Use linear-space optimal alignment for EditDistance - #2409
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Included review availability: Your plan provides up to 8 included reviews per hour; 6 remain after this review. 📝 WalkthroughWalkthroughChangesThe dense edit-distance matrix is replaced with a linear-space divide-and-conquer algorithm. String comparison rendering now allows more memory and retains larger differing-context windows. Tests cover alignment correctness, large inputs, and updated rendered output. String diffing
Estimated code review effort: 4 (Complex) | ~45 minutes Merge Risk: ⚪ Minimal · up to The PR replaces the dense edit-distance matrix with a linear-space optimal alignment algorithm while preserving edit distance and reconstructed strings; no actionable merge-blocking risk remains after normal checks and review. Sequence Diagram(s)sequenceDiagram
participant FailedStringComparisonRenderer
participant EditDistance
participant EditPathRenderer
FailedStringComparisonRenderer->>EditDistance: calculate distance and edit path
EditDistance-->>FailedStringComparisonRenderer: normalized path and distance
FailedStringComparisonRenderer->>EditPathRenderer: render the path for compared strings
EditPathRenderer-->>FailedStringComparisonRenderer: formatted inline diff
Poem
🚥 Pre-merge checks | ✅ 4 | ❌ 1❌ Failed checks (1 warning)
✅ Passed checks (4 passed)
Full details: Linked Issues checkExplanation The changes satisfy issue [ Full details: Docstring CoverageExplanation Docstring coverage is 28.57% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 14 functions across 2 files. (1 skipped: 1 unsupported.)
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Greptile SummaryThe PR replaces EditDistance's dense Levenshtein matrix with a divide-and-conquer alignment implementation and raises the renderer's bounded computation threshold.
Confidence Score: 4/5The PR appears safe to merge, with a non-blocking encapsulation issue in the mutable cached path returned by calculatePath(). The new alignment implementation has broad correctness and large-input coverage, but callers can now mutate retained path state and make it inconsistent with the cached distance. Files Needing Attention: spock-core/src/main/java/org/spockframework/runtime/condition/EditDistance.java Important Files Changed
Flowchart%%{init: {'theme': 'neutral'}}%%
flowchart TD
A[Failed string equality] --> B{Input product within limit?}
B -- Yes --> C[Construct EditDistance]
B -- No --> D[Trim common prefix and suffix]
D --> E{Reduced product within limit?}
E -- No --> F[Render strings-too-large fallback]
E -- Yes --> C
C --> G[Trim equal boundaries]
G --> H{Base case?}
H -- Yes --> I[Emit edit operations]
H -- No --> J[Compute forward and backward costs]
J --> K[Select optimal midpoint]
K --> G
I --> L[Normalize edit runs]
L --> M[Render distance and alignment]
Reviews (1): Last reviewed commit: "feat:editDistance improvement" | Re-trigger Greptile |
![greptile-apps[bot]](https://avatars.githubusercontent.com/in/867647?s=60&v=4){kind=small}
| public List<EditOperation> calculatePath() { | ||
| LinkedList<EditOperation> ops = new LinkedList<>(); | ||
| int i = seq1.length(); | ||
| int j = seq2.length(); | ||
| int dist = matrix[i][j]; | ||
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| while (i > 0 && j > 0 && dist > 0) { | ||
| int ins = matrix[i][j - 1]; | ||
| int del = matrix[i - 1][j]; | ||
| int sub = matrix[i - 1][j - 1]; | ||
|
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||
| if (dist == ins + 1) { | ||
| addOrUpdate(ops, INSERT, 1); | ||
| j--; | ||
| } else if (dist == del + 1) { | ||
| addOrUpdate(ops, DELETE, 1); | ||
| i--; | ||
| return path; | ||
| } |
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calculatePath() now returns the constructor-cached mutable list, whose EditOperation elements also expose incLength(). Modifying that result corrupts subsequent paths while getDistance() retains its original value, producing inconsistent diagnostics or invalid operation lengths during rendering.
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Alright, I changed it so calculatePath() returns now a new list
![coderabbitai[bot]](https://avatars.githubusercontent.com/in/347564?s=60&v=4){kind=small}
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Actionable comments posted: 1
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Inline comments:
In
`@spock-core/src/main/java/org/spockframework/runtime/condition/EditDistance.java`:
- Line 72: Update calculatePath() to return a defensive copy of the mutable path
rather than the shared path instance, ensuring callers can modify their result
without affecting subsequent calls.
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ℹ️ Review info
⚙️ Run configuration
Configuration used: Organization UI
Review profile: CHILL
Plan: Pro Plus
Run ID: cc8e0f14-82e6-42af-90ad-ad7074e8a784
📒 Files selected for processing (8)
spock-core/src/main/java/org/spockframework/runtime/FailedStringComparisonRenderer.javaspock-core/src/main/java/org/spockframework/runtime/condition/EditDistance.javaspock-specs/src/test/groovy/org/spockframework/runtime/condition/EditDistanceCrossCheckSpec.groovyspock-specs/src/test/groovy/org/spockframework/runtime/condition/EditDistanceLargeInputSpec.groovyspock-specs/src/test/groovy/org/spockframework/runtime/condition/EditDistanceSpec.groovyspock-specs/src/test/groovy/org/spockframework/runtime/condition/EditPathRendererSpec.groovyspock-specs/src/test/groovy/org/spockframework/smoke/condition/StringComparisonRendering.groovyspock-specs/src/test/groovy/org/spockframework/smoke/mock/TooFewInvocations.groovy
💤 Files with no reviewable changes (1)
- spock-specs/src/test/groovy/org/spockframework/runtime/condition/EditDistanceSpec.groovy
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1 participant
Closes #2408
Replace the dense Levenshtein matrix in EditDistance with a Myers-Miller/Hirschberg-style divide-and-conquer algorithm.
This also resolves the long-standing EditDistance implementation TODO to use an algorithm with lower time and/or space complexity.
The new implementation:
The computation limit is increased from 50 Ki cells to 1 Mi cells. It now primarily limits CPU work rather than protecting against allocation of a dense matrix. Completely different strings above the limit still use the existing fallback message.
Rendering changes
Multiple optimal Levenshtein alignments can exist. The divide-and-conquer algorithm may select a different optimal path from the previous matrix backtracking implementation.
Expected failure messages affected by this tie-breaking have been updated. The distance and reconstructed strings remain unchanged.