Why is Swift so slow (timeout) in compiling this code?

Using Swift
21

Also, using mmap means... well, that you need mmap.

That takes you out of the domain of pure-Swift code and introduces an OS dependency. Now you need to do this whole dance to make your code portable:

#if canImport(Darwin)
  import Darwin
#elseif canImport(Glibc)
  import Glibc
#elseif canImport(WasiLibc)
  ... etc

Also, Windows apparently doesn't have mmap, but has a similar function called MapViewOfFile. So you'll need to deal with that, too.

Alternatively, that static data could just live in the binary, and you could just access it like a regular Swift array without bothering with any of this.

Of course, there are other considerations which might cause you to want to split the data as a separate file which you load at runtime. Compile time shouldn't be one of those considerations, IMO.

4 Likes
22

My results on Intel MacBook, Xcode 14.1

% time swiftc -o app big_qs.swift
swiftc -o app big_qs.swift  38.93s user 3.43s system 98% cpu 42.823 total

And if patched with

- let vector = [
+ let vector = [Int](arrayLiteral:

% time swiftc -o app fix_qs.swift
swiftc -o app fix_qs.swift  14.71s user 6.61s system 98% cpu 21.629 total

% swiftc -version
swift-driver version: 1.62.15 Apple Swift version 5.7.1 (swiftlang-5.7.1.135.3 clang-1400.0.29.51)
Target: x86_64-apple-macosx12.0

Adding optimizations:

% time swiftc -O -o app big_qs.swift
swiftc -O -o app big_qs.swift  188.67s user 5.51s system 99% cpu 3:15.38 total
% time swiftc -O -o app fix_qs.swift
swiftc -O -o app fix_qs.swift  15.77s user 6.09s system 99% cpu 21.967 total
2 Likes
23

Thanks for testing out. Surprising that it looks to work on Intel but not on my M1. The first one still fails; and the second one does work but the output shows that only 16959 numbers were taken into consideration.

time swift run
Building for debugging...
[3/3] Linking swiftqs
Build complete! (31.30s)
16959 16959
swift run  0.09s user 0.02s system 0% cpu 31.635 total

It seems this is pretty much the only way that works very well taking all the 999999 numbers into consideration.

swift run
Building for debugging...
[3/3] Linking swiftqs
Build complete! (0.58s)
999999 999999
3 Likes
24

Uh, nice catch. It is the same for me.

1 Like