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Merged
merged 1 commit into from
Feb 17, 2025
Merged

Simplify and optimize Hilbert tile ID <-> XYZ conversion #208

merged 1 commit into from
Feb 17, 2025

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ciscorn
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@ciscorn ciscorn commented Feb 14, 2025 •
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I found that we can simplify and optimize the conversion between XYZ tile coordinates and the Hilbert tile IDs.

This optimization is primarily based on the fact that the tile IDs for (zi, 0, 0) are given by the sum of a geometric series with a common ratio of 4.

Related PR: protomaps/PMTiles#527

@ciscorn ciscorn changed the title Optimize Hilbert tile ID <-> XYZ conversion Simplify and optimize Hilbert tile ID <-> XYZ conversion Feb 14, 2025
@ciscorn ciscorn mentioned this pull request Feb 14, 2025
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ciscorn commented Feb 16, 2025

I benchmarked this on Go 1.24 for both amd64 and arm64 architectures:

  • ZxyToId is about 20% faster
  • ParentId is about 2000% faster
Go 1.24

Linux AMD64

pkg: github.com/protomaps/go-pmtiles/pmtiles
cpu: AMD EPYC 7642 48-Core Processor
BenchmarkZxyToIdOriginal-2    	       7	 156841629 ns/op
BenchmarkZxyToId-2            	       8	 131925635 ns/op (1.19x)
BenchmarkIdToZxyOriginal-2    	       1	2449533628 ns/op
BenchmarkIdToZxy-2            	       1	2011963536 ns/op (1.22x)
BenchmarkParentIdOriginal-2   	       3	 388430708 ns/op
BenchmarkParentId-2           	      69	  17235591 ns/op (22.5x)

MacOS ARM64

pkg: github.com/protomaps/go-pmtiles/pmtiles
cpu: Apple M1 Pro
BenchmarkZxyToIdOriginal-8             9         117123093 ns/op
BenchmarkZxyToId-8                    12          96429438 ns/op (1.21x)
BenchmarkIdToZxyOriginal-8             1        1490087625 ns/op
BenchmarkIdToZxy-8                     1        1448143084 ns/op (1.03x)
BenchmarkParentIdOriginal-8            6         172983236 ns/op
BenchmarkParentId-8                  134           8708995 ns/op (19.9x)

@bdon bdon merged commit 8ea4ca3 into protomaps:main Feb 17, 2025
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bdon commented Feb 17, 2025

Nice optimization, thanks for checking the speed!

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bdon commented Feb 17, 2025

v1.25.1 released https://github.com/protomaps/go-pmtiles/releases/tag/v1.25.1

@ciscorn ciscorn mentioned this pull request Feb 17, 2025
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