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Re: Speed of Mathematica on AMD machines
On Sat, 12 May 2012 09:51:17 +0100, A Retey <awnl at gmx-topmail.de> wrote: > > Hi, > >> In the past, Intel had been known to engage in anticompetitive practices >> with respect to AMD, and quite rightly was subject to legal penalties >> for >> this. (Specifically, they encouraged large computer manufacturers such >> as >> ... >> which both show that Bulldozer performance is a very mixed bag in >> general. >> While there are a few applications in which it can match or only just >> outperform Intel's offerings, for the most part it falls behind them >> considerably. > > Very good points, Oleksandr, I agree with everything except that you > could argue just as well that the the performance of intels processors > is a mixed bag, after all they could be expected to be faster where > Bulldozer matches or outperforms them. > Technically that's true, although I think a factor worth considering is that Sandy Bridge and Bulldozer are not exactly contemporaneous. Sandy Bridge was launched in January 2011, while Bulldozer didn't come along until October of the same year. Recently Intel has released Ivy Bridge which improves again on Sandy Bridge performance (in general, but especially in respect of graphics). > I think the point is that processors (and more important: bundles of > hardware+OS+software) _are_ different and there is not a single number > which you can reliably use to compare them -- your best deal depends on > what exactly you are doing. That's not a very new finding though, you'll > find that conclusion everywhere (actually whether that conclusion is > made is a good measure of quality and impartiality of what you read). > I agree and will confess to being biased toward scientific and HPC benchmarks as I think that these are some of the only ones for which more performance still really matters for the average user (of these sorts of applications, which is admittedly a very small segment of the market as a whole). Compiling code is another example. Consumers in general are more sensitive to performance in mass-market applications such as media encoding/decoding and videogames. For symbolic computations in Mathematica we need large, fast caches and good performance in single-threaded integer workloads (characteristics that are shared by code compilation and videogames), and for numerical computations good memory bandwidth and multithreaded floating-point performance are called for (in common with HPC workloads and to some extent video encoding). In both cases Intel processors are a better match for Mathematica's requirements than AMD processors, which are more optimized for throughput in multithreaded integer workloads (although, if you make extensive use of the Parallel` package, AMD processors may be much more attractive). > If you really try to find the optimal deal that's a tough job, and I > think even experts can't do reliable forecasts without some > experimentation on the real thing. Fortunately processors are so fast > nowadays that you can get done quite a lot even with a poor choice... > I would definitely advocate doing your own benchmarks, but the specific ones mentioned by Dmitry are not likely to be very representative of general usage. MathematicaMark is not too bad, although I think it would be substantially improved by including some more involved tests such as integration, equation solving, expression simplification, numerical optimization, code compilation, plotting data and functions, and so on alongside the rather simple operations that make up the existing benchmark. In terms of representativeness, there is of course no substitute for benchmarking your own code. It is also very important to consider the ratio of performance/price, if cost is a factor. By this metric the AMD processors do not look as poor as they do when considering absolute performance. Power consumption is another relevant metric in many cases but AMD is again usually behind Intel here. Best, O. R.