OPAL ERROR: Unreachable in file ext3x_client.c at line 112

[JOHN194872]

Hi,
I have this persistent problem when trying to run hello_c in that I get:
OPAL ERROR: Unreachable in file ext3x_client.c at line 112
*** An error occurred in MPI_Init
*** on a NULL communicator
*** MPI_ERRORS_ARE_FATAL (processes in this communicator will now abort,
*** and potentially your MPI job)
[DESKTOP-8HR6ET2:68773] Local abort before MPI_INIT completed completed successfully, but am not able to aggregate error messages, and not able to guarantee that all other processes were killed!
Please help.

I have just loaded openmpi-5.0.9 after try to get around the problem without having to reinstall open mpi but without luck, I originally ran the software using vmware from windows but this suddenly stopped working for some unknow reason.

Many thanks,
John

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Details of the problem

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shell$ mpirun -n 2 ./hello_world

[rhc54]

Really hard to provide any help when you don't give us any of the requested info. What version are you running? How are you executing this "hello" program (singleton, mpirun, other launcher)? Etc.

We give you a template for a reason 🤷‍♂️

[JOHN194872]

Hi, Thanks for your prompt reply. I am running openmpi-5.0.9 and hello_c compiled using make from examples folder (mpicc?). Execution is by ./hello_c. Regards, John

…

________________________________ From: Ralph Castain ***@***.***> Sent: Tuesday, February 10, 2026 6:46 PM To: open-mpi/ompi ***@***.***> Cc: JJR Williams ***@***.***>; Author ***@***.***> Subject: Re: [open-mpi/ompi] OPAL ERROR: Unreachable in file ext3x_client.c at line 112 (Issue #13725) You don't often get email from ***@***.*** Learn why this is important<https://aka.ms/LearnAboutSenderIdentification> [https://outlook.office.com/mail/inbox/id/AAQkAGUxNmZmYTVkLWM3MWEtNGYzMS05ODNkLTc3MjQ1NzcxMWYyOQAQAMNt8CQPmB9GpL%2BUVnRla4M%3D?nativeVersion=1.2026.120.300]rhc54 left a comment (open-mpi/ompi#13725)<#13725 (comment)> Really hard to provide any help when you don't give us any of the requested info. What version are you running? How are you executing this "hello" program (singleton, mpirun, other launcher)? Etc. We give you a template for a reason 🤷‍♂️ — Reply to this email directly, view it on GitHub<#13725 (comment)>, or unsubscribe<https://github.com/notifications/unsubscribe-auth/ATAONVRJKOFBOSBOXFGUOND4LIRR3AVCNFSM6AAAAACUUTGO2WVHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMZTQNZZG44DQNZZGI>. You are receiving this because you authored the thread.Message ID: ***@***.***>

[rhc54]

Looks like it is working fine on OMPI main - I suspect the singletons have been fixed. Might need to try at least the head of the v5.0.x branch, or perhaps the v6.0.x branch - or just use main, if you prefer.

[JOHN194872]

Hi Ralph, I am sorry but I don't understand a word of this. Best regards, John Sent from Outlook for Android<https://aka.ms/AAb9ysg>

…

________________________________ From: Ralph Castain ***@***.***> Sent: Tuesday, February 10, 2026 9:00:11 PM To: open-mpi/ompi ***@***.***> Cc: JJR Williams ***@***.***>; Author ***@***.***> Subject: Re: [open-mpi/ompi] OPAL ERROR: Unreachable in file ext3x_client.c at line 112 (Issue #13725) You don't often get email from ***@***.*** Learn why this is important<https://aka.ms/LearnAboutSenderIdentification> [https://avatars.githubusercontent.com/u/2440928?s=20&v=4]rhc54 left a comment (open-mpi/ompi#13725)<#13725 (comment)> Looks like it is working fine on OMPI main - I suspect the singletons have been fixed. Might need to try at least the head of the v5.0.x branch, or perhaps the v6.0.x branch - or just use main, if you prefer. — Reply to this email directly, view it on GitHub<#13725 (comment)>, or unsubscribe<https://github.com/notifications/unsubscribe-auth/ATAONVRFKWTVFYWMPEUF4HD4LJBFXAVCNFSM6AAAAACUUTGO2WVHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMZTQOBQGY4DANBXHA>. You are receiving this because you authored the thread.Message ID: ***@***.***>

[rhc54]

Not sure I can explain it any further. The OMPI release you are using has a bug - you need to update to a more recent version. They haven't released anything more current just yet, so you're only options are to (a) wait patiently for a release to happen, or (b) use the Git repo.

