Re: [OMPI users] open-mpi behaviour on Fedora, Ubuntu, Debian and CentOS

Asad Ali writes: > I took your earlier advice regarding the optimization flags causing errors > in your case. I reiterate that any `errors' are much more likely to be in the code than GCC's -On optimizations if it's unstable with respect to them. > You wrote in reply to Dave > > "The optimizati

Re: [OMPI users] open-mpi behaviour on Fedora, Ubuntu, Debian and CentOS

Hi Gus, Thanks for your well researched and thoughtful reply. It will take a bit of time to absorb such a big and energetic doze. :) I took your earlier advice regarding the optimization flags causing errors in your case. You wrote in reply to Dave "The optimization flags were the main cause of c

Re: [OMPI users] open-mpi behaviour on Fedora, Ubuntu, Debian and CentOS

Fabian Hänsel writes: > You could try to set optimizations more fine-grained. Every > -Osomething stands for a certain set of optimizations. Start with > e.g. "gcc -Q -O2 --help=optimizers" to see all available optimizations > and which are enabled at -O2. Read about them on the gcc > manpage. Di

Re: [OMPI users] open-mpi behaviour on Fedora, Ubuntu, Debian and CentOS

Hello Gus: Thannk you for your excellent and well-considered thoughts on the subject. You educate us all. Douglas. On Wed, Apr 28, 2010 at 02:39:20PM -0400, Gus Correa wrote: > Hi Asad > > I think the speed vs. accuracy tradeoff will always be there. > Getting both at the same time is kind of a

Re: [OMPI users] open-mpi behaviour on Fedora, Ubuntu, Debian and CentOS

Hi Asad I think the speed vs. accuracy tradeoff will always be there. Getting both at the same time is kind of a holy grail, everybody wants it! Whoever asked you to get both gotta be kidding. Somebody already suggested enforcing IEEE floating point standard, if you want numerical accuracy and p

Re: [OMPI users] open-mpi behaviour on Fedora, Ubuntu, Debian and CentOS

On 4/27/2010 11:55 PM, Fabian Hänsel wrote: Hi Ali, I have solved that problem. I just removed the gcc flag -O3 from my compile script and the error vanished. However the speed of my code is also reduced to 50 iterations/minute from 70 iterations/minute, still not bad. Is there any alternat

Re: [OMPI users] open-mpi behaviour on Fedora, Ubuntu, Debian and CentOS

Hi Ali, I have solved that problem. I just removed the gcc flag -O3 from my compile script and the error vanished. However the speed of my code is also reduced to 50 iterations/minute from 70 iterations/minute, still not bad. Is there any alternative to -O3 flag? I tried -O2 too but this al

Re: [OMPI users] open-mpi behaviour on Fedora, Ubuntu, Debian and CentOS

Hi all, Many many thanks to all of you for your time, sincere help, useful tips and advices. I have solved that problem. I just removed the gcc flag -O3 from my compile script and the error vanished. However the speed of my code is also reduced to 50 iterations/minute from 70 iterations/minute, st

Re: [OMPI users] open-mpi behaviour on Fedora, Ubuntu, Debian and CentOS

Hi Dave Dave Love wrote: Gus Correa writes: Or run a serial version on the same set of machines, compiled in similar ways (compiler version, opt flags, etc) to the parallel versions, and compare results. If the results don't differ, then you can start blaming MPI. That wouldn't show that th

Re: [OMPI users] open-mpi behaviour on Fedora, Ubuntu, Debian and CentOS

Gus Correa writes: > Or run a serial version on the same set of machines, > compiled in similar ways (compiler version, opt flags, etc) > to the parallel versions, and compare results. > If the results don't differ, then you can start blaming MPI. That wouldn't show that there's actually any Ope

Re: [OMPI users] open-mpi behaviour on Fedora, Ubuntu, Debian and CentOS

On Apr 26, 2010, at 12:03 PM, Dave Love wrote: > Sorry, but that's naïve, even if you can prove your code is well-defined > according to the language and floating-point standards. You should > listen to Ashley, and if it worries you, you really need just to debug > it. If you believe it's a prob

Re: [OMPI users] open-mpi behaviour on Fedora, Ubuntu, Debian and CentOS

Dave Love wrote: Asad Ali writes: >From run to run the results can only be different if you either use different input/output or use different random number seeds. Here in my case the random number seeds are the same as well. Sorry, but that's naïve, even if you can prove your code is well-d

Re: [OMPI users] open-mpi behaviour on Fedora, Ubuntu, Debian and CentOS

Asad Ali writes: >>From run to run the results can only be different if you either use > different input/output or use different random number seeds. Here in my case > the random number seeds are the same as well. Sorry, but that's naïve, even if you can prove your code is well-defined according

