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Albert February 17, 2003 10:52

Linux ???

I would like to know if there are real advantages using linux system.

Thank you Albert

cjtune February 17, 2003 13:16

GNU/Linux advocates! Converge!
Lowest cost of ownership? (No.1 reason) UNIX systems cost a bomb and Windows licenses are per CPU. Linux is per USER and are mostly free or near-free. Licensing is also flexible also, allowing you to make modifications to the OS if you want/need to (open source). UNIX hardware also tend to be very proprietry and you can only get (often expensive) replacement/upgrade parts and support from the UNIX system maker itself. Linux can run on more commonly available and affordable hardware, and everybody knows that this was how MS-DOS (and later Windows) became so ubiquitous.

Stability? UNIX/Linux is generally regarded as more robust than Windows. But, if the software you use is already buggy and poorly-programmed, then I suppose there's no difference. But all of this is my own in-grained experience and observation so no need to start a flame war here...

Performance? I did some benchmarks in my idle time and found out that even with the bloated XFree86 X-server and KDE/Gnome windows managers running, Linux edged out Windows in solving for a STAR-CD cases about 5% faster. Both Linux and Windows (2000, workstation) were on the same machine.

STAR-CD. If I'm not mistaken, the Windows version cannot handle moving meshes for parallel runs. The rest should be the same. Oh, btw, some packages like those from the ES series (ES-ICE, ES-Aero, ES-Uhood, etc.) aren't available for Windows (yet?) but you get them for Linux.

Last I counted, 99% of HPC clusters and about 50% of web servers run on Linux.

kevin February 18, 2003 01:30

Re: GNU/Linux advocates! Converge!
hmm, es-aero and es-uhood are available for windows, but es-ice is not

Andreas February 18, 2003 06:25

Re: GNU/Linux advocates! Converge!

we started to use StarCD in Windows. But unfortunately we had some problems where the support couldn't help us because they seem to have less experience with windows systems than with linux. Well, we decided to work with Linux, contacted the support and received the linux version. But guess what!? You have to buy the Absoft Compiler extra if you want to run Star with Linux. Without starlink wouldn't work. That makes 699 bucks more! But hey, the StarCD licenses are really cheap ... ;-)

greets, Andi

cjtune February 18, 2003 11:03

Re: GNU/Linux advocates! Converge!
Oh yeah. Some of the ES-series stuff are available to Windows. Probably takes time to port. As for Linux, I really wish that CD-Adapco will in the future, give customers the option of using g77 instead of Absoft ProFortran (but g77's performance really sucks compared to Absoft's f77). Perhaps they have their reasons, and I guess it's probably because of the terms of being 'open source'. I think most open-source licenses state that if your code is derived from those of a open-source code (say, g77 run-time libraries), it must be open-source too -something like that. Anyhow, for all UNIX versions of STAR-CD, fortran is *mandatory* and will have to be purchased separately because each UNIX is different from each other and your fortran compiler too must be suited for your particular flavour of UNIX.

But for the best of both worlds (Windows for ease-of-use and Linux for all the other reasons I've stated), just make your system dual-boot. Make sure you have an intermediate FAT32 partition (sort of a 'demilitarized zone') if you want to export data from your Linux STAR-CD because windows can't see Linux partitions. Normally most Linux distros can recognize and automount NTFS (Windows) partitions but don't count on it (RedHat 8 doesn't).

Andreas February 18, 2003 11:55

Re: GNU/Linux advocates! Converge!
Hmm. I switched to Linux because the support doesn't run Star with windows. I had some errors they never heared about. In my opinion is Adapcos sales policy wrong. If I by a program for my system it has to work without purchasing another program.

Vladimir Krejci February 18, 2003 13:08

Re: GNU/Linux advocates! Converge!
You have to buy Absoft Fortran Compiler for MS Windows too.

Andreas February 18, 2003 14:14

Re: GNU/Linux advocates! Converge!
Right, but only to compile user subroutines.

Albert February 19, 2003 08:33

Re: GNU/Linux advocates! Converge!

I agree with you. One year ago, for example, VOF worked badly on windows e y+ calculation was wrong.

But what about calculation speed?


cjtune February 19, 2003 10:54

Re: GNU/Linux advocates! Converge!
Most common was the dreaded 'Segmentation Fault'... but I seem to see much less of it in v3.150A for Windows.

dakost February 20, 2003 18:44

Re: GNU/Linux advocates! Converge!
Linux offers great performance / value, but has anyone here managed to get a Star-CD executable over 2Gb to run on Linux? As far as i know this is a limit for 4Gb based Linux workstations. Maybe the new Intel 7505 workstations which can support up to 12 Gb of memory and the cpu - memory interface is 36bit can go over the 2 Gb limit? Does anyone have any experience with a 7505 machine?

