why does multiple gpu not work?

[Shyam Prasad V Atri]

I have a tank which has these dimensions

x [-0.7,0.7]

y[-0.5 0.5]

z[-0.5 0.5]

I am trying to run the simulation with 4gpu and i keep getting error in the simulation. This error is so generic and i dont know why it is causing

Error:QSocketNotifier: Can only be used with threads started with QThread

I have given the correct gpu slicing --multi-gpu-slicing-direction=X but still i get this error

Can anyone suggest why?

[Lucas Bertollo Baggio]

Hello,

does it work for single GPU?

[Shyam Prasad V Atri]

It works for single gpu and two GPU the moment I request 3 GPU or 4gpu the simulation keeps erroring out 

[Lucas Bertollo Baggio]

Rocky works for single-node only. Are all your GPUs in the same node?

[Shyam Prasad V Atri]

Yes they are all on same node and same host 

[Shyam Prasad V Atri]

All 4gpus on same node and one computer. Still it errors out 

[Lucas Bertollo Baggio]

Would you give me more deatails about your case?

 

[Shyam Prasad V Atri]

Its a mixing tank of 1m diameter and 1m height. There is a top inlet pipe of  20cm and bottom outet pipe of 20cm in the x direction hence the total distance covered in x direction ranges from negative 0.7m to positive 0.7m. the pipe diameter is 10cm. I have about 700 sphero cylinder particles made of multiple elements (flexible one)

[Lucas Bertollo Baggio]

What GPUs are you using? Do you have license for using 4 GPUs? 

It also seems like you have very few particles for using 4 GPUs. 

[Shyam Prasad V Atri]

 

I gave 700 as an example… I have 70000 particles I want to add more than that too… I am using L40s or H100 or a100 gpu of University hpc cluster. I believe the universitys acadamic ansys license should allow the use of four gpus. i did not see any restrictions 

 

[Shyam Prasad V Atri]

Hello Lucas, Any idea why such a simulation is not working. Please let me know.

[Lucas Bertollo Baggio]

Try to execute the simulation directly from RockySolver.exe (from ANSYS Inc\v__\rocky\bin), so you might get some extra information about why this is not working. 

[Shyam Prasad V Atri]

 

So do you mean that i should try to run the simulation on GUI insted of script? (I am trying to run on HPC, not a normal computer)

 

[Shyam Prasad V Atri]

So this is what i get

my geometry

I do the slicing in x direction

I get this error

I do the slicing in y direction

i get this error

Please tell me how to fix this

 

[Shyam Prasad V Atri]

I thought memory might be an issue and tried to allocate more memory but it still gives me the same error

[Lucas Bertollo Baggio]

Which Rocky version are you using?

[Shyam Prasad V Atri]

Rocky 2025 r1 (2025.0 academic university version)

[Lucas Bertollo Baggio]

Could you try to reproduce it in Rocky 2025 R2?

[Shyam Prasad V Atri]

i need to ask for the installation on hpc which may take time. is there any way this version can be used? Because changing versions is a time-consuming and painful process. 

[Lucas Bertollo Baggio]

We had a bug with multi GPU that was fixed in 2025 R2. I think that updating Rocky is your best first try!

[Shyam Prasad V Atri]

Hey we are not able to get the installation file for hpc can you please tell us where can we get the installation file from for installing ansys 2025 r2 on hpc