ClojureScript and WebGL, trying to generate large javascript arrays (which is really slow)

[Andreas Arnold]

I'm trying to use ClojureScript to write a tile-based visualization with WebGL. This requires me to build up a large JavaScript array.

As you can see in the attached screenshot, this leads to a small problem: `clj->js` is really slow (this was run with a grid of 100x100).

Annotating the arrays with '#js' won't work since they are generated dynamically. Making the arrays offline is, as I see it, not an option either, since the colors of the tiles should change based on input, so one large JavaScript array at least is needed during the execution.

I was wondering if there is some other workaround for this? Or did I just stumble upon a use case where ClojureScript might not be a good solution?

[David Nolen]

You can construct JS arrays quickly just like you would in JavaScript.

David

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[Andreas Arnold]

You mean with `#js`? For example (def thing-one #js [1 2 3])? That way I can't use any ClojureScript methods like `map`, right?

A example might help to really figure out what I am trying to do here. I have code like the following:

(defn build-tile-vertices [x-coord y-coord]
(let [tile-template [[0 0 0]
[1 0 0]
[1 1 0]
[0 1 0]]
translate (fn [[x y z]] [(+ x x-coord) (+ y y-coord) z])]
(mapcat translate tile-template)))

Would there be a way to keep all of this directly as a JavaScript array? Or did you mean I should fall back to bare JavaScript? Or is there something totally different that I am missing?

[David Nolen]

If eeking out every last bit of performance is your #1 concern, then no you should not use ClojureScript functional operations over primitive arrays. loop/recur, aget, aset and standard Array methods are your friends.

David

[Andreas Arnold]

Thanks David!

I tried it today with `aset` and more 'basic' JavaScript and got it down to 50ms.

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[Yehonathan Sharvit]

You can also use amap and reduce to keep the functional spirit alive.

http://clojuredocs.org/clojure_core/clojure.core/amap
http://clojuredocs.org/clojure_core/clojure.core/areduce