If that latter one is something you aren't prepared to do, then waiting is your only option 🤷‍♂️

[JOHN194872]

Hi Ralph, thanks again but how can I be sure that the bug is the one which causing my problem? Not even sure what you mean by Git repo. Sent from Outlook for Android<https://aka.ms/AAb9ysg>

…

________________________________ From: Ralph Castain ***@***.***> Sent: Tuesday, February 10, 2026 9:13:25 pm To: open-mpi/ompi ***@***.***> Cc: JJR Williams ***@***.***>; Author ***@***.***> Subject: Re: [open-mpi/ompi] OPAL ERROR: Unreachable in file ext3x_client.c at line 112 (Issue #13725) You don't often get email from ***@***.*** Learn why this is important<https://aka.ms/LearnAboutSenderIdentification> [https://avatars.githubusercontent.com/u/2440928?s=20&v=4]rhc54 left a comment (open-mpi/ompi#13725)<#13725 (comment)> Not sure I can explain it any further. The OMPI release you are using has a bug - you need to update to a more recent version. They haven't released anything more current just yet, so you're only options are to (a) wait patiently for a release to happen, or (b) use the Git repo. If that latter one is something you aren't prepared to do, then waiting is your only option 🤷‍♂️ — Reply to this email directly, view it on GitHub<#13725 (comment)>, or unsubscribe<https://github.com/notifications/unsubscribe-auth/ATAONVRHKU6XCQPJ6IICEQT4LJCW7AVCNFSM6AAAAACUUTGO2WVHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMZTQOBQG42DIMJWGU>. You are receiving this because you authored the thread.Message ID: ***@***.***>

[jsquyres]

Try mpirun -np 1 ./hello_c.

[JOHN194872]

Thanks Jeff but I still get: [DESKTOP-8HR6ET2:70977] OPAL ERROR: Unreachable in file ext3x_client.c at line 112 *** An error occurred in MPI_Init *** on a NULL communicator *** MPI_ERRORS_ARE_FATAL (processes in this communicator will now abort, *** and potentially your MPI job) [DESKTOP-8HR6ET2:70977] Local abort before MPI_INIT completed completed successfully, but am not able to aggregate error messages, and not able to guarantee that all other processes were killed! -------------------------------------------------------------------------- Primary job terminated normally, but 1 process returned a non-zero exit code. Per user-direction, the job has been aborted. -------------------------------------------------------------------------- -------------------------------------------------------------------------- mpirun detected that one or more processes exited with non-zero status, thus causing the job to be terminated. The first process to do so was: Process name: [[16296,1],0] Exit code: 1

…

________________________________ From: Jeff Squyres ***@***.***> Sent: 11 February 2026 2:47 PM To: open-mpi/ompi ***@***.***> Cc: JJR Williams ***@***.***>; Author ***@***.***> Subject: Re: [open-mpi/ompi] OPAL ERROR: Unreachable in file ext3x_client.c at line 112 (Issue #13725) You don't often get email from ***@***.*** Learn why this is important<https://aka.ms/LearnAboutSenderIdentification> [https://avatars.githubusercontent.com/u/617316?s=20&v=4]jsquyres left a comment (open-mpi/ompi#13725)<#13725 (comment)> Try mpirun -np 1 ./hello_c. — Reply to this email directly, view it on GitHub<#13725 (comment)>, or unsubscribe<https://github.com/notifications/unsubscribe-auth/ATAONVQUK2EY34H2A7VTR4L4LM6JBAVCNFSM6AAAAACUUTGO2WVHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMZTQOBUHEYDMMZUGM>. You are receiving this because you authored the thread.Message ID: ***@***.***>

[JOHN194872]

I wonder if the problem is due to old versions of open mpi being accessed which were installed when I used to use vmware? Sent from Outlook for Android<https://aka.ms/AAb9ysg>

