in reply to Bidirectional lookup algorithm? (Updated: further info.)


Can you afford the memory footprint? If you have the RAM to spare, you should be getting O(1) lookups. On a Solaris box, I took your sample code and added another letter to get to most of 12 million entries for a memory footprint that was up in the 4 gigabyte class (3738M).

I'd expect that the hash implementation will be pretty time efficient compared to the alternatives, and it sounds like that's the main driver (assuming the RAM needs are not limiting).

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Re^2: Bidirectional lookup algorithm? (Updated: further info.)
by BrowserUk (Patriarch) on Jan 05, 2015 at 20:08 UTC

    The current hash lookups are very fast -- possibly as fast as I could hope to get -- the problem I'm trying to address is the memory consumed by the duplication of keys & values.

    As I said in the OP: "so the priority is the lookup speed -- preferably O(1) though O(logN) might be acceptable if the memory reduction was sufficient."

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