ENH: Follow ups for the hilbert_distance function

[tastatham]

The hilbert_distance function will shortly be merged into Dask-GeoPandas.
There was several enhancements that were discussed as follow up items, which include:

• To pass the total_bounds argument to hilbert_distance function if this is already pre-computed: ENH: allow to specify known total_bounds for Hilbert/Morton distance #145
• Use the bounds of the spatial_partitions if present. -> ENH: use total_bounds of spatial_partitions if available for Hilbert/Morton distance #161
• Calculating the mid-points for (Multi)Point geometries in _continuous_to_discrete_coords is not necessary:
  • To add a check to see whether the passed geometries are (Multi)Points
  • Only compute the mid-points for non-(Multi)Point geometries.
• Currently the _continuous_to_discrete function clips discrete integer values using base Python because numpy.clip is not currently supported by Numba: (no longer using numba)
  • To add numpy.clip when it's supported by Numba - v0.54
• Data type optimisation should be assessed
  • Total bit-width in _continuous_to_discrete - to use numpy.int32 instead of numpy.int64
• Provide guidance on p parameter that controls precision of resulting Hilbert curve; need to help user understand how to set this themselves / when this can be useful to set this themselves. (also check hackmd notes)
• To add a notebook

Note: Will add permalinks when merged.

[martinfleis]

One more thing to add is to ensure that codecov sees the coverage of numba jitted functions. We'll probably need to run that bit again without that using env variable.

[tastatham]

Another follow up is to centralise/ generalise several functions that are used by both hilbert_distanceandmorton_distance`.

• Firstly, the _continuous_to_discrete_coords function is imported from hilbert_distance.py in morton_distance.py - centralise
• Secondly, the _distances_from_coordinates function is used in both hilbert_distance.py in morton_distance.py but are defined in slightly different ways - generalise

[TomAugspurger]

I didn't follow this implementation closely, but is the plan to rely on the hilbertcurve package long-term? If so, it needs to be added to the install_requires:

dask-geopandas/setup.py

Lines 6 to 11 in 99fa1a8

	install_requires = [
	"geopandas",
	"dask>=2.18.0,!=2021.05.1",
	"distributed>=2.18.0,!=2021.05.1",
	"numba",
	]

.

[martinfleis]

@TomAugspurger We don't depend on it. It is used only in CI. We use the custom numba implementation ported from spatialpandas.