Swift Performance: Too Slow for Production

I find posts like this nearly entirely lacking in interest. There was so much attitude and not near enough actual analysis. A much stronger post would have actually disassembled the resulting code in each of the different configurations, and looked to see why the various permutations had the performance that they did. We would then have a much stronger understanding of where Swift's performance is at, instead of looking at a series of not exactly equivalent benchmarks that leave us wondering if we're not just seeing an artifact of the differences in the benchmark code as opposed to differences in real-world performance.

I for one would not be changing my approach based on this post. I might start doing some disassembly if I was writing performance sensitive production code in Swift, but that would be about it.

I also encounter binary size issue like 10 times bigger than the same program in ObjC!

I hacked together a quick reproduction of this since the author didn't provide any working code. I don't really know Swift and my Objective-C skills are pretty rusty at the moment, but it compiles and show similar performance characteristics: https://github.com/mnem/swift-json-speedtests

The initial Swift version the author created uses a third party library for wrapping the JSON decoding and that library appears to create a metric shit ton (technical term) of short lived objects whilst performing its magic. I cobbled together a less memory insane version (likely similar to the one described as Obj-C in Swift - although I disagree with that description) which is an order of magnitude faster. Finally there is an Objective-C version which is an order of magnitude faster again. All tests were running on an iPhone 5s in release mode.

Decoding JSON is an annoying task for most languages. That Swift decodes half a megabyte of JSON in a tenth of a second is a reasonable trade off, for me, when comparing it to the verbosity and occasional fiddlyness of working with Obj-C. It was quite nice to see how simple it was to mix Swift and Obj-C as I was creating this, so that suggests little downside to using Swift for the mundane tasks and coding specific bits in Obj-C when that's necessary for speed reasons - although Obj-C is not uniformly faster than Swift as noted in other articles.

Too Slow for Production _for now_.

Swift hasn't even been out for a year. Look at the progress it made since summer, it sped up a lot in certain parts.

Just file a radar on what's slow and they'll fix it.

Apple intentionally is shipping Swift as is to get devs ready and start planning for the next five years.