extract: scan way nodes once across all extracts in complete_ways pass 1#314
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yuiseki wants to merge 1 commit into
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extract: scan way nodes once across all extracts in complete_ways pass 1#314yuiseki wants to merge 1 commit into
yuiseki wants to merge 1 commit into
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This was referenced Apr 29, 2026
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I understand why this optimization helps for longer ways, going over 2000 way nodes multiple times adds memory accesses which might be outside the memory cache in the CPU. But I wonder whether this is also the case for ways with only a few nodes. Could you try measuring the impact if the old algorithm is used for ways with a small number of nodes? |
joto
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May 10, 2026
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Apart from the variable name and the other comment about short ways this looks good.
| // Default implementation: call eway() for each extract separately. | ||
| // Subclasses may override this to process all extracts in a single | ||
| // pass over way.nodes(). | ||
| void eway_all(std::vector<extract_data>& exts, const osmium::Way& way) { |
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exts -> extracts. No reason to be too stingy with characters in variable names.
| // eway() loop when there are more than 64 extracts. | ||
| // Pass A finds which extracts claim this way. | ||
| // Pass B records all node refs into extra_node_ids for matched extracts. | ||
| void eway_all(std::vector<extract_data>& exts, const osmium::Way& way) { |
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See #312.
In Pass 1 of
--strategy=complete_ways,eway()is called independently foreach extract on every way. This means
way.nodes()is scanned up to twice perextract, giving up to 2N scans total for N extracts.
This adds an
eway_all()override instrategy_complete_waysthat scansway.nodes()at most twice regardless of N. Auint64_tbitmask tracks whichextracts have claimed the way in the first pass; the second pass then records
all node refs into
extra_node_idsfor matched extracts only.When there are more than 64 extracts the method falls back to the original
per-extract
eway()loop.Benchmark
japan-260423.osm.pbf (~1 GB), 8-tile extraction:
planet-260413.osm.pbf (~86 GB), 16-tile extraction:
Output verified to be identical to the upstream result for all tiles.