Very long compile time in large functions

[samuelbeek]

Hi, using this tool, I found that a some of the larger constrain functions in my app take a really long time to compile, in the 500ms spectrum on a pretty new MacBook Pro. Do you know if there's specific things that cause these longer compile times? I'd love to contribute some improvements and can do some tests myself, but if you happen to know where to look that'd be great.

Thanks

[MPiccinato]

Just wanted to chime in and say I am seeing this also. Currently a huge chunk of my build time is spent in these methods. I use the same tool as @samuelbeek posted.

[samuelbeek]

Both @MPiccinato and I dove into this and it is slowest when combining assignment and comparison operators. So for instance in a line like this one
view1.centerX == view.centerX + 10.

Anything we can do about that?

[samuelbeek]

I've added a couple of functions to my project to replace the == operator in cartography. You can find them in this Gist (WIP). It slimmed down the compile time of most Cartography blocks to 30% of the original time, which are pretty impressive results.

[LucasVanDongen]

I'm seeing the same things. Compile times over 100ms for not overly complex stuff

Noticed one thing:

    constrain(self.contentView, self.titleLabel, self.contentLabel, self.newMessages) { (view: LayoutProxy, titleLabel: LayoutProxy, contentLabel: LayoutProxy, newMessages: LayoutProxy) in
        titleLabel.bottom == contentLabel.top
        
        titleRight = titleLabel.right == view.right - (intraCellSpacing + MessageCountIndicator.counterWidth) // Much faster
        contentLabel.right == titleLabel.right
        
        newMessages.centerY == view.centerY
        newMessages.right == view.right - intraCellSpacing
        newMessages.width == newMesagesWidth
        
        contentLabel.bottom == view.bottom - intraCellSpacing
        contentLabel.left == titleLabel.left
    }

vs

    constrain(self.contentView, self.titleLabel, self.contentLabel, self.newMessages) { (view: LayoutProxy, titleLabel: LayoutProxy, contentLabel: LayoutProxy, newMessages: LayoutProxy) in
        titleLabel.bottom == contentLabel.top
        
        titleRight = titleLabel.right == view.right - intraCellSpacing - MessageCountIndicator.counterWidth  // Slow version
        contentLabel.right == titleLabel.right
        
        newMessages.centerY == view.centerY
        newMessages.right == view.right - intraCellSpacing
        newMessages.width == newMesagesWidth
        
        contentLabel.bottom == view.bottom - intraCellSpacing
        contentLabel.left == titleLabel.left
    }

This shaved off 200ms from originally >300ms. Still not really great having them over 100ms but at lot better at least.

[CVertex]

Is it to do with type inference? Swift is still a dog with that

[Lascorbe]

I've come into this as well (having big compile times on all Cartography closures).

Looks like function overload could be the cause (constrain has various method overloads). I've been thinking how can we change it to solve the problem, but it is so good like it is right now...

Does someone think there's a good way of fixing it? Or should we just keep relying on thinking it'll get better on a future Xcode release?
I've thought of just having the constrain(_ view: [View] ...) one, and rename the other ones so it's clear which one is used, but I don't really like it :(

[ianyh]

I'm not sure it's the constrain overloads. I've tried reducing it to only the array call with no meaningful difference in compile time.

[ianyh]

For what it's worth, anecdotally this seems to be a lot faster for me nowadays.

[rvi]

@ianyh What did you change to reduce the compile time?

[ianyh]

Nothing. Swift compiler changes seem to have improved the type inference, which is what I think was slowing it down.

[ianyh]

Again, this is somewhat anecdotal. I haven't done any thorough timing tests.

[rvi]

Building my app after cleaning is more than 11min... Xcode 8.3.2 ?

[ianyh]

Yes. It's possible I've just adjusted to my capricious robot overlords. I'll do some more thorough timing when I get a chance.

[pedromcunha]

Any update on this issue? We have some large (30 line) constrain functions that are giving us 600-700ms compile time. Is there anything we can do to decrease this? Btw it looks like it hasn't been mentioned before but you can measure the compile time of functions by following this guide here: https://www.jessesquires.com/blog/measuring-compile-times-xcode9/?utm_campaign=iOS%2BDev%2BWeekly&utm_medium=web&utm_source=iOS_Dev_Weekly_Issue_320

[orta]

No updates, so you're welcome to take a look 👍