SETI@home now supports Intel GPUs


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Profile Raistmer
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Message 1504303 - Posted: 15 Apr 2014, 8:41:28 UTC - in response to Message 1503216.
Last modified: 15 Apr 2014, 8:42:10 UTC

You've got it backwards. Calibrating for the best optimized version reduces the credit grants for all versions and penalizes optimizations. Calibrating for the worst increases the credit grants for all versions.


It what discussed already - it's counter-productive for stock optimization.
and no, we never calibrated on anynymous platform app. And stock app never was fastest.
Credit will be reduced if stock will not be changed to include already implemented optimizations. Hence pressure from credit system to make stock efficient.
Currently we see big disagreement between MB and AP credit. Why?
Because stock MB is quite optimised app and stock AP... well, I will be polite :).
Hence huge overpay for both CPU opt AP and GPU AP both stock and opt.
The same with other projects. If some project has crappy app and some releases adequately optimized app then almost all go to anonymous platform and enjoy enormous credits. And server ignores times from anonymous platform so no re-calibration happens. That's how it works now.
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Message 1504312 - Posted: 15 Apr 2014, 9:00:23 UTC
Last modified: 15 Apr 2014, 9:01:05 UTC

To sacrify project performance for pleasing credit system? Well, I would not consider it as good move.
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Message 1504417 - Posted: 15 Apr 2014, 19:15:34 UTC - in response to Message 1504200.

So if they are on CreditNew they need to keep the slowest app for 'calibration'? ;)

Yes, actually. If the speed difference is large (and if the server works as advertised) then the slow version should be sent only very rarely.

Of course the second part of that if is the hard part.

The assumption of course, is that a slow app is representative of the benchmark speeds. Of course, that's never the case. The benchmarks will always be faster than any real single threaded SISD app. That's what the old "credit multiplier" was for.
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Message 1505387 - Posted: 17 Apr 2014, 22:44:08 UTC - in response to Message 1504417.
Last modified: 17 Apr 2014, 22:48:12 UTC

The assumption of course, is that a slow app is representative of the benchmark speeds. Of course, that's never the case. The benchmarks will always be faster than any real single threaded SISD app. That's what the old "credit multiplier" was for.


Hmmm, yeah. Whetstone should be defeating certain compiler optimisations by design, but likely not pressure the memory hierarchy much (if at all). That would, for old FPU at least, place real dataset size processing throughput much lower, closer to memory bandwidth minus stalls, due to small caches, some unfavourable access strides, and limited prefetch capability except where hardcoded. On the other hand since memory speed back then was relatively closer to CPU core speed (fewer cache levels needed), that was probably slightly fairer from one angle.

Anyway I suppose it's all another take-away indicator, Boinc Whetstone might not have been the right choice even for pre-SIMD (Which I hadn't considered yet).

Well at least we know pfc_scale and host_scales reach impossibly low values for genuine reasons. I guess poking this many holes in the basic scaling should result in fair solutions arriving eventually.

For the time being I'm still of the opinion that if scale < 1 then it indicates parallelism ( of either SIMD or mis-summed multithreading form ) which could then be inverted. That would have effects of declaring original estimates as a minimum possible (which it is here), and converge on the cobblestone scale, but I'm certain there are angles I haven't though of yet.

I'm not sure taking the scaling reference from server side & placing it on the quite jiggerable Boinc Whetstone was a good move, despite that I guess the intent would have been to compensate for really bad initial estimates at various projects. The instabilities are something I can certainly help fix, but the base scaling would require decisions as to which end is 'more right'. Here I believe the fpop estimates are relatively good, compared to the proportion of erratic behaviour in other areas.
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"It is not the strongest of the species that survives, nor the most intelligent that survives. It is the one that is the most adaptable to change."
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Message 1525232 - Posted: 6 Jun 2014, 15:34:19 UTC

I'm quite happy with my crunching Intel GPU, haven't encountered any issues yet.
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Message boards : News : SETI@home now supports Intel GPUs

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