OpenCV Optical Flow Cuda Naiva Implementation Slower then CPU

[cudawarped]

@haider_abbasi

Given the specifications of my rig and the software versions used, what could be contributing to the observed slower performance of the CUDA-based optical flow calculation compared to its CPU counterpart? Especially, if you can highlight why the huge difference between the expected case even for naive implementation.

The naiive implementation (Naive CUDA implementation without pre-alloc, streams or other optimizations)

1. allocates the return arrays on the GPU in each iteration which is costly, and
2. calls cudaDeviceSynchronize (hard sync) on every iteration because you are not passing a cuda stream. As a result the timing will be off if you timed it with the code from that notebook which uses CPU not GPU timers. This due to the synchronization will include the latency (time between calling optFlow.calc and it execution) of every kernel launch.

That said I have no idea if the code will be faster on your RTX 3070 than your Ryzon 7 2700.