Open MPI User's Mailing List Archives

Subject: Re: [OMPI users] open-mpi behaviour on Fedora, Ubuntu, Debian and CentOS
From: Asad Ali (asad06_at_[hidden])
Date: 2010-04-25 22:27:57

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• Reply: Ashley Pittman: "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 of Fedora and
>> Ubuntu but then it starts giving different results.

> Are you also using the same hardware? Different hardware platforms may
> exhibit different rounding behaviour. After some dependent interations
> such effects might indeed sum up and yield different results. The issue
> is called numeric (in)stability and is not specifically related to
openmpi.

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 results are
same but are wrong and different from those of machine 1.

Cheers,

Asad
"Statistical thinking will one day be as necessary for efficient citizenship
as the ability to read and write." - H.G. Wells

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• Next message: Asad Ali: "Re: [OMPI users] open-mpi behaviour on Fedora, Ubuntu, Debian and CentOS"
• Previous message: Trent Creekmore: "Re: [OMPI users] How to "guess" the incoming data type ?"
• Maybe in reply to: jody: "Re: [OMPI users] open-mpi behaviour on Fedora, Ubuntu, Debian and CentOS"
• Next in thread: Asad Ali: "Re: [OMPI users] open-mpi behaviour on Fedora, Ubuntu, Debian and CentOS"
• Reply: Asad Ali: "Re: [OMPI users] open-mpi behaviour on Fedora, Ubuntu, Debian and CentOS"
• Reply: Ashley Pittman: "Re: [OMPI users] open-mpi behaviour on Fedora, Ubuntu, Debian and CentOS"