Using Arena, there is no option to use more than one GPU. I recompiled the source to default to use GPU:0,1 but that is not a fix for everyone else. Here is an image that shows the options that Arena knows about:
Suggested default: Scan the system for GPUs and use all of them that make sense.
E.g. If there are three Nvidia RTX3090 GPUs and some weak on-board GPU, choose the three NVIDIA GPUs as default.
IMO-YMMV
Using Arena, there is no option to use more than one GPU. I recompiled the source to default to use GPU:0,1 but that is not a fix for everyone else. Here is an image that shows the options that Arena knows about:
Aside : this net is kicking butt and taking names in my current Ceres tests. You might like to give it a try. https://training.lczero.org/get_network?sha=9c69ba1f8f5f602804789a8d1c8e62df10953f1e36376ea3296aa56f2a8e61e2 Only 100 games complete out of 6000 scheduled, but it is totally dominating so far.