…

________________________________ From: JJR Williams ***@***.***> Sent: Wednesday, February 11, 2026 3:51:22 PM To: open-mpi/ompi ***@***.***>; open-mpi/ompi ***@***.***> Cc: Author ***@***.***>; JJR Williams ***@***.***> Subject: Re: [open-mpi/ompi] OPAL ERROR: Unreachable in file ext3x_client.c at line 112 (Issue #13725) Thanks Jeff but I still get: [DESKTOP-8HR6ET2:70977] OPAL ERROR: Unreachable in file ext3x_client.c at line 112 *** An error occurred in MPI_Init *** on a NULL communicator *** MPI_ERRORS_ARE_FATAL (processes in this communicator will now abort, *** and potentially your MPI job) [DESKTOP-8HR6ET2:70977] Local abort before MPI_INIT completed completed successfully, but am not able to aggregate error messages, and not able to guarantee that all other processes were killed! -------------------------------------------------------------------------- Primary job terminated normally, but 1 process returned a non-zero exit code. Per user-direction, the job has been aborted. -------------------------------------------------------------------------- -------------------------------------------------------------------------- mpirun detected that one or more processes exited with non-zero status, thus causing the job to be terminated. The first process to do so was: Process name: [[16296,1],0] Exit code: 1

________________________________ From: Jeff Squyres ***@***.***> Sent: 11 February 2026 2:47 PM To: open-mpi/ompi ***@***.***> Cc: JJR Williams ***@***.***>; Author ***@***.***> Subject: Re: [open-mpi/ompi] OPAL ERROR: Unreachable in file ext3x_client.c at line 112 (Issue #13725) You don't often get email from ***@***.*** Learn why this is important<https://aka.ms/LearnAboutSenderIdentification> [https://avatars.githubusercontent.com/u/617316?s=20&v=4]jsquyres left a comment (open-mpi/ompi#13725)<#13725 (comment)> Try mpirun -np 1 ./hello_c. — Reply to this email directly, view it on GitHub<#13725 (comment)>, or unsubscribe<https://github.com/notifications/unsubscribe-auth/ATAONVQUK2EY34H2A7VTR4L4LM6JBAVCNFSM6AAAAACUUTGO2WVHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMZTQOBUHEYDMMZUGM>. You are receiving this because you authored the thread.Message ID: ***@***.***>

[JOHN194872]

Hi Jeff, do you have any advice on how to progress from my current situation? Many thanks John Sent from Outlook for Android<https://aka.ms/AAb9ysg>

…

________________________________ From: JJR Williams ***@***.***> Sent: Wednesday, February 11, 2026 5:12:56 pm To: open-mpi/ompi ***@***.***>; open-mpi/ompi ***@***.***> Cc: Author ***@***.***>; JJR Williams ***@***.***> Subject: Re: [open-mpi/ompi] OPAL ERROR: Unreachable in file ext3x_client.c at line 112 (Issue #13725) I wonder if the problem is due to old versions of open mpi being accessed which were installed when I used to use vmware? Sent from Outlook for Android<https://aka.ms/AAb9ysg>

________________________________ From: JJR Williams ***@***.***> Sent: Wednesday, February 11, 2026 3:51:22 PM To: open-mpi/ompi ***@***.***>; open-mpi/ompi ***@***.***> Cc: Author ***@***.***>; JJR Williams ***@***.***> Subject: Re: [open-mpi/ompi] OPAL ERROR: Unreachable in file ext3x_client.c at line 112 (Issue #13725) Thanks Jeff but I still get: [DESKTOP-8HR6ET2:70977] OPAL ERROR: Unreachable in file ext3x_client.c at line 112 *** An error occurred in MPI_Init *** on a NULL communicator *** MPI_ERRORS_ARE_FATAL (processes in this communicator will now abort, *** and potentially your MPI job) [DESKTOP-8HR6ET2:70977] Local abort before MPI_INIT completed completed successfully, but am not able to aggregate error messages, and not able to guarantee that all other processes were killed! -------------------------------------------------------------------------- Primary job terminated normally, but 1 process returned a non-zero exit code. Per user-direction, the job has been aborted. -------------------------------------------------------------------------- -------------------------------------------------------------------------- mpirun detected that one or more processes exited with non-zero status, thus causing the job to be terminated. The first process to do so was: Process name: [[16296,1],0] Exit code: 1

________________________________ From: Jeff Squyres ***@***.***> Sent: 11 February 2026 2:47 PM To: open-mpi/ompi ***@***.***> Cc: JJR Williams ***@***.***>; Author ***@***.***> Subject: Re: [open-mpi/ompi] OPAL ERROR: Unreachable in file ext3x_client.c at line 112 (Issue #13725) You don't often get email from ***@***.*** Learn why this is important<https://aka.ms/LearnAboutSenderIdentification> [https://avatars.githubusercontent.com/u/617316?s=20&v=4]jsquyres left a comment (open-mpi/ompi#13725)<#13725 (comment)> Try mpirun -np 1 ./hello_c. — Reply to this email directly, view it on GitHub<#13725 (comment)>, or unsubscribe<https://github.com/notifications/unsubscribe-auth/ATAONVQUK2EY34H2A7VTR4L4LM6JBAVCNFSM6AAAAACUUTGO2WVHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMZTQOBUHEYDMMZUGM>. You are receiving this because you authored the thread.Message ID: ***@***.***>

[rhc54]

It's probably some kind of library confusion - there is no such file as "ext3x_client.c" in OMPI v5.0.9. That only exists in an older version of OMPI v4.x.

