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Re: [lammps-users] Computer Difference
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Re: [lammps-users] Computer Difference


From: Wes Barnett <w.barnett@...668...>
Date: Thu, 14 Sep 2017 08:33:21 -0400



On Thu, Sep 14, 2017 at 7:49 AM, Emir Koçer <emirkocer92@...92......> wrote:

Hello again,
-on Windows 7 Enterprise we have lmp_mpi dated to 15 May 15, on Linux Debian we have lmp_mpi dated to the latest version (11 Aug 17)


There's a two year difference in those versions. Have you checked the change log to see if a bug related to these calculations has been fixed, changed have been made to the algorithm, etc?
 

- calculating thermal conductivity of pure water with TIP5P rigid model
- on Windows we get 0.63 W/mK with a std of 0.02-0.03, on Linux we get 0.85 W/mK with a std of 0.02-0.03 (experimental value is 0.60 W/mK )

It's hard to compare Windows vs. Linux if you are running two different versions of LAMMPS.
 

- sampling time is 20 ps and yes we can rule out them.
with another water models (TIP3P,etc.) which are not rigid, I get almost same results from both machines, so I've started to believe that there may be something different about the rigid algorithm of GK in two systems, but this is just my guess after checking everything.

TIP3P most certainly is a rigid water model unless you are specifying it not to be.
 



On 14-09-2017 14:35, Giacomo Fiorin wrote:
You need to copy the list on reply.  

On Sep 14, 2017 7:27 AM, "Emir Koçer" <emirkocer92@...24...> wrote:

Hello again,
-on Windows 7 Enterprise we have lmp_mpi dated to 15 May 15, on Linux Debian we have lmp_mpi dated to the latest version (11 Aug 17)
- calculating thermal conductivity of pure water with TIP5P rigid model
- on Windows we get 0.63 W/mK with a std of 0.02-0.03, on Linux we get 0.85 W/mK with a std of 0.02-0.03 (experimental value is 0.60 W/mK )
- sampling time is 20 ps and yes we can rule out them.
with another water models (TIP3P,etc.) which are not rigid, I get almost same results from both machines, so I've started to believe that there may be something different about the rigid algorithm of GK in two systems, but this is just my guess after checking everything.

Emir


On 12-09-2017 23:27, Giacomo Fiorin wrote:
You should provide some information:
- what are the exact versions of the Windows and Linux executables, and who compiled them?
- what are the dynamic properties you are computing with the Green-Kubo formalism?
- what are their computed values?
- what is the sampling time?
- can you safely rule out sampling errors?



On Tue, Sep 12, 2017 at 12:41 PM, Emir Koçer <emirkocer92@...1125.....> wrote:
Dear all,
I ran exactly same scripts on different machines (windows and linux).  Windows has one of the 2016 versions of LAMMPS and Linux has the latest version. Simulations are TIP5P pure water models with Green-Kubo algorithm (EMD). They have similar results when I run TIP3P models, but with TIP5P, Linux machine overestimates the experimental result, while Windows' results are in good agreement with the experiment. Both machines are operating properly and have no observable problems (We use them a lot in our research and this is the only type of simulation they disagree with each other).
Can somebody explain this situation ?

Emir


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Giacomo Fiorin
Associate Professor of Research, Temple University, Philadelphia, PA
Contractor, National Institutes of Health, Bethesda, MD




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James "Wes" Barnett
Postdoctoral Research Scientist
Department of Chemical Engineering