PERF: Optimize for single point in Geod fwd/inv functions

[greglucas]

This adds a fast-path for scalar inputs by trying out a double-only implementation, and falling back if any input is not a double. An alternative is to add Geod.fwd_point() and Geod.inv_point() functions as well, but I kind of like this transparent form for simplicity of users only needing one function and only a minor overhead for arrays where you are already going through some slower paths.

A little under 10x improvement for scalars.

In [1]: from pyproj import Geod

In [2]: g = Geod(ellps="WGS84")

In [3]: %timeit g.fwd([0], [0], [1], [1])
4.76 µs ± 28.5 ns per loop (mean ± std. dev. of 7 runs, 100,000 loops each)

In [4]: %timeit g.fwd(0, 0, 1, 1)
588 ns ± 4.57 ns per loop (mean ± std. dev. of 7 runs, 1,000,000 loops each)

• Tests added

[codecov]

Codecov Report

Merging #1206 (b752dd9) into main (1e309c2) will decrease coverage by 0.00%.
The diff coverage is 100.00%.

❗ Current head b752dd9 differs from pull request most recent head b93fedf. Consider uploading reports for the commit b93fedf to get more accurate results

@@            Coverage Diff             @@
##             main    #1206      +/-   ##
==========================================
- Coverage   96.28%   96.27%   -0.01%     
==========================================
  Files          20       20              
  Lines        1803     1801       -2     
==========================================
- Hits         1736     1734       -2     
  Misses         67       67              

Impacted Files	Coverage Δ
pyproj/geod.py	97.54% <100.00%> (-0.03%)	⬇️

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[snowman2]

Nice! I am starting to think that following this pattern in #1204 may make sense as well.

[greglucas]

I think it would be nice to add this pattern to the transform() call as well in #1204. Then downstream users wouldn't need to call a separate function at all and their code would benefit immediately. In addition though, since there is a separate PROJ function for this, do you want to still expose it as transform_point() or just leave that as an implementation detail within transform()?

[snowman2]

My main hesitation to merge is the amount of code added versus the amount of code tested. The tests you added are a good start. However, I am thinking it may be a good idea to update the fwd/inv geodesic tests with the scalar_and_array fixture before merging this.

[snowman2]

Thanks @greglucas 👍

[greglucas]

👍 Thanks, @snowman2!

FYI that this all works really nicely over on Cartopy without any update needed to the code at all. The benchmark case I was running went from 7s on pyproj==3.4 to 1.1s on pyproj==main so roughly 6-7x improvement!

[snowman2]

That's great 🎉

[dopplershift]

Thanks for doing all this @greglucas !