Axton Pitt axtonpitt

libdispatch efficiency tips

The libdispatch is one of the most misused API due to the way it was presented to us when it was introduced and for many years after that, and due to the confusing documentation and API. This page is a compilation of important things to know if you're going to use this library. Many references are available at the end of this document pointing to comments from Apple's very own libdispatch maintainer (Pierre Habouzit).

My take-aways are:

You should create very few, long-lived, well-defined queues. These queues should be seen as execution contexts in your program (gui, background work, ...) that benefit from executing in parallel. An important thing to note is that if these queues are all active at once, you will get as many threads running. In most apps, you probably do not need to create more than 3 or 4 queues.
Go serial first, and as you find performance bottle necks, measure why, and if concurrency helps, apply with care, always validating under system pressure. Reuse

	// An extension to replicate the same functionality from Vapor 3 with automatic content decoding:

	import Foundation
	import Vapor

	/// A basic, closure-based `Responder`.
	struct ContentBasicResponder<C: Content>: Responder {
	/// The stored responder closure.
	private let closure: (Request, C) throws -> EventLoopFuture<Response>

	import Vapor
	import Fluent

	// Example models
	final class Organization: Model, Content {
	static var schema = "organizations"

	@ID (key: .id)
	var id: UUID?

	/*
	* ------------------------------------------------------------
	* "THE BEERWARE LICENSE" (Revision 42):
	* github.com/xtenduke wrote this code. As long as you retain this
	* notice, you can do whatever you want with this stuff. If we
	* meet someday, and you think this stuff is worth it, you can
	* buy me a beer in return.
	* ------------------------------------------------------------
	*
	* This class is designed implement a 'similar' structure to TableView sections from iOS UIKit

	#!/bin/bash

	set -e

	CONTENTS=$(tesseract -c language_model_penalty_non_dict_word=0.8 --tessdata-dir /usr/local/share/tessdata/ "$1" stdout -l eng \| xml esc)

	hex=$((cat <<EOF
	<?xml version="1.0" encoding="UTF-8"?>
	<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
	<plist version="1.0">

	<application
	android:allowBackup="true"
	android:icon="@mipmap/ic_launcher"
	android:label="@string/app_name"
	android:roundIcon="@mipmap/ic_launcher_round"
	android:supportsRtl="true"
	android:theme="@style/AppTheme"
	android:networkSecurityConfig="@xml/network_security_config">

	/*
	* The MIT License
	*
	* Copyright (c) 2016 Andreas Ahlenstorf
	*
	* Permission is hereby granted, free of charge, to any person obtaining a copy
	* of this software and associated documentation files (the "Software"), to deal
	* in the Software without restriction, including without limitation the rights
	* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
	* copies of the Software, and to permit persons to whom the Software is

	let styles: [UIFont.TextStyle] = [
	// iOS 17
	.extraLargeTitle, .extraLargeTitle2,
	// iOS 11
	.largeTitle,
	// iOS 9
	.title1, .title2, .title3, .callout,
	// iOS 7
	.headline, .subheadline, .body, .footnote, .caption1, .caption2,
	]