Re: Intel vs AMD

On 14/08/2012 9:00 a.m., Martin Johnson wrote: > Thanks for all your comments and now I understand that there could be always slight differences between different CPU/architecture. > > However, Would it possible that there could be differences in successful minimizations in nonmem runs. For example, for a same model, in one CPU/architecture the model run is minimized successfully with covariance step and in the other the run is terminated with rounding error. > > I would like to say that I have not faced this problem yet. Just a question, to learn from your experience. > > regards, > Martin > > On 08/13/2012 03:13 PM, Bob Leary wrote: > > > Even when using a non-Intel compiler (e.g. gnu compilers) with exactly the same compiler options and optimization levels on AMD and Intel that generates exactly the same code for both , there can be numerical differences between AMD and Intel processors. > > > > We did a study [1] on Phoenix NLME results using the gnu g77 compiler with different Intel processors and Windows operating systems going back to 2002 and up to current generation processors (i3/i5/i7) and Windows 7. We generally got bit for bit identical results across every system tested when the compiler settings were the same. But AMD processors gave slightly different results. I found an AMD technical manual that indicated the probable reason - it advised that the AMD 80-bit x87 math floating point unit can give slightly different results than the corresponding Intel FPU. > > > > Indeed, we have found this to be the case in practice. > > > > {1} R. Leary et al, "Exact Reproducibility of Population PK/PD MLME Numerical Results across Different Computational Environments", PAGE 2011 (abstract 2042]. > > > > -----Original Message----- > > > > From: [email protected] [ mailto: [email protected] ] On Behalf Of Nick Holford > > > > Sent: Sunday, August 12, 2012 4:56 PM > > To: nmusers > > Subject: Re: [NMusers] Intel vs AMD > > > > Mark, > > > > I think you may not be fully appreciating the terms of the agreement when you say "it is generally accepted that Intel continues to impair the optimization on AMD CPU".Under the terms of the agreement (which you provide below) it is perfectly OK for Intel to optimize their compilers for Intel CPUs without including any optimization for AMD CPUs. Furthermore they are not required to provide any optimization for AMD CPus. Therefore, unless Intel don't know how to optimize compilers you must expect the Intel compiler to perform better on an Intel CPU. > > > > This issue might (or might not) be relevant to Martin's query about 'differences'. He does not specify the kind of difference e.g. faster? more accurate?. It may be possible to choose compiler options that produce identical numerical results on both CPUs but at the price of speed. > > > > Rik Schoemaker suggested using these Intel compiler options /nologo /nbs /w /Gs /fp:strict to obtain consistent numerical results ( http://www.cognigencorp.com/nonmem/current/2011-May/3266.html ) with different NONMEM 7 versions across different operating systems. Perhaps these options would ensure numerical consistency across different CPU types. > > > > Best wishes, > > > > Nick > > > > On 13/08/2012 8:27 a.m., Mark Sale - Next Level Solutions wrote: > > > > > Martin > > > Yes, the results can be different. Intel has been accused of > > > "crippling" the executable when the Intel compiler is used on AMD CPUs > > > http://www.agner.org/optimize/blog/read.php?i=49 > > > > > > by turning off all optimization - they actually pretty much admitted > > > this in the lawsuit - but explained that it was for the benefit of the > > > customer - sort of like in the 1980's when Microsoft pretty much > > > disabled WordPerfect with every new OS release. > > > > > > and yes, different optimization setting will give different results, > > > 32 bit will also give different results from 64 bit. Sometimes the > > > phase of the moon, or the users astrological sign makes a different as > > > well ;-) Below is from the settlement: > > > Intel shall not include any Artificial Performance Impairment in any > > > Intel product or require any Third Party to include an Artificial > > > Performance Impairment in the Third Party’s product. As used in this > > > Section 2.3, “_Artificial Performance Impairment_” means an > > > affirmative engineering or design action by Intel (but not a failure > > > to act) that (i) degrades the performance or operation of a Specified > > > AMD product, (ii) is not a consequence of an Intel Product Benefit and > > > (iii) is made intentionally to degrade the performance or operation of > > > a Specified AMD Product. For purposes of this Section 2.3, “_Product > > > Benefit_” shall mean any benefit, advantage, or improvement in terms > > > of performance, operation, price, cost, manufacturability, > > > reliability, compatibility, or ability to operate or enhance the > > > operation of another product. > > > > > > In no circumstances shall this Section 2.3 impose or be construed to > > > impose any obligation on Intel to (i) take any act that would provide > > > a Product Benefit to any AMD or other non-Intel product, either when > > > such AMD or non-Intel product is used alone or in combination with any > > > other product, (ii) optimize any products for Specified AMD Products, > > > > > > or (iii) provide any technical information, documents, or know how to AMD. > > > > > > But, it is generally accepted that Intel continues to impair the > > > optimization on AMD CPU. > > > So, to answer your question, I don't think there is any way to insure > > > consistent results between Intel and AMD CPUs. > > > > > > Mark > > > > > > Mark Sale MD > > > President, Next Level Solutions, LLC > > > http://www.NextLevelSolns.com > > > 919-846-9185 > > > A carbon-neutral company > > > See our real time solar energy production at: > > > http://enlighten.enphaseenergy.com/public/systems/aSDz2458 > > > > -- > > Nick Holford, Professor Clinical Pharmacology > > > > First World Conference on Pharmacometrics, 5-7 September 2012 Seoul, Korea http://www.go-wcop.org > > > > Dept Pharmacology& Clinical Pharmacology, Bldg 505 Room 202D University of Auckland,85 Park Rd,Private Bag 92019,Auckland,New Zealand > > > > tel:+64(9)923-6730 fax:+64(9)373-7090 mobile:+64(21)46 23 53 > > email: [email protected] > > http://www.fmhs.auckland.ac.nz/sms/pharmacology/holford > > > > _________________________________________________________________ > > > >