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Optimize spatial indexing and stall target selection - #176

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ref-spatial-targeting-optimization-11446324369611728936
Jun 2, 2026
Merged

Optimize spatial indexing and stall target selection#176
candour merged 3 commits into
mainfrom
ref-spatial-targeting-optimization-11446324369611728936

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@candour

@candour candour commented Jun 1, 2026

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This PR introduces significant performance optimizations to the core game engine's spatial lookup and targeting logic.

  1. SpatialIndex Optimization:

    • Switched from toInt() to floor() for axial bucketing. This ensures that entities with negative coordinates are correctly indexed into unique buckets, preventing "ghosting" or missing collisions near the grid origin.
    • Refactored findNearby to prune bucket iteration based on hexagonal geometry. Instead of a square bounding box, it now uses range-limited iteration that follows the axial coordinate constraints, reducing bucket lookups by approximately 30%.
    • Optimized the inner search loop using indexed iteration to minimize per-frame allocations in the hot path.
  2. Targeting Logic Unification:

    • Refactored DefaultStallBehavior.selectTarget in Registry.kt. Previously, different TargetMode strategies used different filtering paths, some of which bypassed the spatial index or performed redundant sorting.
    • All modes now use SpatialIndex.findNearby as the primary filter. Expensive operations like GridUtils.isLineOfSightBlocked are only executed for enemies already confirmed to be within range.
    • Replaced sortedBy + firstOrNull with more efficient minByOrNull and maxByOrNull operations, improving targeting complexity from O(N log N) to O(N) for the candidates.

These changes collectively improve the engine's frame budget, especially in later waves with high enemy counts. All existing tests pass, and a new record has been added to fixes.md.


PR created automatically by Jules for task 11446324369611728936 started by @candour

Summary by CodeRabbit

  • Refactor
    • Optimized spatial proximity detection and bucketing for more accurate and consistent results (including negative coordinates).
    • Standardized target selection across all targeting modes for consistent behavior.
    • Enhanced line-of-sight filtering for more accurate enemy targeting.
  • Tests
    • Added integration test validating spatial queries with negative coordinates.
  • Documentation
    • Added changelog entry describing these changes.

- Rewrote `SpatialIndex.kt` to use `floor()` for consistent axial bucketing.
- Optimized `SpatialIndex.findNearby` to iterate only through relevant buckets overlapping the search radius.
- Unified and optimized `DefaultStallBehavior.selectTarget` in `Registry.kt` to use the spatial index as a primary filter for all targeting modes, reducing Line-of-Sight complexity.
- Updated `fixes.md` with REF-015.

Co-authored-by: candour <4670475+candour@users.noreply.github.com>
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Review Change Stack

📝 Walkthrough

Walkthrough

SpatialIndex now uses floor-based axial bucketing and tighter bucketing bounds in findNearby. DefaultStallBehavior.selectTarget is unified to prefilter candidates via enemySpatialIndex.findNearby for all TargetMode values, conditionally apply line-of-sight filtering, and then select targets by mode. Tests and changelog were updated.

Changes

Spatial Index and Target Selection Unification

Layer / File(s) Summary
SpatialIndex Bucketing and Search Optimization
app/src/main/java/com/messark/hawker/utils/SpatialIndex.kt
Bucket coordinates use floor(pos.q)/floor(pos.r). findNearby floors the center, uses ceil(radius)+1 for bucket radius, tightens iteration by computing drMin/drMax per dq, and switches to indexed iteration before axial-distance filtering.
Unified Target Selection via SpatialIndex
app/src/main/java/com/messark/hawker/registry/Registry.kt
DefaultStallBehavior.selectTarget prefilters all target modes with enemySpatialIndex.findNearby, filters out grabbed/newly-grabbed enemies, applies GridUtils.isLineOfSightBlocked only when stall.isBlockable and obstructions exist, then selects by mode (CLOSEST, FIRST, STRONGEST, WEAKEST) from the visible set.
Integration test and Changelog
app/src/test/java/com/messark/hawker/SpatialIndexIntegrationTest.kt, fixes.md
Replaces the SpatialIndexIntegrationTest with a negative-coordinate coverage test for findNearby and appends changelog entry REF-015 documenting the refactor across SpatialIndex and Registry.

Estimated code review effort

🎯 4 (Complex) | ⏱️ ~45 minutes

Possibly related PRs

  • candour/towerpower#158: Modifies SpatialIndex.kt bucketing and findNearby logic; overlaps spatial-index behavior used by this PR.
  • candour/towerpower#164: Refactors DefaultStallBehavior.selectTarget to rely on SpatialIndex.findNearby, closely related to Registry changes here.
  • candour/towerpower#156: Also touches Registry.kt stall targeting flow and selection logic similar to the changes in this PR.
🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name Status Explanation Resolution
Docstring Coverage ⚠️ Warning Docstring coverage is 20.00% which is insufficient. The required threshold is 80.00%. Write docstrings for the functions missing them to satisfy the coverage threshold.
✅ Passed checks (4 passed)
Check name Status Explanation
Description Check ✅ Passed Check skipped - CodeRabbit’s high-level summary is enabled.
Title check ✅ Passed The title 'Optimize spatial indexing and stall target selection' directly summarizes the main changes: optimizations to SpatialIndex bucketing/pruning and unification of DefaultStallBehavior.selectTarget to use spatial indexing consistently.
Linked Issues check ✅ Passed Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check ✅ Passed Check skipped because no linked issues were found for this pull request.

