Hi Sam;
I'm currently trying to get some functions written in clojure(-script)
running on Android, wrapping them in a java class generated by rhino.
Currently, I'm stuck at overcoming the 64k limit. Could you explain the
splitting process in some greater detail?
All the best,
Gerrit
PS ~ Any eta on Lambdroid?
Am Samstag, 22. November 2014 04:18:21 UTC+1 schrieb Sam Beran:
>
> The code is still half-baked, but in leu of a blog post or code, I can
> summarize my reasoning and approach:
>
>
> *ClojureScript is Designed With UI Responsiveness In Mind*
>
> At present, JVM Clojure is not currently suitable for Android development.
> Since Android applications are structured around ephemeral Activities,
> any startup penalty over 250 ms is simply unacceptable. Current benchmarks
> [1] are showing 2-5 seconds of startup time, and I have seen no
> straightforward advice on how to achieve an order-of-magnitude increase in
> startup performance. ClojureScript (and JavaScript) is designed from the
> ground up with startup speed in mind. ClojureScript can be used to create
> responsive user interfaces on Android.
>
>
> *Selecting a Host Runtime*
>
> In order to run ClojureScript on Android, I considered the following
> options for host runtimes:
>
> - *Android WebView * - we can achieve reasonable startup times with a
> WebView, however any data must be serialized and deserialized in order to
> communicate between a WebView and Java. Even worse, any long-running
> object
> lifecycles must be manually managed, since we cannot rely on garbage
> collection to maintain object references between the host VM and those of
> the WebView.
> - *V8 (JNI) - *I briefly considered compiling a V8 runtime to host
> ClojureScript. Startup speed would probably outperform the WebView. This
> would be a lot of work to develop a nice bridging mechanism. Object
> lifecycle management is better than WebView, but still not ideal. With no
> C++ or JNI background, I could tell very quickly that this would not be a
> "weekend project".
> - *Rhino* - Rhino is a lightweight JavaScript runtime for the JVM.
> Execution speed is not fast, and since Rhino is not actively maintained,
> it
> will probably never support ES6 - not huge concerns for ClojureScript.
> Since Rhino is a pure-Java runtime, there is very little overhead when
> communicating between JS<-> Java, and Java GC can be used to maintain
> object lifecycles.
> - *Nashorn *- the successor to rhino. Not an option until Android
> supports InvokeDynamic.[2]
>
>
>
> *Achieving Fast Startup on Rhino*
>
> When I initially ran ClojureScript on Rhino, Startup speed was around 8-10
> seconds - even worse than JVM Clojure! Some quick measurements indicated
> that the bulk of the time was spent with Rhino parsing the JS sources for
> cljs/core.js. I was pleased to discover that Rhino supports bytecode
> precompilation via the jsc utility [3]. I was able to precompile the
> ClojureScript output to bytecode, and achieve *much faster startup -
> around 150ms on device*. This is well within the target performance
> range, and is fast enough to eliminate any noticeable UI lag.
>
> One hurdle I ran into is the 64k method size limit for Java classes. Since
> jsc compiles all .js files to a single method in a Java class, compiling
> cljs/core.js caused errors when compiling to bytecode. I was able to get
> around this by splitting the JS files in half during the build process
> until they were small enough to compile. *I have since implemented some
> optimizations which bring the startup overhead of ClojureScript down to <
> 100 ms.*
>
>
> *Pure ClojureScript Android Applications*
>
> Since I am precompiling the ClojureScript sources, I can also generate
> Java classes using ClojureScript macros. Here is an example of an Android
> Activity written in ClojureScript. This activity is compiled to Java in a
> similar manner to Clojure's gen-class mechanism:
>
> (ns cljs-hello.core
> (:require-macros [lambdroid.compile :refer [java-class]]))
>
> (java-class
> {:name "io.lambdroid.MyActivity"
> :extends android.app.Activity})
>
> (defn ^:override onCreate [this ^android.os.Bundle state]
> (.onCreate this state)
> (.setContentView this io.lambdroid.R.layout/activity_hello_world)
> (.setText (.findViewById this io.lambdroid.R.id/message
> <http://io.lambdroid.r.id/message>)
> "Hello From ClojureScript"))
>
>
> Note that this generated activity class is created by Android directly and
> has full access to Android asset bundles, so users of this library *will
> not need to write any Java whatsoever* .
>
>
> *Next Steps*
>
> There are a few things I still need to do before releasing code:
>
>
> - Extract build logic into Gradle plugin - it is currently just some
> build scripts in an example app.
> - Build an Android REPL that can run in the context of the current
> activity
> - Incremental builds (cljs compile time is currently slow)
>
>
> Once these are finished, I plan to release Lambdroid under a permissive
> license.
>
>
> *ClojureScript JVM Applications?*
>
> As Uday and Mike have alluded, this appriach could potentially be used to
> run applications on the JVM as well. This would be ideal for CLI
> applications and development. However, due to the many differences between
> CLJS and Clojure[4], I think this might be difficult to write the necessary
> shims to get something like Leiningen running on Clojurescript. Also, I
> think Nashorn would be a more suitable runtime for JVM applications. I’d
> love to have someone with more experience weigh in on this possibility!
>
> Cheers,
> Sam
>
> [1]
> http://nicholaskariniemi.github.io/2014/03/12/clojure-android-startup-benchmarks.html
> [2]
> http://mail.openjdk.java.net/pipermail/nashorn-dev/2013-January/000240.html
> [3]
> https://developer.mozilla.org/en-US/docs/Mozilla/Projects/Rhino/JavaScript_Compiler
> [4] https://github.com/clojure/clojurescript/wiki/Differences-from-Clojure
>
>
>
--
You received this message because you are subscribed to the Google
Groups "Clojure" group.
To post to this group, send email to [email protected]
Note that posts from new members are moderated - please be patient with your
first post.
To unsubscribe from this group, send email to
[email protected]
For more options, visit this group at
http://groups.google.com/group/clojure?hl=en
---
You received this message because you are subscribed to the Google Groups
"Clojure" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to [email protected].
For more options, visit https://groups.google.com/d/optout.
