# Using two machines with different preCICE version

**URL:** <https://precice.discourse.group/t/using-two-machines-with-different-precice-version/2190>\
**Category:** Using preCICE\
**Created:** [October 28, 2024, 3:46pm UTC](https://precice.discourse.group/t/using-two-machines-with-different-precice-version/2190 "2024-10-28T15:46:04Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![JulianK](https://avatars.discourse-cdn.com/v4/letter/j/779978/32.png) [@JulianK](https://precice.discourse.group/u/JulianK)\
**Post date:** [October 28, 2024, 3:46pm UTC](https://precice.discourse.group/t/using-two-machines-with-different-precice-version/2190/1 "2024-10-28T15:46:04Z")

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Hi everyone,  
we are trying to couple CFD and FEM.  
Setting up the coupling works, if both programs are installed on the CFD cluster.

Now we want to couple two different clusters in the same subnet:  
CFD: CentOS 7.4.1708 (Core)  
FEM: Red Hat Enterprise Linux release 8.5 (Ootpa)

We have preCICE 2.3.0 installed on the CFD cluster and preCICE 2.5.0 on the FEM cluster.  
The participants are not able to find each other, but neither of the participants shows an error message. Both are showing something like:  
“—[precice] Setting up master communication to coupling partner/s”

The precice-run folder is created and the IP is as intended.

Is it possible that the participants can not find each other because of the version difference between the two clusters?

Thank you in advance for your help.

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**Author:** ![uekerman](https://yyz2.discourse-cdn.com/free1/user_avatar/precice.discourse.group/uekerman/32/2199_2.png) [@uekerman](https://precice.discourse.group/u/uekerman)\
**Post date:** [November 7, 2024, 3:36pm UTC](https://precice.discourse.group/t/using-two-machines-with-different-precice-version/2190/2 "2024-11-07T15:36:36Z")

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Hi @JulianK,

In general, mixing preCICE versions is strongly discouraged. As soon as there are changes in the underlying communication layer, anything can happen.

Properly checking this is actually sth we have on our roadmap since longer:

> <https://github.com/precice/precice/issues/669>
>
> \# Problem Description
> 
> When running a simulation with multiple participants, t…here is always the possibility that they may link to differing versions.
> 
> Currently, this will run, could work and may crash.
> 
> \# Suggested Solution
> 
> Exchange version information directly after establishing each master connection.
> Then assert that the remote version matches the local version.

Between v2.3 and v2.5, there were changes in the communication. Hard to say whether they could cause the behavior you describe. There could also be other reasons obviously:

> [@Help! The participants are not finding each other!](https://precice.discourse.group/t/help-the-participants-are-not-finding-each-other/646):
>
> A possible situation, without an error: one or both/multiple participants display the message Setting up master communication to coupling partner/s and nothing happens, even though this step should complete instantaneously.

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**Author:** ![system](https://global.discourse-cdn.com/free1/uploads/precice/original/1X/67d2a5fa6f80e597e2267ff17fa8c1673cd11caa.svg) [@system](https://precice.discourse.group/u/system)\
**Post date:** [March 19, 2025, 3:20pm UTC](https://precice.discourse.group/t/using-two-machines-with-different-precice-version/2190/3 "2025-03-19T15:20:27Z")

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Closed on March 19, 2025, 3:20pm UTC

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