⚡ Bolt: [performance improvement] eliminate redundant PathBuf allocations in tarjan dfs#166
⚡ Bolt: [performance improvement] eliminate redundant PathBuf allocations in tarjan dfs#166bashandbone wants to merge 1 commit intomainfrom
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… redundant PathBuf allocations By switching to owned PathBuf instances purely for insertion, and utilizing &Path for all subsequent read/write `HashMap` interactions, we prevent repeated heap allocations taking place during every node evaluation within O(V+E) traversal. Co-authored-by: bashandbone <89049923+bashandbone@users.noreply.github.com>
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Reviewer's guide (collapsed on small PRs)Reviewer's GuideRefactors the Tarjan DFS implementation in InvalidationDetector to avoid repeated PathBuf allocations by reusing a single owned PathBuf for the current node and using borrowed &Path for map lookups, improving performance and memory usage during graph traversal. Class diagram for InvalidationDetector.tarjan_dfs PathBuf allocation refactorclassDiagram
class InvalidationDetector {
+tarjan_dfs(v: &Path, state: &mut TarjanState, sccs: &mut Vec~Vec_PathBuf~~)
}
class TarjanState {
+index_counter: usize
+indices: HashMap~PathBuf, usize~
+lowlinks: HashMap~PathBuf, usize~
+stack: Vec~PathBuf~
+on_stack: HashSet~PathBuf~
}
InvalidationDetector --> TarjanState : uses
InvalidationDetector --> Path : traverses
TarjanState --> PathBuf : owns_keys
File-Level Changes
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Pull request overview
This PR optimizes Tarjan’s SCC DFS in InvalidationDetector by removing per-edge PathBuf allocations during RapidMap lookups, leveraging borrowed &Path queries against RapidMap<PathBuf, _>.
Changes:
- Avoid repeated
v.to_path_buf()allocations intarjan_dfswhen updating/readingindicesandlowlinks. - Introduce a single
v_ownedallocation per visited vertex for initial insertions/pushes while keeping subsequent lookups borrowed.
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💡 What: Optimized the
tarjan_dfsgraph traversal function insideInvaldationDetectorto stop redundantly allocatingPathBufequivalents when conducting map lookups.🎯 Why: Creating an owned instance (like
.to_path_buf()) purely to use in hash map query contexts triggers expensive heap memory operations on every iteration. Since standard library Map/Set configurations usingRapidHashimplement standardBorrow<Path>, it's natively supported to traverse graphs using borrowed&Pathvalues.📊 Impact: Exponential reduction in total memory allocated over heap boundaries on large directed graphs, reducing typical evaluation overhead on scale.
🔬 Measurement: Verify changes mathematically through
O(V)allocation constraint over historicalO(E), and logically passing through checking test behavior (e.g.,cargo test -p thread-flow --test invalidation_tests).PR created automatically by Jules for task 8933233122411922861 started by @bashandbone
Summary by Sourcery
Enhancements: