5 ms·

Shrinking a Kotlin Binary by 99.2%

100 points by farmerbb 6y ago

brabel 6y ago
If you're going to get rid of all your Kotlin std lib usages by explicitly replacing them, after inspecting the actual class files generated by the compiler, with standard Java methods (and hope that no future change will re-introduce them) and you care so much about the size of your jars, I would say you're better off simply going back to Java, perhaps using the very latest version (since you're willing to use Kotlin that shouldn't be a problem) which has lots of niceties and to me, at least, looks a lot better than using Kotlin with these kinds of hacks. Add a nullability static analysis check and you're gold.
- lmm 6y ago
  Disagree. A lot of the value of Kotlin is stuff that doesn't even make it into the binary, like scope functions.
- snafu109 6y ago
  The takeaway is "make sure you use a tool like R8 or ProGuard to remove unused code paths". That's where most of the savings came from, and the advice applies to Java projects as well. But true, if you care about every last byte, you might use Java instead. You might also use another language entirely.
- cglong 6y ago
  Haven't watched it yet, but looks like the author gave a talk recently about differences between Kotlin and the latest Java: https://jakewharton.com/whats-new-in-java-19-the-end-of-kotlin/ https://jakewharton.com/whats-new-in-java-19-the-end-of-kotl...
- dtech 6y ago
  At that point, why not use Rust or Go or D or whatever with significantly smaller binary sizes and (un-optimized) faster speeds.
  - saagarjha 6y ago
    Those compile to native.
  - tasubotadas 6y ago
    Not on Android
    - ChrisRR 6y ago
      C or C++ then
    - FlyingSnake 6y ago
      Rust has first class support for Android.
      - eptcyka 6y ago
        Cool, so I can start a new service and bind activities to it from Rust without having to deal with a nasty JNI or an unstable ABI that changes under my feet?
      - dgellow 6y ago
        What do you mean by "first class support" here? Some quick searches doesn't give me results that goes in this sense (nothing official from the rust and/or android projects).
      - untog 6y ago
        That's hardly the full story. Rust provides all the support it is able to provide for Android, yes. But it still relies on the NDK and has to sit behind a JNI layer. A "Kotlin vs Rust" comparison for Android is apples and oranges.
    - fnord123 6y ago
      On Android you are stuck with Java8 so GP's point melts away.
  - vips7L 6y ago
- MaxBarraclough 6y ago
  Doesn't it make more sense to look at this work as proof-of-concept for what the Kotlin compiler could do automatically?
- Jake_Wharton 6y ago
  The final section of the post was a Java port and size comparison. It also noted that while it was smaller, I simply don't want to use Java and the minute any external dependency is added (such as for CLI parsing) I'm right back to needing R8 for minifying. I removed that part since the post was long enough.
- edem 6y ago
  If you have used Kotlin you would have known that no sane person wants to go back to Java after being exposed to Kotlin.
  - brabel 6y ago
    What a silly way to look at things. If it matters, I've been programming more in Kotlin than in Java nowadays, and I have no trouble at all going back to Java... it's a nice language for its age and it gets the job done robustly. I even prefer Java for small applications that I want to distribute to users as small jars, for example. Kotlin has some nice benefits, but it's not a panacea that makes Java irrelevant - it actually strengthens the Java ecosystem in my opinion - it's another tool for the Java developer to use when appropriate.
wnoise 6y ago
> - val old = args[0].let(::File).readText() > - val new = args[1].let(::File).readText() > + val old = args[0].let(Paths::get).let(Paths::readString) > + val new = args[0].let(Paths::get).let(Paths::readString) Missed index. 0!=1.
- xvector 6y ago
  That’s an impressive catch. I would never have noticed this. How did you get this good at code review?
  - wnoise 6y ago
    Reading lots of code. And as the other commenter says, it's a bit easier when the correct code is right above it.
  - saagarjha 6y ago
    It helps that the correct code is just above the buggy replacement…
- burntcookie90 6y ago
  Fixed here: https://github.com/JakeWharton/jakewharton.com/commit/dbe1cfdefd870f12c4be3cc7d7f56368e189d869 https://github.com/JakeWharton/jakewharton.com/commit/dbe1cf...
toolslive 6y ago
It used to help a lot (30-40%) to sort the class files of a librarly on canonical name before you add them to its jar. Class files contain that name, and are (typically) small. Your compression factor will grow. (maybe that trick is standard now)
- Jake_Wharton 6y ago
  Removing `-dontobfuscate` will change all the package, type, and function names to be single letters for the same result of greater compression. The goal here was to just get it small enough, not the smallest it could possibly be.
setheron 6y ago
Looks like most of the size reduction was from running R8. The rest seems meaningless.
mro_name 6y ago
any idea how to get the swift upload network traffic down? My 500K objc ipa ported to swift http://mro.name/ShaarliOS http://mro.name/ShaarliOS now is ~8MB (OTA test ipa), ~28MB for production upload causing ~300MB traffic until finally uploaded via xcrun, taking 1h on my rural uplink. Has anybody an idea how to get back to sane dimensions?

100 points by farmerbb 6y ago

If you're going to get rid of all your Kotlin std lib usages by explicitly replacing them, after inspecting the actual class files generated by the compiler, with standard Java methods (and hope that no future change will re-introduce them) and you care so much about the size of your jars, I would say you're better off simply going back to Java, perhaps using the very latest version (since you're willing to use Kotlin that shouldn't be a problem) which has lots of niceties and to me, at least, looks a lot better than using Kotlin with these kinds of hacks. Add a nullability static analysis check and you're gold.

lmm 6y ago
Disagree. A lot of the value of Kotlin is stuff that doesn't even make it into the binary, like scope functions.
snafu109 6y ago
The takeaway is "make sure you use a tool like R8 or ProGuard to remove unused code paths". That's where most of the savings came from, and the advice applies to Java projects as well. But true, if you care about every last byte, you might use Java instead. You might also use another language entirely.
cglong 6y ago
Haven't watched it yet, but looks like the author gave a talk recently about differences between Kotlin and the latest Java: https://jakewharton.com/whats-new-in-java-19-the-end-of-kotlin/ https://jakewharton.com/whats-new-in-java-19-the-end-of-kotl...
dtech 6y ago
At that point, why not use Rust or Go or D or whatever with significantly smaller binary sizes and (un-optimized) faster speeds.
- saagarjha 6y ago
  Those compile to native.
- tasubotadas 6y ago
  Not on Android
  - ChrisRR 6y ago
    C or C++ then
  - FlyingSnake 6y ago
    Rust has first class support for Android.
    - eptcyka 6y ago
      Cool, so I can start a new service and bind activities to it from Rust without having to deal with a nasty JNI or an unstable ABI that changes under my feet?
    - dgellow 6y ago
      What do you mean by "first class support" here? Some quick searches doesn't give me results that goes in this sense (nothing official from the rust and/or android projects).
    - untog 6y ago
      That's hardly the full story. Rust provides all the support it is able to provide for Android, yes. But it still relies on the NDK and has to sit behind a JNI layer. A "Kotlin vs Rust" comparison for Android is apples and oranges.
  - fnord123 6y ago
    On Android you are stuck with Java8 so GP's point melts away.
- vips7L 6y ago
MaxBarraclough 6y ago
Doesn't it make more sense to look at this work as proof-of-concept for what the Kotlin compiler could do automatically?
Jake_Wharton 6y ago
The final section of the post was a Java port and size comparison. It also noted that while it was smaller, I simply don't want to use Java and the minute any external dependency is added (such as for CLI parsing) I'm right back to needing R8 for minifying. I removed that part since the post was long enough.
edem 6y ago
If you have used Kotlin you would have known that no sane person wants to go back to Java after being exposed to Kotlin.
- brabel 6y ago
  What a silly way to look at things. If it matters, I've been programming more in Kotlin than in Java nowadays, and I have no trouble at all going back to Java... it's a nice language for its age and it gets the job done robustly. I even prefer Java for small applications that I want to distribute to users as small jars, for example. Kotlin has some nice benefits, but it's not a panacea that makes Java irrelevant - it actually strengthens the Java ecosystem in my opinion - it's another tool for the Java developer to use when appropriate.

wnoise 6y ago

> - val old = args[0].let(::File).readText() > - val new = args[1].let(::File).readText() > + val old = args[0].let(Paths::get).let(Paths::readString) > + val new = args[0].let(Paths::get).let(Paths::readString) Missed index. 0!=1.

xvector 6y ago
That’s an impressive catch. I would never have noticed this. How did you get this good at code review?
- wnoise 6y ago
  Reading lots of code. And as the other commenter says, it's a bit easier when the correct code is right above it.
- saagarjha 6y ago
  It helps that the correct code is just above the buggy replacement…
burntcookie90 6y ago
Fixed here: https://github.com/JakeWharton/jakewharton.com/commit/dbe1cfdefd870f12c4be3cc7d7f56368e189d869 https://github.com/JakeWharton/jakewharton.com/commit/dbe1cf...

toolslive 6y ago

It used to help a lot (30-40%) to sort the class files of a librarly on canonical name before you add them to its jar. Class files contain that name, and are (typically) small. Your compression factor will grow. (maybe that trick is standard now)

Jake_Wharton 6y ago
Removing `-dontobfuscate` will change all the package, type, and function names to be single letters for the same result of greater compression. The goal here was to just get it small enough, not the smallest it could possibly be.

setheron 6y ago

Looks like most of the size reduction was from running R8. The rest seems meaningless.

mro_name 6y ago

any idea how to get the swift upload network traffic down? My 500K objc ipa ported to swift http://mro.name/ShaarliOS http://mro.name/ShaarliOS now is ~8MB (OTA test ipa), ~28MB for production upload causing ~300MB traffic until finally uploaded via xcrun, taking 1h on my rural uplink. Has anybody an idea how to get back to sane dimensions?