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simpleFoam divergence due to hardware/compilation?

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Old   May 16, 2018, 16:17
Default simpleFoam divergence due to hardware/compilation?
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Hi all,


I have a case I am working with using simpleFoam with OpenFOAM 5.0. The problem has a lot of interesting features including variable viscosity and coupled transport equations. I have the same version of OpenFOAM compiled on my Ubuntu 16.04 laptop as well as on the Titan supercomputer at Oak Ridge National Lab. Basically on my laptop, the code seems to execute perfectly with nice convergence, but on Titan, after about 30 seconds of simulation time, simpleFoam suddenly diverges.


I have tried debugging every possible thing I can think of, but when I finally just ran an identical case on two different machines and found divergence on one (after running smoothly for a while), and no divergence on the other machine, I became very concerned. To be honest I do not know enough details about hardware/compilations to debug this problem.


Does anyone have any idea what could be going wrong???


Thanks
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Old   May 17, 2018, 00:29
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Assuming that there is no failure in the large machine, one has to ask What is different? I think that the floating point operating units may be different and with it the internal representation of floating point numbers. A setup at the limits of stability may crashes with some less digits in floating point representation.
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