1. CSV Overflow Panic: Use saturating_sub to prevent underflow when total_failed_paths > n
2. Heuristic Scale Mismatch: octile_distance_3d now divides by ITILE_SIZE to match g-score units
3. Goal Z Offset: Correct target.as_ivec3() - ivec3(0,0,1) not ITILE_SIZE (target already has +1.0)
4. Gravity Yo-Yo: Clear current_path and target when entity falls to prevent teleportation loop
The async pathfinding with StandableBitGrid caused massive lag due to synchronous
bounding box calculation in the main thread (millions of hashmap lookups for long paths).
Additionally, the splicing logic had a catastrophic bug where it applied a single
finished path to ALL entities unconditionally.
Solution:
- Revert to thread-local synchronous A*
- Implement PathRequestQueue to process max 8 paths per frame
- Keep provisional paths for immediate movement
- Since entity walks provisional path, full path calculates from current position,
eliminating the need for complex splicing logic.
The is_standable_tile(goal) check was causing failures when goal position
wasn't directly standable (common case). A* doesn't require goal to be
standable - it finds the best path it can. Removed the check and return
fallback single-point path when start isn't standable.
Provisional paths were not being recorded to benchmark stats, causing
total_paths=0 while failed_paths accumulated. Now records:
- path_calc_times_us (timing)
- path_lengths (path length)
- nodes_expanded (A* nodes visited)
- failed_paths (when start/goal not standable)
The condition 'if ambulatory.current_path.is_none() || pending_async.is_some()' was backwards.
It should skip entities that ALREADY have a path, not entities WITHOUT a path.
Fixed to properly skip entities with existing paths or pending async tasks.
- Restored original target selection logic that validates is_standable_tile
- Fixed target position z-level checking (check floor tile then standable)
- Re-added check for completed paths (path_index >= path.len)
- This was the cause of 50,297 failed paths - entities targeting invalid positions
Key fixes based on benchmark analysis:
1. Remove TIER0 Vec-based pathfinding - O(N) linear scan was slower than FxHashMap for typical path lengths
2. Consolidate scratchpads into single AStarScratchpad struct - eliminates nested RefCell borrow overhead
3. Remove Arc wrapper from TileMap - eliminated Copy-on-Write trap causing 63ms stutters
4. Replace AHashMap with FxHashMap - FxHash is faster for small integer keys like IVec3
5. Simplify tier logic - single pathfinding function with scratchpad reuse
Benchmark analysis showed:
- Original: 1.95 µs/node, P99 1.1ms, Max 5ms
- TIER0/TIER1 regression: 2.89 µs/node (+48%), P99 5ms (+348%)
- Root causes: Vec linear scan in TIER0, nested RefCell borrows, Arc::make_mut CoW
This should restore and improve performance by using simple FxHashMap scratchpad for all paths.
- Replace std HashMap (SipHash) with ahash::AHashMap for fast non-crypto hashing
- Pack tile data from tuples to structs: FloorTileData (~35 bytes) and FixtureTileData (~18 bytes)
- FloorTileData: pack 3 bools into single flags byte, use u8 for id/weight
- FixtureTileData: pack 2 bools into single flags byte
- Update all accessors: is_standable_tile, visibility, terrain generation, forestry
- Preparation for async pathfinding (Arc wrapping to come in follow-up)
Memory reduction: ~54% for floor tiles (76→35 bytes), ~62% for fixtures (48→18 bytes)
Hash performance: AHashMap uses fxhash, faster than SipHash for game data
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