Improve dictionary compression speed #4170
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not as good as small-blocks improvement, but generally positive.
terrelln
approved these changes
Oct 16, 2024
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This patch generally improves dictionary compression speed for the
faststrategy, aka levels 1 & 2, following a method similar to #4165 .The gains are not uniform, and depend on the shape of the data. Tested on a set of various scenarios, one can observe speed gains as large as +14%, and as low as -2%, with the majority being around +5%. Therefore, this change is mostly positive, and when it's not, it's just by a small amount.
I also tried the same modification for
dfaststrategy, aka levels 3 & 4, but did not observe similar speed gains. That being said, during the investigation process, a few minor modifications were made to thedfastdictionary compression code, leading generally to slightly better compression ratios, by favoring longer matches over short ones.