Actually, the fundamental reason for the existence of r/c/stride/count is the very bad efficiency of plot_surface (you can look up the old issues for that). Do your earlier changes improve the situation enough to make r/c/stride/count unnecessary anymore from a performance POV? If so, another option could be to just deprecate them (the user can still manually downsample their array if they really want such an effect, as for imshow() or any other 2d plotting function).

Yeah, honestly I don't fully understand why is it the responsibility ofplot_surface to do the downsampling, since it shouldn't bethat difficult to do for the users. On the other hand, it is a bit annoying to downsample while making sure that you still cover the full range of the plot (that's the reason this PR even has to exist). I don't have all the context here, so it's likely best to leave this decision to you or other core developers, but I'm happy to run some benchmarks comparing the performance before and after my PRs if you can come up with some good test cases and conditions under which those arguments should no longer be necessary.

Also note that while my PR speeds up the whole preprocessing/projection pipeline, there are still significant overheads in path creation and processing in the backends because this code is not batched at the moment. Striding certainly limits the number of paths that have to be constructed, so it might still be quite a bit faster to do it this way.

To me it would be very interesting to try to push backends closer to the possible perf limits. It is quite unreasonable that my PC can render graphics in latest games in 4k resolution at 60fps, but needs a second to draw a surface plot on an 800x800 grid. Interestingly enough I've tried multiple other Python packages for drawing but none of them had good performance for my use case, and matplotlib seemed like the one that would be the easiest to patch.

If you look at the old discussions, some devs thought that plot_surface should not be in charge of the downsampling, but the perf was so bad that it was left in. We could revisit this now, though...
(In think I'd rather leave this specific PR for until all other optimizations go in, so that we can better evaluate the need for it.)

Sure, I agree that this should wait.

#16675 has landed, so this is unblocked now.

Should we also wait for#16688 and#16689 first?

The full benefit of this PR won't be realized until#16688 and#16689 land, but it still provides significant speedups for the slow path inplot_surface on its own. All of those PRs have benefits of their own, but they're magnified when you apply them all. There's no particular order in which they have to get merged.

The point is, we could consider merging all others, and then, if the global speed is improved enough, just deprecate {r,c}{count,stride}.

Sure. As I've said they're independent so I'm ok with landing them in any order you like. We can wait for the other PRs for now.

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After implementing the other plot_surface speedups, this is what the profiler looks like for a 1000x1000 surface plot:

The patching routine here is a very small fraction of the overall runtime, which is dominated by drawing. It's also a one-time cost which won't be re-incurred during plot interaction. And when I test the new code, there is minimal improvement in the speed of that part of the routine (it's still operating with a list comprehension).

So I think this is very low impact, and since this PR is orphaned am closing as won't do. The good news is that the other recent speedups to 3D plotting have resulted in a significant improvement to plot_surface without this change.