How to decrease build times / speed up compile time in Xcode?

Question

What strategies can be used in general to decrease build times for any Xcode project? I\'m mostly interested in Xcode specific strategies.

I\'m doi

Answer 1

I switched to Hackintosh with a 5960x CPU, overclocked to 4.4GHz only to bring down Xcode compile time. That's 8 cores and 16 threads. Total cost $3000 for a computer that crushes all macs. However I've spent at least 10 days getting it set up, first with Yosemite, the. I had six months downtime when I couldn't update macOS while Xcode required a newer os. I just got it running sierra and life is good again.

My 2,8 GHz i7 double core 16 GB RAM MacBook Pro compiles my project in 75 seconds, the Hackintosh in 20 seconds. (Swift, dlib, opencv c++ in the project)

However the biggest problem is Xcode doesn't seem to use multiple threads when compiling swift. This is the bottleneck, I hope they will fix it soon.

Answer 2

Personally I switched compiler to LLVM-Clang for my Mac development projects and have seen a dramatic decrease in build times. There's also the LLVM-GCC compiler but I'm not sure this would help with build times, still that's something you can try too if LLVM-Clang does not work for iPhone app compilation.

I'm not 100% sure LLVM is supported for development on the iPhone but I think I remember reading in a news feed that it is. That's not an optimization you can implement in your code but it's worth the try!

Answer 3

Often, the largest thing you can do is to control your inclusion of header files.

Including "extra" header files in source code dramatically slows down the compilation. This also tends to increase the time required for dependency checking.

Also, using forward declaration instead of having headers include other headers can dramatically reduce the number of dependencies, and help all of your timings.

Answer 4

Easy answer: add another machine running Xcode on your local network. Xcode incorporates distcc to do distributed compiles. It can even use Bonjour to find other build hosts, which simplifies the process of configuring this greatly. For large builds, distributing can get you a speed increase that is nearly linearly proportional to the number of build machines (2 machines takes half the time, three takes a third and so on).

To see how to set this up, you can consult this development doc. It also features other useful build time improvement strategies, such as using precompiled headers and predictive builds.

Edit: Sadly, it appears Apple has removed this feature as of Xcode 4.3: http://lists.apple.com/archives/xcode-users/2012/Mar/msg00048.html

Xcode 5 has a server version which can do CI, but I doubt this will confer any benefit for ad hoc developer builds. However, there are some unannounced features that should dramatically speed up build times.

Answer 5

One huge tip to halve compile times (for iOS projects at least) is to set Build Settings / Architectures / Build Active Architecture Only to YES.

What this does (especially with the advent of 64-bit iPads/64-bit compiler) is to not build the binary for the architectures you're not currently using.

Make sure you remember to re-enable this setting on submission to the app store, or your binary will not validate.

Answer 6

Quick Note Regarding 'Throw more hardware at it' approach..

SUMMARY: I experienced a SMALL speed increase from making a SIGNIFICANT hardware upgrade

Test: Build/Run the exact same project on cloned macbooks (where the only difference should be their hardware)

Old Macbook Air (1.86GHZ Core 2 Duo ONLY 2GB RAM) vs Brand New Macbook Pro (2.3GHZ Core i7 8GB RAM)

BUILDING ON IPHONE 3GS
Macbook Air 1:00 - 1:15
Macbook Pro ~1:00

=> 0 to 0:15 of speed increase

BUILDING ON IPHONE 4S
Macbook Pro ~0:35
Macbook Air ~0:50

=> ~15 seconds of speed increase

**Partially tested: There DOES apear to a significant difference between build times for the SIMULATOR between the 2 machines

In my continued experience.. you WILL get a significant increase when making big changes in PHONE hardware (i.e. build time on a 3GS vs iphone 5 (or 4 for that matter)).. at least in my experience, the limiting factor was the phone hardware (not the computer hardware).

SO.. to get the fastest build time..
option1) write code and run in the simulater on a fast computer OR
option 2) build on the device with the lastest iphone