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Editorial Team
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Asked: 2026-06-15T20:01:43+00:00

I have two strings that are hashed into a ulong (using Google’s CityHash) during

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I have two strings that are hashed into a ulong (using Google’s CityHash) during separate processing stages and now must combine the two hashes into a new hash without significantly increasing the risk of a hash collision.

I know that XOR has some issues (such as Value ^ 0 = Value), but given that the two input values should already be well distributed, I suspect that I can combine the hashes like

ulong hash = hash1 ^ hash2; // hash1 and hash2 are ulong hashes of strings

Is there something wrong in this approach, or is there a better approach that does not add significant computational overhead?

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1 Answer

  1. Editorial Team

    Based on @GregS’s comments and my own further reading, I believe I’m not seriously degrading the hash distribution by using a simple XOR.

    That is the approach that seems wisest.

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