Crash when `WeightedPicker#search` called with argument out of expected range

The following error crashed my server several times while generating terrain for minecraft:the_end with Chunky

java.util.concurrent.CompletionException: java.lang.IllegalArgumentException: The provided target value for entry selection must be less than or equal to the weight total
	at java.base/java.util.concurrent.CompletableFuture.encodeThrowable(CompletableFuture.java:315)
	at java.base/java.util.concurrent.CompletableFuture.completeThrowable(CompletableFuture.java:320)
	at java.base/java.util.concurrent.CompletableFuture$AsyncSupply.run(CompletableFuture.java:1770)
	at java.base/java.util.concurrent.CompletableFuture$AsyncSupply.exec(CompletableFuture.java:1760)
	at java.base/java.util.concurrent.ForkJoinTask.doExec(ForkJoinTask.java:373)
	at java.base/java.util.concurrent.ForkJoinPool$WorkQueue.topLevelExec(ForkJoinPool.java:1182)
	at java.base/java.util.concurrent.ForkJoinPool.scan(ForkJoinPool.java:1655)
	at java.base/java.util.concurrent.ForkJoinPool.runWorker(ForkJoinPool.java:1622)
	at java.base/java.util.concurrent.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:165)
Caused by: java.lang.IllegalArgumentException: The provided target value for entry selection must be less than or equal to the weight total
	at com.google.common.base.Preconditions.checkArgument(Preconditions.java:145)
	at net.fabricmc.fabric.impl.biome.WeightedPicker.search(WeightedPicker.java:79)
	at net.fabricmc.fabric.impl.biome.WeightedPicker.pickFromNoise(WeightedPicker.java:56)
	at net.fabricmc.fabric.impl.biome.TheEndBiomeData$Overrides.pick(TheEndBiomeData.java:132)
	at net.minecraft.class_2169.handler$zzc000$getWeightedEndBiome(class_2169.java:546)
	at net.minecraft.class_2169.method_38109(class_2169.java:82)
	at net.minecraft.class_2826.method_38291(class_2826.java:200)
	at net.minecraft.class_2791.method_38257(class_2791.java:393)
	at net.minecraft.class_3754.method_38327(class_3754.java:134)
	at net.minecraft.class_3754.method_38333(class_3754.java:124)
	at java.base/java.util.concurrent.CompletableFuture$AsyncSupply.run(CompletableFuture.java:1768)
	... 6 more

A full crash report is available here

Is this an issue with the Fabric API, as it appears?

[apple502j]

It seems like some versions of perlin noise can in fact produce values >= 1: see https://www.gamedev.net/forums/topic/285533-2d-perlin-noise-gradient-noise-range--/

[mwheeler]

Finished work, was able to download/build fabric and run this through a debugger to inspect the target value & find a more reliable repro location.

New tp command: /execute in minecraft:the_end run tp @a -1312 64 -800 (should crash even w/ low chunk radius / should be in that chunk - I’ve updated my previous comment):

-- Chunk to be generated --
Details:
	Location: -82,-50
	Position hash: -210453397586
	Generator: net.minecraft.world.gen.chunk.NoiseChunkGenerator@5cba22c

The target variable in this case is 1.0002144374246198 in my repro case… guessing it’s an issue w/ MC’s perlin noise implementation (probably some sort of error accumulation resulting in a tiny bit of overflow that causes results not to strictly be in the [0.0, 1.0] range all of the time).

Seems not too uncommon in some seeds? (I’ve found multiple places this crashes in my seed) - so I’d say it’s a serious bug (definitely has stopped me from being able to play my world this weekend unless I fudge my own local build of fabric-api to add an allowed bias over 1.0)