Two (possibly off base, but given your description . . .) ideas that come to mind:

Edit: tweaked; upon rereading I don't get that your dataset's necessarily sparse (in that you need to quickly check for membership or not) so the bloom suggestion's off base probably.

The cake is a lie.
The cake is a lie.
The cake is a lie.

In reply to Re^3: 32bit/64bit hash function: Use perls internal hash function? by Fletch
in thread 32bit/64bit hash function: Use perls internal hash function? by sectokia

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