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How to Decipher Floating Point Exception

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Old   December 10, 2020, 13:21
Question How to Decipher Floating Point Exception
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Jeffrey Johnston
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Hello,

Heads up, I have no idea what I'm doing .

I am very new to OpenFOAM and CFD in general. I am experimenting with a case which was designed for incompressible flow. I am trying to adapt the case to a compressible flow and solve it using rhoPimpleFoam.

I have been troubleshooting various errors as I go. Most of the errors that I get are clearly described and I can fix them.

However, I have now run into a floating point exception error:

Code:
Starting time loop

Courant Number mean: 0 max: 0
deltaT = 6e-05
Time = 6e-05

PIMPLE: iteration 1
#0  Foam::error::printStack(Foam::Ostream&) at ??:?
#1  Foam::sigFpe::sigHandler(int) at ??:?
#2  ? in /lib/x86_64-linux-gnu/libpthread.so.0
#3  Foam::divide(Foam::Field<double>&, Foam::UList<double> const&, Foam::UList<double> const&) at ??:?
#4  Foam::operator/(Foam::UList<double> const&, Foam::UList<double> const&) at ??:?
#5  Foam::diagonalSolver::solve(Foam::Field<double>&, Foam::Field<double> const&, unsigned char) const at ??:?
#6  Foam::fvMatrix<double>::solveSegregated(Foam::dictionary const&) at ??:?
#7  Foam::fvMatrix<double>::solveSegregatedOrCoupled(Foam::dictionary const&) at ??:?
#8  Foam::fvMesh::solve(Foam::fvMatrix<double>&, Foam::dictionary const&) const at ??:?
#9  ? in ~/OpenFOAM/OpenFOAM-v2006/platforms/linux64GccDPInt32Opt/bin/rhoPimpleFoam
#10  __libc_start_main in /lib/x86_64-linux-gnu/libc.so.6
#11  ? in ~/OpenFOAM/OpenFOAM-v2006/platforms/linux64GccDPInt32Opt/bin/rhoPimpleFoam
Floating point exception (core dumped)
The solver does not seem to even begin solving anything, so I can't see what the numbers were doing. This makes me think my initial and boundary conditions are at fault, but I have checked over them and tried a few different set ups to no avail.

I am not here to get a specific solution to my problem (though that would be nice). Rather, I want to learn how to make sense of these errors. I can't figure out what any of it means. Are these OpenFOAM errors? C++ errors? bash errors?
Where do they come from and where can I find a guide to deciphering not just this problem, but similar errors in future?

Any help appreciated.

Thank you!
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Old   December 11, 2020, 07:47
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Max
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From my experience, I can tell you that such error messages occur when the solver is supposed to perform mathematical operations that are not possible, such as the classic case of division by zero.

Finding the trigger of the problem is often not trivial. In my case, physically meaningless boundary conditions were often the problem. But it could also be the mesh.

I would advise you to check your boundary conditions and your mesh. For the latter, the application checkMesh is highly recommended.
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