Marcel Weiher - iOS and macOS Performance Tuning: Cocoa, Cocoa Touch, Objective-C, and Swift

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Cocoa, Cocoa Touch, Objective-C, and Swift

Marcel Weiher

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ISBN-13: 978-0-321-84284-8
ISBN-10: 0-321-84284-7

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Marcel Weiher is a software engineer and researcher with more than 25 years of experience with Cocoa-related technologies. Marcels work has always been performance-focused, ranging from solving impossible pre-press problems on the machines of the day via optimizing one of the worlds busiest Web properties at the BBC to helping other Apple engineers improve the performance of their code on Apples Mac OS X performance team.

In addition to helping established companies and start-ups create award-winning software and turn around development teams, Marcel also teaches, blogs, speaks at conferences, contributes to open source, and invents new techniques such as Higher Order Messaging. He also works on programming languages, starting with an Objective-C implementation in 1987 and culminating in the Objective-Smalltalk architecture research language. Marcel currently works as a principal software engineer at Microsoft Berlin and maintains his own software and consulting company, metaobject ltd.

Performance is one of the most important qualities of software programs. You cant have world-beating software without world-beating performance. For a long time, hardware improvements meant that worrying about software performance seemed a waste of time, but with Moores Law no longer automatically providing significant automatic performance improvements, performance optimization is coming back to the forefront of both computer science and engineering.

In addition, performance for end users seems to have gotten only marginally better, whereas the performance of the underlying hardware has improved by many orders of magnitude. Bill Gates quipped that the speed of software halves every 18 months, whereas Wirths law in A Plea for Lean Software states, Software is getting slower more rapidly than hardware becomes faster.

We are so used to this sorry state of affairs that industry veterans were surprised at the original iPads fluid UI, despite having a CPU with only 1 GHz. Thats more than 1,000 times faster than my Apple ][, and 40 times faster than my NeXT cube that had a larger screen to deal with. If anything, the surprise should have been that it wasnt faster, especially when considering that it also had a GPU to handle the screen.

This book will try to give insights into the underlying reasons for these developments in the context of Objective-C, Cocoa, and CocoaTouch, and attempt to provide techniques for taking full advantage of the raw power of our amazing computing machinespower that we tend to squander with reckless abandon. It will also try to show when it is actually OK to squander that power, and when it is necessary to pay careful attention. Programmer attention is also a scarce resource, too often squandered attempting to optimize parts of the program that do not matter.

General themes will include latency versus bandwidth, and transactions costs (overhead) versus actual work done, themes that are universal and manifest themselves in different forms at every level of the hardware and software stack.

What you will notice is that due to the speed of our machines, any single operation is, in fact, always more than fast enough, so the crucial equation is itemscost. Most optimization is about reducing one or both of the parts of that formula, usually by breaking it up first.

One frequent method for reducing cost is to realize that cost is actually composed of two separate costs, cost1 and cost2, and only one of these needs to be applied to all items: