[GitHub] [arrow] westonpace commented on pull request #13487: ARROW-16945: [C++] Add new scalar compute function for 32-bit hashing

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westonpace commented on PR #13487:
URL: https://github.com/apache/arrow/pull/13487#issuecomment-1171714784

   > I'm not sure how to validate the hash outputs are "as expected". Further, unit tests for the hashing functions don't seem to validate hash outputs.
   
   For a hashing function I would expect:
    * If two values are equal then their hashes are equal
    * Given a random selection of non-equal values there should be some kind of expected false positive rate (e.g. equal hashes on unequal values).  Ideally we would include, as part of this, a benchmark that measures the FPR on random values.  You could then take then, pick a safe threshold (e.g. if the benchmark tends to show a 5% FPR then pick 10%) and put that into the unit test (e.g. assert the FPR is less than the safe threshold).


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