Add a cycle detector for generic Graphs and mir::Bodys
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This probably doesn't need to be reviewed by @eddyb (I r?-ed out of habit). |
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Maybe r? @Centril |
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r? @oli-obk Some more docs would indeed be great. |
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I added some more docs comparing this depth-first search to the one in Introduction to Algorithms. Hopefully it's easier to follow now. |
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@bors r+ Thanks, that helps |
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📌 Commit c9e4816 has been approved by |
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…i-obk Add a cycle detector for generic `Graph`s and `mir::Body`s Cycle detection is one way to differentiate the upcoming `const_loop` feature flag (rust-lang#52000) from the `const_if_match` one (rust-lang#49146). It would be possible to use the existing implementation of strongly-connected components for this but less efficient. The ["tri-color" terminology](http://www.cs.cornell.edu/courses/cs2112/2012sp/lectures/lec24/lec24-12sp.html) is common in introductory data structures and algorithms courses: black nodes are settled, grey nodes are visited, and white nodes have no state. This particular implementation is iterative and uses a well-known technique where "node settled" events are kept on the stack alongside nodes to visit. When a settled event is popped, we know that all successors of that node have been visited and themselves settled. If we encounter a successor node that has been visited (is on the stack) but not yet settled, we have found a cycle. r? @eddyb
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…i-obk Add a cycle detector for generic `Graph`s and `mir::Body`s Cycle detection is one way to differentiate the upcoming `const_loop` feature flag (rust-lang#52000) from the `const_if_match` one (rust-lang#49146). It would be possible to use the existing implementation of strongly-connected components for this but less efficient. The ["tri-color" terminology](http://www.cs.cornell.edu/courses/cs2112/2012sp/lectures/lec24/lec24-12sp.html) is common in introductory data structures and algorithms courses: black nodes are settled, grey nodes are visited, and white nodes have no state. This particular implementation is iterative and uses a well-known technique where "node settled" events are kept on the stack alongside nodes to visit. When a settled event is popped, we know that all successors of that node have been visited and themselves settled. If we encounter a successor node that has been visited (is on the stack) but not yet settled, we have found a cycle. r? @eddyb
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Rollup of 16 pull requests Successful merges: - #63356 (Issue#63183: Add fs::read_dir() and ReadDir warning about iterator order + example) - #63934 (Fix coherence checking for impl trait in type aliases) - #64016 (Streamline `Compiler`) - #64296 (Document the unstable iter_order_by library feature) - #64443 (rustdoc: general cleanup) - #64622 (Add a cycle detector for generic `Graph`s and `mir::Body`s) - #64689 (Refactor macro by example) - #64698 (Recover on `const X = 42;` and infer type + Error Stash API) - #64702 (Remove unused dependencies) - #64717 (update mem::discriminant test to use assert_eq and assert_ne over comparison operators) - #64720 ( remove rtp.rs, and move rtpSpawn and RTP_ID_ERROR to libc) - #64721 (Fixed issue from #64447) - #64725 (fix one typo) - #64737 (fix several issues in String docs) - #64742 (relnotes: make compatibility section more sterile and fix rustc version) - #64748 (Fix #64744. Account for the Zero sub-pattern case.) Failed merges: r? @ghost
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Cycle detection is one way to differentiate the upcoming
const_loopfeature flag (#52000) from theconst_if_matchone (#49146). It would be possible to use the existing implementation of strongly-connected components for this but less efficient.The "tri-color" terminology is common in introductory data structures and algorithms courses: black nodes are settled, grey nodes are visited, and white nodes have no state. This particular implementation is iterative and uses a well-known technique where "node settled" events are kept on the stack alongside nodes to visit. When a settled event is popped, we know that all successors of that node have been visited and themselves settled. If we encounter a successor node that has been visited (is on the stack) but not yet settled, we have found a cycle.
r? @eddyb