Rewrite double hashing algo again, to fix cycle of length size issue #7
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Release v2.0.0
Enhanced double hashing stops cycles of length less than `size` in the case where size is coprime with the second hash. But you still get cycles of length `size`. So if we reach there and haven't finished, append a prime to the input and rehash. Also fix poorly implemented cubic term: interpreted (n^3 - n)/6 mod m wrongly (division should have been mult inverse under mod m, not integer floor division). Reimplemented correctly.
kblauhut
requested changes
Dec 13, 2021
Yes - sorry, I'd done that on my main branch but not on the xxh version, now done |
kblauhut
approved these changes
Dec 13, 2021
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Enhanced double hashing stops cycles of length less than
sizein the case where size is coprime with the second hash. But you still get cycles of lengthsize. So if we reach there and haven't finished, append a prime to the input and rehash.Also fix poorly implemented cubic term: interpreted (n^3 - n)/6 mod m wrongly (division should have been mult inverse under mod m, not integer floor division). Reimplemented correctly.
I think this should now be both efficient and resilient against pathological inputs.