[autograd]

It's easy to "trivially know" because it's really expensive to disprove the statement, so you continue believing in your original one.

I am not in game development, but was recently looking in some deep learning networks. A lot of compute, bazillion layers of abstractions (erm python), but at the end of the day, 98% of the time was really spent calculating the matmul. I had luck that it was easy to check it and estimate the abstraction cost (not into great detail), and disprove my original thought.

Had i not checked it, I'd still trivially know that far more perf loss happened because of abstractions.