alt Hacker NewsMy best improvment was just bit-interleaving both axes of a 2x32bit integer coordinate (aka z-curve). I obtained factor ~100x (yes factor not percent) throughput improvement over locality in only one dimension. All it took was ~10 lines of bit twiddling. The runtime went from a bit above 300ms to slightly less then 3ms.
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throw-the-towel • yesterday at 10:44 PM
I'm wondering how do you folk even come up with this kind of optimisations.
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End to end gets weird. I was asked to look at an admin page, nobody could figure out why it was 30s. Literally the first thing I tried got it under 4 and the second down to three. It was pulling the same list of rows twice, applying two filters and then looking at the intersection. I changed the signature to send the list as input instead of the query constraints. Then I changed them to avoid the intersect.
If you would have asked me to bet on which one would have had the bigger impact I would have split the difference.
My second favorite was similar. Two functions making a call instead of sharing the answer. Profiler said 10% cumulative. I removed half. Instead of 5% I got 20%. Which just demonstrates how much data a profiler cannot show you.