Speeds of different versions of OpenFOAM
 

Hi, just a simple question:

Is there any difference for the speeds of OF1.5, OF1.6 and OF1.7? I mean the times used for some basic solvers such as icoFoam with same mesh, same parameters, same computer,,,,

Thanks.

Hi ywang,

Well, you also have to take into account the Gcc version used to compile them! Let me see if I remember this right:

• OpenFOAM 1.5 and 1.6 can only be compiled with gcc 4.3.x;
• OpenFOAM 1.6.x can be compiled with gcc 4.3.x and 4.4.x;
• OpenFOAM 1.7.x can be compiled with gcc 4.3.x, 4.4.x and 4.5.x.

Now, Gcc 4.4.x creates better perfoming binaries than 4.3.x; and then Gcc 4.5.x surpasses even Intel's C Compiler (Icc)!

Therefore one would have to compare runtimes with every OpenFOAM version built with Gcc 4.3.x. But yes, I expect improved performance between versions, since there are some slight tunings made from version to version. But I don't have any hard data with these results for proof.

Best regards,
Bruno

Thanks, Bruno.

Yes, I know different OF version built with different gcc,,, The background of my question is that I am using OF1.5 with gcc4.3.2 on a suppercomputer and OF1.7 with gcc4.4.4 on my workstation, and I find the speed for one processor in the suppercomputer is slower than the one in my workstation.

The latest gcc in the suppercomputer is gcc4.3.2.....I have tried to build gcc4.4.4 and OF1.7 on it but failed due to something about cross-compiling wrong. ... I think I should try again.

The CPU on your supercomputer might be slower than your workstation CPU. The "super" comes from the amount of processors, not the speed of a single one.

From another thread it looks like the supercomputer you are talking about is bluegene. From what I can find on the net bluegene's CPUs run at 700 MHz and a fairly small cache, giving it 2.8 GFLOPS processing power. For comparison, an Intel i7 can reach up to 109 GFLOPS!

Yes, it's bluegene/p and I have considered the difference of CPUs. I mean it's slower than I expected(considered the difference of hardware). I will try to build OF with different compilers.

Hi Bruno,

Do you know how to build OpenFOAM with the IBM XL compilers? I had a try and got many many errors.

Yong

Hi Yong,

Sadly I don't have any experience with it :(

But you can try contacting Matteo Lombardi, from the other thread: http://www.cfd-online.com/Forums/ope...-bluegene.html

This might also give you some hints:

• https://ccni.rpi.edu/wiki/index.php/OpenFOAM
• https://ccni.rpi.edu/wiki/images/6/6...stallGuide.pdf

Nonetheless, what I usually suggest is running Allwmake like this:Then use a text editor to replace any sensitive data, such as folder paths and user names. Then compress the modified log
and attach it to your next post! I like a good challenge, specially with new compilers and architectures :D Although getting my hands on the machine would be the best, but when not possible, there's always error logs :D

Best regards,
Bruno

Hi Bruno,

Thanks.

1- I was communicating with Matteo and got help from him when I was building OF1.5.x with Gcc4.3.2 on BG/P. What impressed me most from him was the word "nightmare". lol... Anyway, he gave up building OF with XL compiliers.

2- I have noticed CCNI and found they were using static libraries. Matteo and I are using dynamic libraries.

3- I found there are several places/groups using OF on BG/P (CCNI, Matteo's group, KAUST at http://www.hpc.kaust.edu.sa/document...e_environment/, and so on), but all are with Gcc at present. ...I believe it will be a challenge building OF with XL. Anyway, let's have a try. :)

Yong