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Seb January 29, 2004 10:53

Performance of fluent on win200 and linux
Hi all,

We are using fluent 6.1 on dual win2000 workstations with 4gb of memory and 3ghz dual P4. In order to break the 2gb memory barrier per process on win2k, we are thinking on migrating to linux. The problem is that our personal does not support linux and I must bring several good arguments on the advantages of linux over win2000 (besides breaking the 2gb barrier).

I would like to know if fluent runs faster in parallel on linux (links to reliable info would be appreciated) and if there are any big disavantages on running fluent on linux.

Thanks in advance.

Robert Hart January 29, 2004 13:21

Re: Performance of fluent on win200 and linux
Why don't you ask them for a list of reasons why you should stick with windows?

I would be surprised if you could measure a performance difference large enough to persuade hostile personal that it is worth the effort.

Having said that, I run fluent on Linux everyday, and can not think of a single disadvantage.


1) A standard linux kernel will only give you 3Gb per process (although I think there are patches out there which would give you pretty much the full 4gb).

2) Cost - linux is free. You also wont need to shell out for a C compiler if you want to use UDFs.

3) Hardware support - if you are talking about installing linux on your current workstations (I assume you are). You may need to check that your hardware is properly supported. I had problems for a while with my NVidia graphics card, but it seems ok now.

4) Stability & Reliability. My linux box has *never* crashed, and regularly runs for 6 months or longer without a reboot. (I only reboot to install new kernels) Likewise with filesystems, most linux installations will let you use a journalled file system, which are very resistant to losing your data.

5) Better support for batch processing & background execution. Dunno if you do this, but this is a Unix strong point.

6) Portability of data. You will have to be slightly careful about moving data from one operating system to the other. There are a few gotchas (particularly if you use UDFs) but nothing major.

My advise would be to wait until nobody's looking and install linux, get to know it, etc. After six months you wont look back.


Seb January 29, 2004 14:00

Re: Performance of fluent on win200 and linux
Thanks Rob,

I work for a large corporation and changing things are not that easy. Must of our communications and exchange of information goes through lotus notes and everything is based on windows, even CFD. For normal day to day tasks I have nothing to complain about. But or CFD, I think it would ease my job to work with linux. It better handles cpu intensive jobs and allows working with larger (there is not 2gb barrier). I know linux pretty well (better than win2k...) and I might be able to get it on my workstation if needed.

1) Thanks for the info about the standard linux kernel. But I do not know it it still the case, I heard this limitation is no longer an issue (but i am not sure).

2) Cost is not an issue.


Rob Hart January 29, 2004 14:29

Re: Performance of fluent on win200 and linux
On the 3Gb issue, see for example:


To the best of my knowledge these patches haven't been included in the stock kernel as of 2.6.1, so are unlikely to make it into mainstream for some time.

That doesn't mean there aren't distributions that use them, and as you sound pretty confident with linux, you wont be too worried about rolling your own kernel.


Seb January 29, 2004 14:37

Re: Performance of fluent on win200 and linux
Thanks Rob,

for the 3gb issue. There is a workaround with red hat enterprise es3 :

look for : as the hugemem kernel . This kernel supports a 4GB per process user space (versus 3GB for the other kernels), and a 4GB direct kernel space. Using this kernel allows Red Hat Enterprise Linux to run on systems with up to 64GB of main memory.

But the best for me would be to convince my boss to buy an Itanium2 workstation. with a 64 bit architecture the memory limitations are pushed a lot further...

ap January 29, 2004 20:51

Re: Performance of fluent on win200 and linux
I agree with Robert Hart, linux is a lot more stable and reliable than Windows. You need less manteinance and you can forget crashes and silly error messages.

Hi :)


Rob Hart January 30, 2004 05:49

Re: Performance of fluent on win200 and linux
Not sure about the silly error messages - he still wants to run fluent after all. ;-)



easycad February 5, 2004 16:08

Re: Performance of fluent on win200 and linux
Hi! Why dont you check for benchmarking info? Whoops they have updated the info and there are no more benchmarks on windows, only linux and etc. But i think you can request older info. For example for simulation using DPM linux was faster by 50%(!).

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