SashegDev
874b6f20c2
Основа — Horizon (MIT). История апстрима не переносится: этот репозиторий ведёт свою.
64 lines
3.7 KiB
Markdown
64 lines
3.7 KiB
Markdown
# World-generation value providers
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Horizon implements the scalar distributions needed by the pinned Java Edition
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**26.3** cave and canyon definitions. `FloatProvider` supports constant, uniform
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and trapezoid distributions. `IntProvider` supports constant, uniform, biased and
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very biased distributions, trapezoids, recursively clamped sources and weighted lists.
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Decoding retains vanilla numeric narrowing, field defaults and validation rules.
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Sampling preserves float operation order, wrapping integer bounds and the number
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of random draws. Symmetric integer trapezoids use vanilla's distinct two-draw
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subtraction path. Constant float codecs normalize both signed zeros to positive
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zero. Invalid random bounds return an error without silently replacing a result.
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Run `python3 tools/test_value_provider_parity.py`. The
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[local report](../benchmarks/rust-value-provider-2026-10-06/scoped-parity.json)
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records **429,920 matching lines per vanilla JAR**, across **504 definitions** and
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**5,040 seeded fixtures**. The suite invokes actual provider codecs, reads declared
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bounds and compares up to 64 samples per valid fixture. Every sample is followed
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by a random long, checking draw consumption as well as output. Both random modes,
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signed zeros, overflow, equal/reversed ranges, negative plateaus, malformed fields,
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duplicate keys and sampling failures are covered.
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Gaussian providers and canonical provider encoding remain pending. A local
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Gaussian-math probe found double-bit differences between the host Rust logarithm
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and the pinned JVM; using the system logarithm directly would not establish exact
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Gaussian parity.
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This scoped comparison does not establish complete carver or world-generation
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parity. Provider definitions use a bounded decoder; nested integer clamps are
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limited to depth 256 and 65,536 total provider nodes.
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## Anchored height providers
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`HeightProvider` supports constant, uniform, biased, very biased, trapezoid and weighted
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heights using all four vertical-anchor kinds. Empty resolved ranges return the
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vanilla fallback without drawing randomness. Very biased heights preserve the
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guarded inclusive draws, while trapezoid heights retain their distinct sampling
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behavior even for symmetric bounds. Anchor resolution and bound arithmetic wrap
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as signed Java integers.
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Run `python3 tools/test_height_provider_parity.py`. The
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[height-provider report](../benchmarks/rust-height-provider-2026-10-06/scoped-parity.json)
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records **507,660 matching lines per JAR**. The suite compares actual
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`HeightProvider.CODEC` parsing and up to 32 samples per valid definition/context,
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with subsequent random longs. It covers all four anchors, ordinary and overflowing
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generation contexts, empty/equal ranges, defaults and invalid inner/plateau fields,
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and anchor-versus-dispatch preference. Warning logs are excluded. Height-provider encoding remains pending.
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## Weighted choices
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Weighted integer and height providers retain entry order, nested providers and
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zero-weight entries. Integer bounds include zero-weight entries even though they
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cannot be selected. Every selection consumes one bounded draw, including a
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singleton of weight one. Total weights must be positive and no greater than
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2,147,483,647; native constructor rejections are recorded as decode errors.
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Rust stores cumulative weights and selects by binary search, avoiding allocation
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proportional to total weight. The differential suites cover totals on either side
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of vanilla's 64-weight selector threshold, maximum and overflowing totals, nested
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choices, malformed entries and exact subsequent random state. Each list is bounded
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to 8,192 entries, with a shared 65,536-node budget across nested provider decoding.
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Unit tests check those allocation limits and reject oversized branching trees.
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