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AMD optimized App
KarVi:
I have not ignored anything. But still there is and have never been AMD only builds.
I will let the matter rest, since it is obviously of little importance. The most important thing is to get well optimized code that is compatible with official SETI code out the door.
I will continue to run tests and so on if this is wished, otherwise tell me so.
Jason G:
And neither will there be Intel only builds (apart from the obvious SSSE3, SSE4.1, and likely SSE4.2).
I will pass your comments onto the testing committee to assess whether your subjectiveness has compromised your value as tester.
Jason
Gecko_R7:
--- Quote from: KarVi on 18 Jan 2009, 02:27:59 pm ---That wouldn't help me any, since I can't read code.
You seem to be annoyed of me posting my worries. I don't understand the reaction. Though I may seem to be criticizising, my hope is to be helpfull and constructive.
There have been several Intel only builds, what would be wrong with an AMD only build? Do you use "prefetchw", and if you do, does it take the larger L1 cache into account? How about looking into SSE4a, or some of the 3DNow! instructions. Perhaps and only perhaps, one or two of the instructions therein could be of benefit?
Would you agree that the possibility exists that different code paths than the ones used, could perform better on AMD hardware? Why not try? This is only a suggestion, if the workload needed to create these builds, is of such magnitude that it would be counterproductive for the general optimization, it should just be left alone.
--- End quote ---
Different devs have looked at (& continue to do so) opportunites where AMD could uniquely benefit. The short answer is that in almost all cases, the work required would neccessitate complete re-writes of areas to benefit only "certain" AMD rigs.
A key developer who is on hiatus ATM (not active @ Lunatics BTW) recently commented that to do AMD correctly, would neccesate a COMPLETE re-write of the applications....from scratch. He also acknowledged the amount of time required vs. number of users that would benefit from this wouldn't justify the effort, unless that was the person's only interest and motivation.
It's not an issue of lack of respect, it's an issue of lack of resources and the overall challenges of resource allocation against several other considerations, application-types and prevalent platform combinations.
KarVi:
Thanks for the reply. Explains a lot.
Raistmer:
--- Quote from: KarVi on 18 Jan 2009, 02:27:59 pm ---That wouldn't help me any, since I can't read code.
You seem to be annoyed of me posting my worries. I don't understand the reaction. Though I may seem to be criticizising, my hope is to be helpfull and constructive.
There have been several Intel only builds, what would be wrong with an AMD only build? Do you use "prefetchw", and if you do, does it take the larger L1 cache into account? How about looking into SSE4a, or some of the 3DNow! instructions. Perhaps and only perhaps, one or two of the instructions therein could be of benefit?
Would you agree that the possibility exists that different code paths than the ones used, could perform better on AMD hardware? Why not try? This is only a suggestion, if the workload needed to create these builds, is of such magnitude that it would be counterproductive for the general optimization, it should just be left alone.
--- End quote ---
I'll try to give one more answer:
Regarding AstroPulse:
1) There is no Intel-specific build still. Any "specific" build requires additional efforts. General optimisation (if possible) gives MUCH MORE feedback because it's GENERAL. So, AP still has mostly general optimization.
2) It's tru that SSE3 MB builds work sometimes even slower on AMD than SSE2 ones. Sorry, but I see only poor SSE3 implementation on chip here, not any plot against AMD.
3) There is no SSSE3 and up support for AMD but SSSE3 gives nice speedup for MB (again, it's just reality).
4) There is NO AMD optimizing compiler exist. Intel has its own compiler, AMD has no own compiler at all. Look on AMD pages, they recommend different third party compilers (Intel was included if I remember right). But to do build with new compiler requires additional efforts (as to do CPU specific optimization instead of general optimisation) for porting. For AP only transition from general purpose MS VC to ICC in progress and already we have some difficulties with performance. To do builds with some alternative (and not freely available) compilers - more time required that could be spend more effective to general optimization.
5) Sure it's possible to speedup current AP (or MB probably) builds specifically on AMD chips, but not our fault that latest Intel's CPU respond better on general optimizations that AMD (although for AMD Athlon XP speed improve was best for AP SSE BTW).
I hope it's more clear now "why not try".
(ADDON: Gecko_R7 explained it already indeed)
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