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On Thu, 07 Jun 2018 19:02:42 +1200, Gregory Ewing wrote: > Steven D'Aprano wrote: >> But if it were (let's say) 1 ULP greater or less >> than one half, would we even know? > > In practice it's probably somewhat bigger than 1 ULP. > A typical PRNG will first generate a 32-bit integer and > then map it to a float, giving a resolution coarser than > the 52 bits of an IEEE double. > > But even then, the probability of getting exactly 0.5 > is only 1/2^32, which you're not likely to notice. But gosh, if there are only 2**32 different "random" floats, then you'd have about a 50% chance of finding a collision among any set of 2**16 samples. Is that really tolerable?

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