On Fri, 7 Oct 2005, Jennifer Lai wrote: > Is FFT implemented in R takes advantage of multi-processors? > I ran this benchmark from from http://www.sciviews.org, and AMD Opteron > 2.2 GHz performs better than AMD Opteron 1.8 GHz on all test cases, > except FFT operation. > Both machines run same OSs (RedHat WS 3) and 2.2 GHz has more memory (2 > GB RAM) than 1.8 GHz (1 GB RAM). The only difference is that 1.8 GHz is > a dual-processor machine, and > 2.2 GHz is a single processor machine. Could this be the reason? > Does anyone has insights on this?
I am pretty confident that nothing in Unix-alike R is multi-threaded. (The Windows port is.) However, you can use some multi-threaded addons, e.g. a BLAS library. AFAIK those chips differ in more than just speed, including exact cache details. Other details of the CPU architecture are often more important than small differences in clock speed. Even small compiler differences can affect performance a lot. I would also caution aginst drawing any conclusions at all from this sort of `benchmark' (indeed, would say it was a misuse of the term). Fortunately the computer world has moved on to using realistic tasks as comparators. When we last had a large procurement (a many-processor system fufilled by Opterons) we used real data-analysis programs written in C++ and Java. The tenders managed a very surprising difference in throughput on apparently identical CPUs, and results even from the same tender on different models of Opteron did not scale even approximately with clock speed. In the end we learnt more about the support skills of the potential suppliers than about the optimized performance of their systems. -- Brian D. Ripley, [EMAIL PROTECTED] Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/ University of Oxford, Tel: +44 1865 272861 (self) 1 South Parks Road, +44 1865 272866 (PA) Oxford OX1 3TG, UK Fax: +44 1865 272595 ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
