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Comment by bajsejohannes | Hacker News Reader

One thing I don't understand from watching the video, is what happens in the (very rare) case that you get collisions all the way down the funnel. I assume this is related to the "One special final level to catch a few keys" (around 14:41 in the video), but given that it has to be fixed size, this can also get full. What do you do in that case?

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The dereference table allows allocations to fail:

https://arxiv.org/pdf/2501.02305#:~:text=If%20both%20buckets...

(the text fragment doesn't seem to work in a PDF, it's the 12th page, first paragraph)

Thanks! So I guess the best recourse then is to resize the table? Seems like it should be part of the analysis, even if it's low probability of it happening. I haven't read the paper, though, so no strong opinion here...

(By the way, the text fragment does works somewhat in Firefox. Not on the first load, but if load it, then focus the URL field and press enter)

This bothered me too, reading it and the sample implementations I've found so far just bail out. I thought one of the benefits of hash tables was that they don't have a predefined size?

The hash tables a programmer interacts with generally very much have a fixed size, but resize on demand. The idea of a fixed size is very much a part of the open addressing style hash tables -- how else could they even talk of how full a hash table is?

Yeah, I presume so. At least that's what Swiss Tables do. The paper is focused more on the asymptotics rather than the real-world hardware performance, so I can see why they chose not to handle such edge cases

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