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> The real issue is that there were two values where one is much larger than another, and they were combined into a single variable without further consideration.

What do you mean by this? How is this related to the Far Lands generation?

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Graphical glitches I mentioned are independent from the Far Lands---AFAIK they start to happen around 1--2 million blocks from the origin, much closer than the Far Lands (~12.5 million blocks). The Far Lands itself is a result of noise generator bug with very large inputs [1].

[1] https://minecraft.wiki/w/Far_Lands#What_the_Far_Lands_are_no...

It's called catastrophic cancellation. Consider the following example:

999999 + 0.0000001 ~= 999999

Why doesn't it wrap around?

The problem is that there aren’t enough digits of precision to represent the answer. The exact answer would be 999999.0000001, but let’s say you only have space to store six significant digits. The exact answer is way more precise, so you need to round it to the nearest representable value, 999999.

Floating-point rounding issues are the same thing but with binary digits instead of decimal ones.

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