DBot/overdrive_that_matters
DBot/overdrive_that_matters
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Update commentary on otmRandom

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DBotThePony 2025-03-15 10:08:02 +07:00
parent b7b2b8095c
commit 42386e1fbe
Signed by: DBot
GPG Key ID: DCC23B5715498507
1 changed files with 18 additions and 6 deletions
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src/main/kotlin/ru/dbotthepony/mc/otm/core/IMatteryLevel.kt
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@ -5,13 +5,25 @@ import net.minecraft.world.level.Level
import net.neoforged.fml.ModList
interface IMatteryLevel {
/**
* OTM provided [RandomSource], which has better statistical parameters
*
* Original Minecraft use LCG, which may show bad behavior when repeatedly sampled *a lot*,
* which is what [Level]'s random is used for. OTM provided PRNG should behave better in this scenario.
*/
val otmRandom: RandomSource?
}
/**
* OTM provided [RandomSource], which has better statistical parameters
*
* Original Minecraft use LCG, which may show bad behavior when repeatedly sampled *a lot*,
* which is what [Level]'s random is used for. OTM provided PRNG should behave better in this scenario.
*
* The way OTM uses random generator in its code will quickly cause LCG used in Minecraft to show its bias
* because LCG in minecraft samples its highest 48 bits, which gives us at best 2^16 period in the lowest bit returned by LCG.
* Which it doesn't sound bad, it quickly causes RNG become biased the quicker/more it is sampled on each tick, especially considering
* some may use `level.random.nextInt(chance) == 0` to determine chance of something happening,
* which will get extremely biased on heavy RNG congested environment
* If we avoid sampling Level's generator this much, we won't suffer from bias in our own code, as well as avoid biasing other mods this much.
*
* The "2^16 period" problem is also might be the reason why Entities get their own instance of RandomSource,
* and Mob Goals use random exactly the way described above (`nextInt(chance)`), which can and will suffer
* from bias the moment mob exists in world for more than 2^16 ticks (but actual bias will happen sooner
* because RNG is not sampled only once per tick, obviously)
*/
val Level.otmRandom: RandomSource get() = (this as IMatteryLevel).otmRandom ?: random