CJ Tune February 20, 2003 21:55

Re: GNU/Linux advocates! Converge!
Pentium Xeons can address up to 16GB. If you can get Itanium chips (they have versions of Linux for the IA-64) then you can address (theoretically; up to the motherboard to implement it) up to 512GB. But once you need more than 4GB to solve a case, I think it's time to consider clustering, which is Linux's strong point.

Maybe you can't save files in Linux that are more than 2GB big because it is the limitation of the filesystem you are using. Newer, journaling filesystems like JFS, XFS, and ReiserFS should not have that 2GB limit (which I think may be a limitation of the ext2 and ext3 FS). UNIX experiences this issue too. My overnight sim yesterday mysteriously stopped, and when I checked, the .pstt file was (coincidentally?) 2GB. Can't remember what kind of filesystem on my HP machine.

tomk February 21, 2003 19:51

Re: GNU/Linux advocates! Converge!
I am using six 2.0GHz Xeon LINUX machines with 2 gig of memory on each. We use Redhat LINUX 7.3. I can write transient output files greater than 2 GB, but can't get prostar to open them. I have been told that it is a limitation with the LINUX version of star-cd. Does anyone know a way to break these files up outside star? There is a utility inside star, but you have to be able to open the file first. Thanks...

cjtune February 22, 2003 00:54

Re: GNU/Linux advocates! Converge!
I tried opening a 3GB .pstt file with ProSTAR. The reason ProSTAR fails to open it is that it isn't even in the file selection list at all! (ProSTAR somehow can't see it)

I have to ask two things: 1.) Is there a way to save .pstt files in segments during a run? (something like periodic saves of .pst files). 2.) How do I recover my results and not do a rerun from start (assuming question 1 has a favourable answer).

At least your Linux filesystem permits the writing of files bigger than 2GB. My HP-UX 10.2 VxF filesystem simply complains 'file too big' and will halt all operations to append to the .pstt file.

Can anybody confirm that UNIX STAR-CD does not have this bug?

dakost February 22, 2003 15:37

Re: GNU/Linux advocates! Converge!
I had heard elsewhere that the 2Gb limit may not be a Star-Cd issue, but an os or filesystem issue.

It would be interesting to see if anyone not using ext2 or ext3 but using xfs or jfs or reiserfs still has the 2Gb problem limit! Anyone?

cjtune February 23, 2003 11:30

Re: GNU/Linux advocates! Converge!
I use XFS. No problem reading my 3GB post file (I can 'tail' it to get a dump of binary stuff) through the shell but not through ProSTAR (ProSTAR can't see it). Ext2 had some filesystem limits but I'm not sure it's a maximum inode issue or maximum file size issue. Ext3 is just a 'upgraded' version of ext2 with journalling bolted-on and does inherit those limitations.

Gzip'ed it up and ftp'ed to my HP UNIX machine for post-processing (to see whether the true-blue UNIX STAR-CD has that problem too or not) but in the middle of gunzip'ing, HP-UX 10.20 complains 'file too big' and aborts the decompression process. This machine uses VxF (journalling).

dakost February 23, 2003 17:39

Re: GNU/Linux advocates! Converge!
There is no problem with loading pst or pstt files or merging them (from a hpc run) or running bigger executables then 2Gb on HPUX 11.0 based machines as long as the system has enough physical memory, swapsize and the kernel is tweaked to allow for big data and test files (there are 2 entries for the limit of 32 bit data and text files sizes and 2 entries for 64 bit data and file sizes in the HPUX kernel). We run 5.9 million cell cases on linux machines in hpc and then have to do the merging on HP machines. I shall have to try and see how a non ext2 or ext3 filesystem fares.

CJ Tune February 23, 2003 21:09

Re: GNU/Linux advocates! Converge!
Well, it's probably a linux-only (ProSTAR) problem but I have no way of verifying it at the moment -Linux's filesystems are able to handle large, >2GB files. My windows partitions don't enough space and my HP-UX 10.20 machine definitely can't create files bigger than 2063835136 bytes (max tweakable in kernel). Let's see what's the feedback from CD-Adapco about this.

kevin February 25, 2003 14:18

Re: GNU/Linux advocates! Converge!
the new 521 prostar version supports >2GB files on linux

CJ Tune February 25, 2003 20:45

Re: GNU/Linux advocates! Converge!
Is it out yet or is it still in development?

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