OpenGL multi-GPU support

Question

When we create the OpenGL context on PC, is there any way to choose which physical device or how many devices are used? Do the latest OpenGL (4.5) APIs support multi-GPU architecture? If I have two identical graphics cards (for example, two Nvidia GeForce cards), how do I properly program the OpenGL APIs in order to get benefits from the fact that I have two cards? How do I transfer the OpenGL program from a single GPU version to a multi-GPU version with minimal efforts?

Answer 1

OpenGL drivers expose multiple GPUs (in Crossfire/SLI configurations) as if they were a single GPU. Behind the scenes, the driver will (theoretically) figure out how to dispatch rendering calls efficiently between the two GPUs. There are several methods for doing so, and you have zero control over which mechanism a driver picks.

If you want more direct control over which GPU is associated with which GL context, you have to use vendor-specific extensions. AMD has WGL_AMD_gpu_association, while NVIDIA has WGL_NV_gpu_affinity.