Does OpenACC take away from the normal GPU Renderi

Question

I'm trying to figure out if I can use OpenACC in place of normal CPU serial execution calls. Usually my programming is all about 3D programming, or uses the GPU normally in some way. I.E. Image processing, or some other type of rendering that requires the use of shaders. I'm trying to figure out if this Library would benefit me or not.

The reason I ask this is because if I'm rendering 3D Graphics (as fast as possible) would it slow down that process in away? Or is it able to maintain it's (in theory) "high frame rates" or not.

If so, what's the trade off, and how much? I'm not willing to loose 3D Graphics (display) performance to enhance operations that can be done on the CPU serially.

Edit: This is a C++ context.

Answer 1

On the AMD and NVIDIA GPUs that I am familiar with, OpenACC programs will make use of compute resources that would also be used to some degree by shader programs. There are many other pieces of graphics hardware in a GPU that are not shared between compute and graphics, but there are some shared resources. Likewise, the GPU may be connected to the system by PCIE, and so this can also present a shared resource or contention point (however it's the rare compute or graphics program that would even come close to using up the bandwidth of a modern Gen3 x16 PCIE connection.)

So if you were using both graphics (or compute) shaders, as well as OpenACC acceleration, there would be contention for resources, to some degree. The level of contention, or the trade off, is not something that I can generalize about. It will depend very much on the specifics of your program, and the extent and the detail sequencing of the compute functions and the graphics functions.

GPU designers have these types of use-cases in mind, and so GPUs are generally pretty good at rapid context switching between the various tasks that may compete for resources.