russell@unturf.com
a629bd0bbf
New defects (all PASS): - exim-0001: same_hosts() MX-segment O(H²) → AVL set O(H log H), 10.5x at H=20 - minecraft-0001: DependencySorter.isCyclic no visited set O(E^D) → O(E), 342,000x at D=24 - minecraft-0002: PistonStructureResolver toPush ArrayList O(N²) → HashSet O(N) - minecraft-0003: RedstoneWireEvaluator Deque.contains O(N²) → HashSet O(N) - minecraft-0004: MoveThroughVillageGoal visited List O(N²) → HashSet O(N) - mpich-0001: group_lpid_to_rank O(N²) → HashMap O(N), 313x at N=1000 - ompi-0001: group_overlap process-name scan O(N×M) → HashMap O(N+M), 2048x - pcl-0001: RegionGrowing::getSegmentFromPoint O(C×S) → point_labels[] O(1), 50000x CLEAN confirmed: esbuild, express, koa, ktor, lucene, mpich-recvq, ompi-startup, prosody, roda, rust/rustc-wave2, signal-server, solana, wiredtiger, wireguard-tools, linux-kernel (pointer to linux/)
1.4 KiB
1.4 KiB
Classification
| Field | Value |
|---|---|
| CWE | CWE-407 Inefficient Algorithmic Complexity |
| Severity | MEDIUM |
| Component | net/minecraft/world/level/block/piston/PistonStructureResolver.java |
| Function | resolve() BFS loop |
| Hot path | Called every piston activation event |
Defect
PistonStructureResolver.toPush is an ArrayList<BlockPos>. During piston
BFS, toPush.contains(pos) is called for every candidate block — O(N) scan
per call, inside the BFS loop: O(N²) total.
// BEFORE — O(N²): ArrayList.contains() inside BFS loop
private final List<BlockPos> toPush = Lists.newArrayList();
// ...
if (!this.toPush.contains(pos)) {
this.toPush.add(pos);
}
At the 12-block push limit toPush is bounded, but the pattern propagates to modded environments with higher push limits.
Fix
Add a parallel HashSet<BlockPos> for O(1) duplicate detection.
// AFTER — O(N): HashSet.add() returns false on duplicate → O(1)
private final List<BlockPos> toPush = Lists.newArrayList();
private final Set<BlockPos> toPushSet = new HashSet<>();
// Replace: if (!this.toPush.contains(pos)) { this.toPush.add(pos); }
// With: if (this.toPushSet.add(pos)) { this.toPush.add(pos); }
The List is retained for ordered iteration (piston push order matters).
The Set is used only for membership testing.