Exclusivity Issue Running Fluent Using Linux HPC Resources

comiskeyp · April 10, 2025, 09:48

Hi Everyone,

My goal is to run Fluent from a Windows workstation using Linux HPC resources and following these instructions, I'm successfully able to do this when I use the Fluent launcher. However, Fluent by default runs exclusively on a node which creates an issue when another HPC user is using only a few CPUs on that node. It results in a very long queue time (our scheduler is Slurm) because Fluent will simply not spawn on the remaining CPUs of that node until the other user is done.

As a result, I've been looking for a remedy and came across an undocumented command on an Ansys help forum, "-scheduler_exclusive=0", which turns off this default exclusive behavior. The problem I'm having with this is that in order to use the command, I have to launch Fluent with the Windows Command Prompt and I'm receiving an error which I do not get when using the Fluent launcher.

When trying to open Fluent (with or without the scheduler, MPI, or interconnect - I get the same result) via the Command Prompt typing:

Code:

fluent 3ddp -meshing -t8 -cnf=<HOST FILE>

I get the following error:
ErrorScreenshot.png

This error doesn't exist when using the Fluent launcher, so I have a hard time believing I need to install the "Hydra Service". That leads me to believe there's an issue with my host file, but I've followed these instructions, and I can't see any issues.

Does someone happen to know why an issue like this could be occurring? Or, know of a tutorial or document which describes how to open Fluent via the command line and connect to Linux HPC resources (I couldn't find this specific issue in the Fluent User's Guide)? By the lack of what I'm finding online about Fluent's exclusivity, it seems like this issue isn't very common when using an HPC so I could also be completely off base here.

If it helps, I've attached screenshots of how I can successfully connect with the Fluent launcher. Any help would be greatly appreciated, thanks!
RemoteTabScreenshot.jpg
SchedulerTabScreenshot.jpg

comiskeyp · April 16, 2025, 09:37

Upon further testing I've found that the command line options listed in Section 4.1.5 of V24R2 User's Manual do not describe an option to launch Fluent from the Windows Command Prompt remotely connected to a Linux HPC with a scheduler. The listed platform for the command options in Table 4.1 therein are not for which platform the command can be applied to, but only which platform you can use those options on.

In other words, I don't understand the use of the undocumented command "-scheduler_exclusive=0" if you can't specify the Slurm scheduler in Windows.

April 10, 2025, 09:48	Exclusivity Issue Running Fluent Using Linux HPC Resources	#1
comiskeyp New Member Patrick Comiskey Join Date: Apr 2025 Posts: 2 Rep Power: 0	Hi Everyone, My goal is to run Fluent from a Windows workstation using Linux HPC resources and following these instructions, I'm successfully able to do this when I use the Fluent launcher. However, Fluent by default runs exclusively on a node which creates an issue when another HPC user is using only a few CPUs on that node. It results in a very long queue time (our scheduler is Slurm) because Fluent will simply not spawn on the remaining CPUs of that node until the other user is done. As a result, I've been looking for a remedy and came across an undocumented command on an Ansys help forum, "-scheduler_exclusive=0", which turns off this default exclusive behavior. The problem I'm having with this is that in order to use the command, I have to launch Fluent with the Windows Command Prompt and I'm receiving an error which I do not get when using the Fluent launcher. When trying to open Fluent (with or without the scheduler, MPI, or interconnect - I get the same result) via the Command Prompt typing: Code: fluent 3ddp -meshing -t8 -cnf=<HOST FILE> I get the following error: ErrorScreenshot.png This error doesn't exist when using the Fluent launcher, so I have a hard time believing I need to install the "Hydra Service". That leads me to believe there's an issue with my host file, but I've followed these instructions, and I can't see any issues. Does someone happen to know why an issue like this could be occurring? Or, know of a tutorial or document which describes how to open Fluent via the command line and connect to Linux HPC resources (I couldn't find this specific issue in the Fluent User's Guide)? By the lack of what I'm finding online about Fluent's exclusivity, it seems like this issue isn't very common when using an HPC so I could also be completely off base here. If it helps, I've attached screenshots of how I can successfully connect with the Fluent launcher. Any help would be greatly appreciated, thanks! RemoteTabScreenshot.jpg SchedulerTabScreenshot.jpg

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April 16, 2025, 09:37		#2
comiskeyp New Member Patrick Comiskey Join Date: Apr 2025 Posts: 2 Rep Power: 0	Upon further testing I've found that the command line options listed in Section 4.1.5 of V24R2 User's Manual do not describe an option to launch Fluent from the Windows Command Prompt remotely connected to a Linux HPC with a scheduler. The listed platform for the command options in Table 4.1 therein are not for which platform the command can be applied to, but only which platform you can use those options on. In other words, I don't understand the use of the undocumented command "-scheduler_exclusive=0" if you can't specify the Slurm scheduler in Windows.