Ludovic Marie
68 lines
4.5 KiB
Markdown
68 lines
4.5 KiB
Markdown
# Reuse numeric scratch vectors in visibility tests
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A game allocation profile found temporary vectors in the pinned Entity Culling
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1.11.2 visibility library. Its visibility check creates a direction vector, then
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normalizes it; its ray intersection creates a second vector for reciprocals.
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These vectors remain within the calculation and carry only numeric values.
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The opt-in hook redirects those two constructors to separate vectors owned by
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that culling instance. All three components are reset each time. Upstream
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normalization, division, intersection, traversal, caches and decisions stay in
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place. No approximation, ray limit, global pool or shared scratch object is added.
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The instance already keeps mutable camera, target, hit-block and cache state;
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the hook retains that single-caller contract. It does not make an instance safe
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for concurrent or reentrant calls. Two retained numeric objects per instance
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replace temporary objects on this path.
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Use `culling-rays` for an isolated comparison with `m2-balanced`. Graphics, LOD
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radius, worker budget and other controller settings match. All other profiles,
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including the combined foreground experiments, explicitly keep this hook off.
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It only applies to Entity Culling 1.11.2. To disable, set `enabled=false` in
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`config/horizon-culling-rays.properties` and restart. Frame reports record the
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actual `culling_ray_scratch` state; the CLI and offline viewer disclose changes
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in that state.
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`python tools/test_culling_rays.py` runs the publisher's actual geometry with the
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hook disabled and enabled. It compares boolean and provider-query digests for
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12,800 bounding-box checks across eight occluder patterns and two interleaved
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instances. Each mode performed the same 105,239 block reads. It also checks
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2,197 direct ray cases covering signed zero, tiny and large values, infinities
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and NaN, unchanged input vectors, separate instance scratch objects and retained
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arithmetic values. The test uses private fixture invokers; its JAR and accessors
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never enter a release pack. These cases support this workload's equivalence,
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rather than proving every world's rendered pixels or every mod callback.
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A local warmed loop of two million visibility checks allocated 24,318,096 bytes
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with the original constructors versus 920 with scratch reuse. Single caller CPU
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observations were about 167 versus 149 ms. Another unchanged run allocated only
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6,259,360 bytes, illustrating how JIT compilation and escape analysis vary during
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these loops. No fixed per-check allocation or statistical speedup is inferred.
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The independent Linux CI run allocated only 1,040 bytes upstream versus 920
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with scratch reuse, and its caller CPU observation was about 102 versus 119 ms.
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That run provides no useful allocation reduction and is slower in this loop.
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The hook therefore stays isolated and disabled in every recommended profile.
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Raw [local](../benchmarks/culling-rays-2026-10-04/local-applied-hooks.json) and
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[CI](../benchmarks/culling-rays-2026-10-04/linux-applied-hooks.json) observations
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include source and workflow provenance. This is not a whole-game FPS/RAM or Mac
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GPU benchmark; repeated real hardware comparisons and live allocation profiles
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are required.
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A fixed-order live Linux software-rendering pair observed about 28.18 KB/s
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allocated by `CullThread` with the hook off and 27.96 KB/s with it on, over
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roughly 64-second counter spans. This does not establish a useful reduction.
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Allocation samples were dominated by whitelist iteration; the recorded stacks
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did not include either ray constructor. The separate `culling-empty` experiment
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addresses that observed path. The clean 120-second frame captures produced
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599 control and 584 candidate frames, with zero exclusions and matching CSV
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counts; captured graphics and worker settings matched except the ray flag.
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Both worlds saved and exited without crash reports or remaining game processes.
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The outer control launcher returned 143 without exposing the game exit status;
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that return is not counted as a verified normal game exit. Selected
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[live observations](../benchmarks/culling-rays-2026-10-04/live-observations.json)
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retain the recording limits. These are per-thread diagnostic observations, not
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retained memory, a statistical comparison, or a Mac result.
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The factory hook follows the upstream [Mixin constructor redirect contract](https://github.com/SpongePowered/Mixin/blob/master/src/main/java/org/spongepowered/asm/mixin/injection/Redirect.java).
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Compilation uses a checksum-verified publisher JAR; the release mod contains only
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original Horizon classes. Profiles without Entity Culling must still load.
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