[CLUE-Tech] Re: ugly math crunching

[jim feldman]

Unless you can decompose your "ugly" math problem to multiple threads, I 
don't know that MP (or even HT'ing) is going to help much.  You're 
mostly looking for good FPU performance and big on-chip caches which 
either the Opteron or Xeon's should get you.  If you go for the Intel 
solution, spring for their C or fortran compiler.   You should also 
check out Portland Group's optimized compiler and libraries.  And, yes, 
it is "rocket science".  A lot of  DEC's alpha number crunching prowess 
came from the compiler backend.  That group went to Intel during the 
breakup, and they know some mighty good tricks to keep pipelines filled, 
and branches predicted.

If you can decompose your calculations, make sure you build your kernel 
with the correct chip optimizations as well as your C compiler and 
libraries to get all the benefit

Of the tests I've seen (for instance 
http://www.anandtech.com/linux/showdoc.aspx?i=2163), the Xeon's did 
better in pure FLOPS, but in nearly everything else, the opteron's 
either matched or kicked some serious Intel tail, and you can pick up a 
dual opteron MB and 2 of the 25x chips for under $2k( a 4x850+MB will be 
closer to $8k).  Needless to say, pick a MB that gives you the fastest 
memory options, and you may want to create ram disk for your data.

There are some groups who've taken the GPU's in high end graphics cards, 
and turned them into screaming number crunchers too.

Windoze isn't even discussed in polite HPTC circles

>From: "Dale K. Hawkins" <dhawkins at cdrgts.com>
>
>We need a computer to handle some pretty hairy calculations.  We have
>run some tests and estimates and believe our current 1 GHz box will take
>nearly a week to finish the calculations.  And then we will want to make
>some modifications and re-run the calculations.  So, I need a speed
>daemon; a computer capable opening a can of whup-ass on some ugly math
>problems.
>
>So I narrowed my decision to either a the P4 HT series or maybe a dual
>Opteron system.
>
>I plan to run Debian (64-bit for the Opterons).
>
>We have a computer guy with some suggestions, but his opinion of the
>64bit systems is based on dealings with microsoft, vs. a natively
>compiled OS.
>
>Anyhow, I'd appreciate any feedback.
>
>-Dale
>