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-   -   Should I use HPC on SMP PC (http://www.cfd-online.com/Forums/cd-adapco/53426-should-i-use-hpc-smp-pc.html)

tomosada August 6, 2003 22:18

Should I use HPC on SMP PC
 
Should I use HPC on SMP PC ?

I used prostar and starlink to run my case, but the slover program only use half cpu resource .

So, it become more slow than only one cpu PC .

So, Should I use HPC on SMP PC ?

tomosada

Michiel August 7, 2003 07:16

Re: Should I use HPC on SMP PC
 
HI Tomosada,

SMP PC's have only one cable connecting the CPU's and the memory. If one of the CPU's needs data from the memory it occupies the cable. The other CPU has to wait until this action is completed. This is probably the case in your problem. When we were building a linux cluster, it was advised to use single CPU machines for that reason. In this case each CPU has its own memory and only the boundaries between the computational domains have to be exchanged over a network.

In general, if you have small problems that stay within the cache of your CPU with little data transfer to the memory en even worse disk, SMP machines might speed up your problem a lot otherwise need to rethink your computational strategy.

Good luck Michiel

Joern Beilke August 7, 2003 07:36

Re: Should I use HPC on SMP PC
 
It is not that worse in practice. Usually you can get a speedup of about 1.6 on an SMP PC. Sometimes more and sometimes less.

4xF August 7, 2003 13:01

Re: Should I use HPC on SMP PC
 
I have personnaly performed measurements on my SMP machine (DELL server) running a case with 100,000 in serial on one processor, then in parallel with 2 nodes on the twin processor, and at last with two nodes, one of the twin-processor and one on another PC linked via 100Mbs Ethernet. The speed up when using two nodes on the twin processor was 1.4, when using two nodes communicating over Ethernet 2.1 (superlinearity).

Mikhail August 29, 2003 10:49

Re: Should I use HPC on SMP PC
 
Hi Michiel, I think you are mistaken about cable occupying. Try to start 2 StarCD(single threaded) runs on dual PC machine and you will find that they don't influence on each other. Best regards, Mikhail


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