./MacLucasUNIX -C -S 10 2900001
> speed: 10 iters in 0.362 seconds, 0.036 iters/sec (fft len 128k)
> % ./MacLucasUNIX -C -S 10 5800001
> speed: 10 iters in 0.782 seconds, 0.078 iters/sec (fft len 256k)
> % ./MacLucasUNIX -C -S 10 11600001
> speed: 10 iters in 1.777 seconds, 0.178 iters/sec (fft len 512k)
> % ./MacLucasUNIX -C -S 10 23200001
> speed: 10 iters in 4.606 seconds, 0.461 iters/sec (fft len 1024k)
> % ./MacLucasUNIX -C -S 10 46400001
> speed: 10 iters in 13.601 seconds, 1.360 iters/sec (fft len 2048k)
Interesting.
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 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.
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
(Ultra IIi-300, 256K FFT, 5000 iters/33 mins = 0.396 sec/iter)
512K FFT runs nicely in only 64MB, but 1024K wouldn't.
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
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. See http://www.compusys.co.uk/
(please forgive me for "advertising"; I have no connection to this
company except as a customer).
Regards
Brian Beesley
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