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Commit2a73164

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Improve set of candidate multipliers for perfect hash function generation
The previous set of multipliers was not adapted for large sets of shortkeys, and this new set of multipliers allows to generate perfect hashfunctions for larger sets without having an impact for existing callersof those functions, as experimentation has showed. A future commit willmake use of that to improve the performance of unicode normalization.All multipliers compile to shift-and-add instructions on most platforms.This has been tested as far back as gcc 4.1 and clang 3.8.Author: John NaylorReviewed-by: Mark Dilger, Michael PaquierDiscussion:https://postgr.es/m/CACPNZCt4fbJ0_bGrN5QPt34N4whv=mszM0LMVQdoa2rC9UMRXA@mail.gmail.com
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‎src/tools/PerfectHash.pm

Lines changed: 2 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -81,13 +81,13 @@ sub generate_hash_function
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# to calculate via shift-and-add, so don't change them without care.
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# (Commonly, random seeds are tried, but we want reproducible results
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# from this program so we don't do that.)
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my$hash_mult1 =31;
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my$hash_mult1 =257;
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my$hash_mult2;
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my$hash_seed1;
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my$hash_seed2;
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my@subresult;
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FIND_PARAMS:
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foreach (127, 257, 521, 1033, 2053)
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foreach (17, 31, 127, 8191)
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{
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$hash_mult2 =$_;# "foreach $hash_mult2" doesn't work
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for ($hash_seed1 = 0;$hash_seed1 < 10;$hash_seed1++)

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