Convert Tracker structs to columnar#762
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frankmcsherry merged 2 commits intoTimelyDataflow:masterfrom Mar 13, 2026
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Seems alright, but I wonder if we could push it further to flatten even more. We already have to pay for an increase in complexity, so why stop here?
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| /// Internal operator connectivity, columnar form of `Vec<Vec<PortConnectivity<T::Summary>>>`. | ||
| /// Indexed by `(node, input_port)` to yield `(output_port, summary)` pairs. | ||
| nodes: Vecs<Vecs<Vec<(usize, T::Summary)>>>, | ||
| /// Edge connectivity, columnar form of `Vec<Vec<Vec<Target>>>`. | ||
| /// Indexed by `(node, output_port)` to yield target slices. | ||
| edges: Vecs<Vecs<Vec<Target>>>, |
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Since we're flattening this .. what about flattening it further? Instead of nested vecs, have the usual index vec + flat vector, one for each level. I can imagine it'll get unwieldy for no benefit, but maybe worth exploring.
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Vecs is what you are thinking of! :D
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It could maybe be clearer as <Vec<Vec<PortConnectivity<T::Summary>>> as Columnar>::Container, but you can't quite get there yet (w/o T::Summary: Columnar>).
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This PR is largely authored by Claude, as a way to convert the types in the reachability tracker to have columnar layouts, rather than deeply nested short vectors and allocations. The types are all dense integer indexed (nodes, ports), and standard columnar vector layouts work great here.
The win is that at runtime there is less memory to hop through to reach path summaries, among other things. There is a bonus benefit that large graphs will not take as long terminating; the deallocation has taken seconds on large benchmarks.