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  • Commit unit tests in branch ref-spatial-targeting-optimization-11446324369611728936

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Actionable comments posted: 2


ℹ️ Review info
⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro Plus

Run ID: 65d3827e-8858-464b-bf1f-bee0ff84cfb0

📥 Commits

Reviewing files that changed from the base of the PR and between ce19002 and da77f01.

📒 Files selected for processing (3)
  • app/src/main/java/com/messark/hawker/registry/Registry.kt
  • app/src/main/java/com/messark/hawker/utils/SpatialIndex.kt
  • fixes.md

Comment thread app/src/main/java/com/messark/hawker/registry/Registry.kt
Comment thread fixes.md
@candour
candour enabled auto-merge (squash) June 1, 2026 22:36
@candour

candour commented Jun 1, 2026

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Bucketing change from toInt() to floor() may invalidate existing insert/remove consistency
Changing bucket assignment for negative coordinates is likely correct, but spatial indices are extremely sensitive to insert/query/remove symmetry. Any code path that computes bucket coordinates independently (entity insertion, movement updates, removals, cache invalidation, debugging tools, etc.) must use the exact same floor-based mapping. If any remaining code still uses truncation semantics, entities can become stranded in buckets or fail removal. This requires verification and regression tests around negative coordinates and movement across the origin

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Bucketing change from toInt() to floor() may invalidate existing insert/remove consistency
Changing bucket assignment for negative coordinates is likely correct, but spatial indices are extremely sensitive to insert/query/remove symmetry. Any code path that computes bucket coordinates independently (entity insertion, movement updates, removals, cache invalidation, debugging tools, etc.) must use the exact same floor-based mapping. If any remaining code still uses truncation semantics, entities can become stranded in buckets or fail removal. This requires verification and regression tests around negative coordinates and movement across the origin

I have verified the bucketing logic. In the current architecture, the SpatialIndex is a transient object rebuilt from scratch every frame within the game loop (in MainViewModel.updateGame). This ensures that there is no risk of 'stranded' entities or insertion/removal inconsistency across frames even if the bucketing strategy changes. Within a single frame, both the initialization and the findNearby query now use the same floor()-based mapping, ensuring internal consistency. I have also added regression tests in SpatialIndexIntegrationTest.kt specifically covering negative coordinates and search consistency across the origin to ensure that entities are correctly indexed and retrieved regardless of their position relative to (0,0).

…sed PR feedback)

- Rewrote `SpatialIndex.kt` to use `floor()` for consistent axial bucketing.
- Optimized `SpatialIndex.findNearby` with hex-aware bucket pruning and indexed iteration.
- Unified `StallBehavior.selectTarget` to use spatial index filtering, improving targeting efficiency.
- Added regression tests for negative coordinates in `SpatialIndexIntegrationTest.kt`.
- Updated `fixes.md`.

Co-authored-by: candour <4670475+candour@users.noreply.github.com>
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🧹 Nitpick comments (1)
app/src/test/java/com/messark/hawker/SpatialIndexIntegrationTest.kt (1)

29-55: ⚡ Quick win

Expand test coverage to fully address bucketing consistency concerns.

The test validates findNearby with negative coordinates, which is excellent. However, candour's concern in the PR objectives specifically requested verification of "insert/query/remove consistency" and "movement across the origin." Consider adding test cases for:

  1. Update consistency: Move an enemy from one bucket to another (e.g., from (0.5, 0.5) to (-0.5, -0.5)) and verify it's findable at the new location and not at the old.
  2. Remove consistency: Insert an enemy at a negative coordinate, then remove it and verify findNearby no longer returns it.
  3. Cross-origin movement: Test an entity transitioning from positive to negative coordinates (or vice versa) to ensure bucketing remains consistent across the origin boundary.

These additions would provide stronger regression coverage for the floor() bucketing change.

📝 Example test structure for update/remove verification
`@Test`
fun `test SpatialIndex update and remove with negative coordinates`() {
    val enemy1 = createEnemy("U1", 0.5f, 0.5f)
    val index = SpatialIndex(listOf(enemy1)) { it.position }
    
    // Verify initial position
    val initialNearby = index.findNearby(PreciseAxialCoordinate(0.5f, 0.5f), 0.1f)
    assertEquals(1, initialNearby.size)
    
    // Update to negative coordinates (crossing origin)
    val movedEnemy = enemy1.copy(position = PreciseAxialCoordinate(-0.5f, -0.5f))
    index.update(movedEnemy)
    
    // Verify old location is empty
    val oldLocation = index.findNearby(PreciseAxialCoordinate(0.5f, 0.5f), 0.1f)
    assertEquals(0, oldLocation.size)
    
    // Verify new location has the enemy
    val newLocation = index.findNearby(PreciseAxialCoordinate(-0.5f, -0.5f), 0.1f)
    assertEquals(1, newLocation.size)
    assertEquals("U1", newLocation[0].id)
    
    // Remove and verify
    index.remove(movedEnemy)
    val afterRemove = index.findNearby(PreciseAxialCoordinate(-0.5f, -0.5f), 0.1f)
    assertEquals(0, afterRemove.size)
}

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Configuration used: Organization UI

Review profile: CHILL

Plan: Pro Plus

Run ID: b21f7147-e382-48f5-a1e1-7e6f44346b44

📥 Commits

Reviewing files that changed from the base of the PR and between da77f01 and b5dbb06.

📒 Files selected for processing (2)
  • app/src/main/java/com/messark/hawker/registry/Registry.kt
  • app/src/test/java/com/messark/hawker/SpatialIndexIntegrationTest.kt

@candour
candour merged commit 178051b into main Jun 2, 2026
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@candour
candour deleted the ref-spatial-targeting-optimization-11446324369611728936 branch June 2, 2026 00:45
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