OPM FLOW - GPU ACELERATION

[EnriqueRamonV]

I am a user of OPM Flow and am interested in optimizing its performance by utilizing the GPU in my system. Could you please confirm if it's possible to activate GPU acceleration for calculations in OPM Flow, and how I can do so? Are there specific settings within the software that I need to adjust?
I appreciate any guidance or additional documentation you can provide on this matter.

Best regards,
Enrique Ramon

[multitalentloes]

It is possible both for Nvidia and AMD cards, but note that only parts of the simulator is currently gpu-accelerated. In addition to this, there is no guarantee that running a simulation on your GPU will be faster. As of now you typically need a quite large simulation for GPUs to be faster, and hard simulation cases are usually also better on CPU because more fancy numerical algorithms have been implemented.

The main part of OPM currently supported by GPUs is the linear solver. So to make sure I run my simulation with a GPU I provide a json file that describes the linear solver using the --linear-solver=/path/to/file.json option. The json may look something like this:

{
   "tol": "0.01",
   "maxiter": "200",
   "verbosity": "0",
   "solver": "gpubicgstab",
   "preconditioner": {
       "type": "GPUDILU"
   }
}

Here the important part is to set the solver to "gpubicgstab", which is a conjugate gradient method.
You should also select a preconditioner, right now probably "GPUDILU", or "OPMCUILU0".

I know there are other ways to run OPM with GPUs, for instance through the BDA bridge, but I am not very familiar with how to do that.

Note that for the preconditioners to be found OPM must be built with CUDA available if you want to run on an Nvidia GPU, and built with HIP available + CONVERT_CUDA_TO_HIP=ON to make cmake generate the equivalent HIP code that can be run on AMD GPUs.

Feel free to ask more questions if this is still unclear:)

Edit: if your version of opm is older than september 2024 then the solver should be called cubicgstab and the preconditioners should typically start with "CU" instead of "GPU"