Re: Comparison of Mathematica on Various Computers

*To*: mathgroup at smc.vnet.net*Subject*: [mg64355] Re: Comparison of Mathematica on Various Computers*From*: Ronald Bruck <bruck at math.usc.edu>*Date*: Mon, 13 Feb 2006 03:15:20 -0500 (EST)*References*: <200602090745.CAA19418@smc.vnet.net> <200602100713.CAA15024@smc.vnet.net> <dsk8m8$i9l$1@smc.vnet.net> <dsmueo$da0$1@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

In article <dsmueo$da0$1 at smc.vnet.net>, albert <awnl at arcor.de> wrote: > Renan wrote: > > > On 2/10/06, fizzy <fizzycist at knology.net> wrote: > >> Can someone explain why AMD does so well on this test and Pentium does so > >> poorly by comparison?? > >> I am planning to buy a new computer and these tests seem to indicate > >> that a Mathematica user should buy an AMD machine. > > > > I'd guess that an Athlon 64 CPU is faster than a Pentium 4 > > (32-bit).(most AMD CPU's that I see in the benchmark are 64-bit) > > hm, I hoped for good answers to that, but my guess is also that it is the > 64-bit vs. 32-bit which explain the difference to a big extent. Obviously > it will be less often necessary to use software arbitrary precision > arithmetic and when you have to it should be a big advantage to be able to > work with words of double size. > > Maybe it would be worth to check whether there are "unfair" tests within the > benchmark like numerics with a precision which can be done in hardware on a > 64-bit processor but needs to be done in software on a 32-bit processor? > This is just another case where just a single number is not enough to > decide whether one or the other computer is faster for what you want to do > with it. So you should probably look into the results for specific parts of > the benchmark if that's possible... > > > Does Mathematica support special instructions like SSE? > > no idea... I'm pretty sure the answer is "yes". It's my understanding that Mathematica now uses the Gnu Multi-Precision Library, which is certainly optimized for P4 and (mostly) for AMD64 (but not for PowerPC). GMP certainly uses SSE. There is plenty of documentation on the GMP website, <http://swox.se/gmp>, as to why 64-bit is so much faster than 32-bit. (Four times faster, at the same clock speeds, in multiplying high-precision floating-point numbers). See, for example, <http://www.swox.se/gmp/32vs64.html> IIRC there's also (floating around SOMEWHERE as a link on this website, but I can't find it right now) a comparison of instruction timings between AMD and P4. Finally, if you use AMD64 you should try the 64-bit patches at <http://www.lix.polytechnique.fr/Labo/Pierrick.Gaudry/mpn_AMD64/> (YMMV--I had some trouble getting them to work). I don't know how to integrate these into Mathematica, either. (Just use the updated libraries in /usr/local, or wherever your GMP installation is?) Finally, the GMP benchmarks are at <http://www.swox.com/gmp/gmpbench.html> comparing processor-by-processor. I, for one, would certainly appreciate comments by WRI technical experts on these issues. --Ron Bruck

**Follow-Ups**:**Re: Re: Comparison of Mathematica on Various Computers***From:*János <janos.lobb@yale.edu>

**References**:**Comparison of Mathematica on Various Computers***From:*karl unterkofler <karl.unterkofler@fhv.at>

**Re: Comparison of Mathematica on Various Computers***From:*"fizzy" <fizzycist@knology.net>