Re: [OMPI users] open-mpi behaviour on Fedora, Ubuntu, Debian and CentOS

Sylvestre Ledru writes: > This code will set the precision to double: > > #include > fpu_control_t _cw; > _FPU_GETCW(_cw); > _cw = (_cw & ~_FPU_DOUBLE) | _FPU_EXTENDED; > _FPU_SETCW(_cw); > > You should get the same result on 32 & 64 bits CPU then. Quite off-topic, but as far as I remember f

Re: [OMPI users] open-mpi behaviour on Fedora, Ubuntu, Debian and CentOS

On 4/26/2010 2:31 AM, Asad Ali wrote: On Mon, Apr 26, 2010 at 8:01 PM, Ashley Pittman > wrote: On 25 Apr 2010, at 22:27, Asad Ali wrote: > Yes I use different machines such as > > machine 1 uses AMD Opterons. (Fedora) > > machine 2 and 3

Re: [OMPI users] open-mpi behaviour on Fedora, Ubuntu, Debian and CentOS

On Mon, Apr 26, 2010 at 8:01 PM, Ashley Pittman wrote: > > On 25 Apr 2010, at 22:27, Asad Ali wrote: > > > Yes I use different machines such as > > > > machine 1 uses AMD Opterons. (Fedora) > > > > machine 2 and 3 use Intel Xeons. (CentOS) > > > > machine 4 uses slightly older Intel Xeons. (Debian

Re: [OMPI users] open-mpi behaviour on Fedora, Ubuntu, Debian and CentOS

, Jim Conboy ( Culham Ctr for Fusion Energy ) -Original Message- From: users-boun...@open-mpi.org [mailto:users-boun...@open-mpi.org] On Behalf Of Ashley Pittman Sent: 26 April 2010 09:02 To: Open MPI Users Subject: Re: [OMPI users] open-mpi behaviour on Fedora, Ubuntu,Debian and

Re: [OMPI users] open-mpi behaviour on Fedora, Ubuntu, Debian and CentOS

On 25 Apr 2010, at 22:27, Asad Ali wrote: > Yes I use different machines such as > > machine 1 uses AMD Opterons. (Fedora) > > machine 2 and 3 use Intel Xeons. (CentOS) > > machine 4 uses slightly older Intel Xeons. (Debian) > > Only machine 1 gives correct results. While CentOS and Debian

Re: [OMPI users] open-mpi behaviour on Fedora, Ubuntu, Debian and CentOS

Hello, Le lundi 26 avril 2010 à 14:33 +1200, Asad Ali a écrit : > Hi Jodi, > > > I once got different results when running on a 64-Bit platform > instead of > > a 32 bit platform - if i remember correctly, the reason was that on > the > > 32-bit platform 80bit extended precision floats were use

Re: [OMPI users] open-mpi behaviour on Fedora, Ubuntu, Debian and CentOS

Hi Asad I must admit i don't know how one can find out whether extended precision is being used or not. I think one has to read up on the CPU's information. I only know that most Intel 32bit-Processors use the extended precision http://en.wikipedia.org/wiki/X86 as does AMD Athlon http://www.a

Re: [OMPI users] open-mpi behaviour on Fedora, Ubuntu, Debian and CentOS

Hi Jodi, > I once got different results when running on a 64-Bit platform instead of > a 32 bit platform - if i remember correctly, the reason was that on the > 32-bit platform 80bit extended precision floats were used but on the 64bit > platform only 64bit floats. Could you please give me an id

Re: [OMPI users] open-mpi behaviour on Fedora, Ubuntu, Debian and CentOS

Hi Fabian, Hi Asad, >> I >> found that running the same source code on these OS, with the same >> versions of of gcc and open-mpi installed on them, gives different >> results than Fedora and Ubuntu after a few hundred iterations. The first >> few hundered iterations are exactly similar to that o

Re: [OMPI users] open-mpi behaviour on Fedora, Ubuntu, Debian and CentOS

I once got different results when running on a 64-Bit platform instead of a 32 bit platform - if i remember correctly, the reason was that on the 32-bit platform 80bit extended precision floats were used but on the 64bit platform only 64bit floats. On Sun, Apr 25, 2010 at 3:39 AM, Fabian Hänsel

Re: [OMPI users] open-mpi behaviour on Fedora, Ubuntu, Debian and CentOS

Hi Asad, I found that running the same source code on these OS, with the same versions of of gcc and open-mpi installed on them, gives different results than Fedora and Ubuntu after a few hundred iterations. The first few hundered iterations are exactly similar to that of Fedora and Ubuntu

[OMPI users] open-mpi behaviour on Fedora, Ubuntu, Debian and CentOS

Hi All, I had been using open-mpi for parallel computing on Fedora and Ubuntu and everything was going quite fine. But recently I started using other OSs such as CentOS and Debian and found a strange thing regarding mpi. I found that running the same source code on these OS, with the same versions