10000 Short circuit type comparisons of type refs when eta-expansion is futile by retronym · Pull Request #5885 · scala/scala · GitHub
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Short circuit type comparisons of type refs when eta-expansion is futile #5885

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merged 1 commit into from
May 4, 2017
Merged

Short circuit type comparisons of type refs when eta-expansion is futile #5885

merged 1 commit into from
May 4, 2017

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retronym
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@retronym retronym commented May 4, 2017

If the initial comparison of a pair of higher kinded type refs yield false,
there is no point eta expanding them both to poly types to repeat the
comparison (in an more expensive fashion!)

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Short circuit type comparisons of type refs when eta-expansion is futile
989b22c 
If the initial comparison of a pair of higher kinded type refs yield false,
there is no point eta expanding them both to poly types to repeat the
comparison (in an more expensive fashion!)
@scala-jenkins scala-jenkins added this to the 2.12.3 milestone May 4, 2017
@retronym retronym requested a review from adriaanm May 4, 2017 00:02
@retronym retronym mentioned this pull request May 4, 2017
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retronym commented May 4, 2017 •
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Previous discussion in the context of #5823, from which I've split this PR:

#5823 (comment)

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retronym commented May 4, 2017 •
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Before:

% for sha in 2.12.3-bin-70fbf98-SNAPSHOT 2.12.3-bin-989b22c-SNAPSHOT;  do sbt "set scalaVersion in compilation := \"$sha\"" "hot -psource= -f3 -wi 10 -jvmArgs -Xmx1G"; sleep 10; done

[info] Benchmark                                   (extraArgs)  (source)    Mode  Cnt     Score   Error  Units
[info] HotScalacBenchmark.compile                                         sample  248  1259.374 ± 8.655  ms/op
[info] HotScalacBenchmark.compile:compile·p0.00                           sample       1226.834          ms/op
[info] HotScalacBenchmark.compile:compile·p0.50                           sample       1247.805          ms/op
[info] HotScalacBenchmark.compile:compile·p0.90                           sample       1286.393          ms/op
[info] HotScalacBenchmark.compile:compile·p0.95                           sample       1371.537          ms/op
[info] HotScalacBenchmark.compile:compile·p0.99                           sample       1425.287          ms/op
[info] HotScalacBenchmark.compile:compile·p0.999                          sample       1438.646          ms/op
[info] HotScalacBenchmark.compile:compile·p0.9999                         sample       1438.646          ms/op
[info] HotScalacBenchmark.compile:compile·p1.00                           sample       1438.646          ms/op

After:

[info] # Run complete. Total time: 00:10:50
[info]
[info] Benchmark                                   (extraArgs)  (source)    Mode  Cnt     Score   Error  Units
[info] HotScalacBenchmark.compile                                         sample  265  1235.682 ± 6.967  ms/op
[info] HotScalacBenchmark.compile:compile·p0.00                           sample       1203.765          ms/op
[info] HotScalacBenchmark.compile:compile·p0.50                           sample       1226.834          ms/op
[info] HotScalacBenchmark.compile:compile·p0.90                           sample       1265.422          ms/op
[info] HotScalacBenchmark.compile:compile·p0.95                           sample       1323.932          ms/op
[info] HotScalacBenchmark.compile:compile·p0.99                           sample       1366.672          ms/op
[info] HotScalacBenchmark.compile:compile·p0.999                          sample       1405.092          ms/op
[info] HotScalacBenchmark.compile:compile·p0.9999                         sample       1405.092          ms/op
[info] HotScalacBenchmark.compile:compile·p1.00                           sample       1405.092          ms/op

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adriaanm approved these changes May 4, 2017
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Nice! I like that the optimization is shared between sameType & subType.

@retronym retronym merged commit ce0e5b2 into scala:2.12.x May 4, 2017
@retronym retronym mentioned this pull request May 15, 2017
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@adriaanm adriaanm added the performance the need for speed. usually compiler performance, sometimes runtime performance. label May 25, 2017
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