[Performance Enhancements] Lambda expressions format change & Multi-level exploration logic changes#1535
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bulldozer-bot[bot] merged 14 commits intodevelopfrom Feb 23, 2026
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[Performance Enhancements] Lambda expressions format change & Multi-level exploration logic changes#1535bulldozer-bot[bot] merged 14 commits intodevelopfrom
bulldozer-bot[bot] merged 14 commits intodevelopfrom
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Before this PR
Some repos would take 5 - 9 mins to be formatted. This is because we were exploring both
preferBreakingLastInnerLevel&breakNormallyfor each level, with the branching coefficient capped to 20. The exploration is exponential. See below the Benchmark for the before implementation:After this PR
Performance dashboards here. Internal excavator runs here
Example of the new diff: here or here
Most of the times we prefer
preferBreakingLastInnerLevelin order to keep as compact as possible. I changed the logic that started the exploration top-down (with a branching coefficient capped at 20) to an exploration of the lastLAST_LEVELS_TO_EXPLORElevels. For the lastLAST_LEVELS_TO_EXPLOREI am exploring bothpreferBreakingLastInnerLevel&breakNormallyand I will pick the formatted text that minimises the number of lines.In order to keep the formatting as compact as possible, I am defaulting to
preferBreakingLastInnerLevelfor all the upper levels. If no such formatting was found, then I am falling back tobreakNormally.with
LAST_LEVELS_TO_EXPLORE=8Because the number of exploration is substantially decreased, just changing the above setup would end up in some cases looking like here. I've noticed that most of the time the setup was wrong was for lambda expressions.
I changed the logic for lambda expressions (lambda body with no curly braces), to instead of trying to inline as much as possible the inner levels of the lambda body (code here) to defaulting to
breakNormally:lambda expressionfits completely on the same line as the parent, it will be inlinedlambda bodygets split in multiple lines.Other things that I tried:
LAST_LEVELS_TO_EXPLORE = 12, noticed some perf regression for some repos.==COMMIT_MSG==
Improve perf by inspecting both breaking & not-breaking for the
LAST_LEVELS_TO_EXPLORElevels==COMMIT_MSG==
LAST_LEVELS_TO_EXPLORE = 7, however the formatting would regress in some cases (internal link here). Setting level = 12 fixed the issue.fj.Setto using a normalHashSet, however this ended up being (more than 10x) slower. This is because the State is immutable and every time we create a new State, we need to copy & edit eachSetfield, which is much more optimal to do with thefjlibrary than using a normalHashSet.See image below from the jfr.
Possible downsides?