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Open MPI-fork() error

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Old   September 2, 2018, 19:37
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I also had the same error after the upgrade of our HPC. Before that the same case ran well. I think it might be a problem of system setting.
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Old   September 21, 2018, 20:01
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Quote:
Originally Posted by smraniaki View Post
I've had the same problem. This is one of those problem drive me crazy! I could unreasonably solve the problem by modifying fvSolution dictionary (changing a smoother). The other time I could get rid of it by changing my decomposition scheme. I still don't know how and why it happens but apparently it comes from ghost cells that are not identifiable by MPI.

Goodluck
Smran
Thank you that was very useful. I know this is a 4 year old post.

But any more insight would be extremely valuable. I have a custom PISO solver with GAMG as matrix solver and with CyclicBC.

Right now I use a GaussSeidel smoother, what smoother did you use to mitigate this problem?

Regards,

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Originally Posted by kkpal View Post
I also had the same error after the upgrade of our HPC. Before that the same case ran well. I think it might be a problem of system setting.
Did you mitigate it?

you have cyclic BCs?

Last edited by wyldckat; September 23, 2018 at 14:38. Reason: merged posts a few minutes apart
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Old   September 21, 2018, 20:31
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Yes. The HPC upgraded the openmpi version. I changed it back to the original version and the problem is solved. I do have cyclic BCs.

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Originally Posted by fedvasu View Post
Did you mitigate it?

you have cyclic BCs?
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Old   September 24, 2018, 17:32
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Originally Posted by kkpal View Post
Yes. The HPC upgraded the openmpi version. I changed it back to the original version and the problem is solved. I do have cyclic BCs.
Thanks kkpal,

But may I know more specific details?

which version of OpenFOAM? did you/admin compile OF with system MPI or OPENMPI from ThirdParty?

which version of OPENMPI gave you this trouble and which(original) version solved it.
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Old   November 30, 2018, 08:00
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That issue still exist with OF 6.0 but you may not have any problem with newer release OF 6.2xx. The problem is basically about the fact that OpenMPI divides CFD case into the processors to solve it simultaneously with different processors and fork() environment might do the same job as an sub-program (let's say) such that it blocks OpenMPI to communicate between processors. It is a bug about OpenMPI and OpenFOAM enviroments
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Old   December 2, 2018, 21:46
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Originally Posted by uckmhnds View Post
That issue still exist with OF 6.0 but you may not have any problem with newer release OF 6.2xx. The problem is basically about the fact that OpenMPI divides CFD case into the processors to solve it simultaneously with different processors and fork() environment might do the same job as an sub-program (let's say) such that it blocks OpenMPI to communicate between processors. It is a bug about OpenMPI and OpenFOAM enviroments
thank youfor letting us know.

is there a specific bug report or reports of this to OF devs?

it is very difficult for me to reproduce, sometimes the simulation crashes/sometimes doesn't if i change my pressure solver from GAMG to PCG it helps and in some other cases it doesn't
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Old   December 4, 2018, 18:12
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Quote:
Originally Posted by fedvasu View Post
thank youfor letting us know.

is there a specific bug report or reports of this to OF devs?

it is very difficult for me to reproduce, sometimes the simulation crashes/sometimes doesn't if i change my pressure solver from GAMG to PCG it helps and in some other cases it doesn't

Actually, i did not report a bug to OF but my institution to upgrade software in clusters. They installed the release OpenFOAM/OpenFoam.org-6.20180918.git, which is still a 6.x version so compatible with older 6.0 version. I would recommend you to do so and you would not need to change anything in your case folders as you had to do between different versions (i.e 2.x to 3.x).
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