Re: Intel vs AMD

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 > > _________________________________________________________________ >