[JOHN194872]

Hi Ralph, Thanks for this. I have downloaded and configured v4 . I have also recompiled hello_c.c using make but trying to run it still gives: mpirun -np 1 ./hello_c [DESKTOP-8HR6ET2:127651] OPAL ERROR: Unreachable in file ext3x_client.c at line 112 *** An error occurred in MPI_Init *** on a NULL communicator *** MPI_ERRORS_ARE_FATAL (processes in this communicator will now abort, *** and potentially your MPI job) [DESKTOP-8HR6ET2:127651] Local abort before MPI_INIT completed completed successfully, but am not able to aggregate error messages, and not able to guarantee that all other processes were killed! -------------------------------------------------------------------------- Primary job terminated normally, but 1 process returned a non-zero exit code. Per user-direction, the job has been aborted. -------------------------------------------------------------------------- -------------------------------------------------------------------------- mpirun detected that one or more processes exited with non-zero status, thus causing the job to be terminated. The first process to do so was: Process name: [[55306,1],0] Exit code: 1 Regards, John

…

________________________________ From: Ralph Castain ***@***.***> Sent: 12 February 2026 6:43 PM To: open-mpi/ompi ***@***.***> Cc: JJR Williams ***@***.***>; Author ***@***.***> Subject: Re: [open-mpi/ompi] OPAL ERROR: Unreachable in file ext3x_client.c at line 112 (Issue #13725) You don't often get email from ***@***.*** Learn why this is important<https://aka.ms/LearnAboutSenderIdentification> [https://avatars.githubusercontent.com/u/2440928?s=20&v=4]rhc54 left a comment (open-mpi/ompi#13725)<#13725 (comment)> It's probably some kind of library confusion - there is no such file as "ext3x_client.c" in OMPI v5.0.9. That only exists in an older version of OMPI v4.x. — Reply to this email directly, view it on GitHub<#13725 (comment)>, or unsubscribe<https://github.com/notifications/unsubscribe-auth/ATAONVRKYJ5DG6GYR6KATWD4LTCU5AVCNFSM6AAAAACUUTGO2WVHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMZTQOJSG42DMMRTGM>. You are receiving this because you authored the thread.Message ID: ***@***.***>

[rhc54]

Afraid I have no real ideas - I don't support OMPI v4. You might check that you:

1. really are loading the right libs and using the right mpirun
2. what PMIx version you are loading. OMPI is using the "ext3x" component, so it is using an external PMIx library - which version is it? OMPI v4 doesn't work well with newer versions of PMIx - the one it embeds is v3.2.5
3. you have an available network interface, although "unreachable" should still run as a singleton without reporting an error.

[JOHN194872]

Hi Ralph, thanks for this. I get: mpiexec (OpenRTE) 4.0.3. Please let me know how I can find out about PMIx library. Regards, John

…

________________________________ From: Ralph Castain ***@***.***> Sent: 12 February 2026 10:47 PM To: open-mpi/ompi ***@***.***> Cc: JJR Williams ***@***.***>; Author ***@***.***> Subject: Re: [open-mpi/ompi] OPAL ERROR: Unreachable in file ext3x_client.c at line 112 (Issue #13725) [https://avatars.githubusercontent.com/u/2440928?s=20&v=4]rhc54 left a comment (open-mpi/ompi#13725)<#13725 (comment)> Afraid I have no real ideas - I don't support OMPI v4. You might check that you: 1. really are loading the right libs and using the right mpirun 2. what PMIx version you are loading. OMPI is using the "ext3x" component, so it is using an external PMIx library - which version is it? OMPI v4 doesn't work well with newer versions of PMIx - the one it embeds is v3.2.5 3. you have an available network interface, although "unreachable" should still run as a singleton without reporting an error. — Reply to this email directly, view it on GitHub<#13725 (comment)>, or unsubscribe<https://github.com/notifications/unsubscribe-auth/ATAONVTYZPQ4EAWCGR4TVSD4LT7IRAVCNFSM6AAAAACUUTGO2WVHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMZTQOJTHAYTANBZGE>. You are receiving this because you authored the thread.Message ID: ***@***.***>