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1. The Layer Tree

Core Animation's original name is Layer Kit

Core Animation is a compositing engine; its job is to compose different pieces of visual content on the screen, and to do so as fast as possible. The content in question is divided into individual layers stored in a hierarchy known as the layer tree. This tree forms the underpinning for all of UIKit, and for everything that you see on the screen in an iOS application.

In UIView, tasks such as rendering, layout and animation are all managed by a Core Animation class called CALayer. The only major feature of UIView that isn’t handled by CALayer is user interaction.

There are four hierarchies, each performing a different role:

Shared-nothing architecture

A shared-nothing architecture (SN) is a distributed-computing architecture in which each update request is satisfied by a single node (processor/memory/storage unit). The intent is to eliminate contention among nodes. Nodes do not share (independently access) memory or storage. One alternative architecture is shared everything, in which requests are satisfied by arbitrary combinations of nodes. This may introduce contention, as multiple nodes may seek to update the same data at the same time.

source: https://en.wikipedia.org/wiki/Shared-nothing_architecture

Reactive

An API for asynchronous programming with observables streams.

CPU load

source: https://stackoverflow.com/questions/9229333/how-to-get-overall-cpu-usage-e-g-57-on-linux

Take a look at cat /proc/stat

grep 'cpu ' /proc/stat | awk '{usage=($2+$4)*100/($2+$4+$5)} END {print usage "%"}'

EDIT please read comments before copy-paste this or using this for any serious work. This was not tested nor used, it's an idea for people who do not want to install a utility or for something that works in any distribution. Some people think you can "apt-get install" anything.

	#!/bin/bash

	rev="12"

	_log(){
	echo "$(date '+%Y-%m-%d %H:%M:%S') - ${streamid} - $1" >> /tmp/ffmpeg.log
	}

	_log_para(){
	echo "$1" \| fold -w 120 \| sed "s/^.*$/$(date '+%Y-%m-%d %H:%M:%S') - ${streamid} - = &/" >> /tmp/ffmpeg.log

	#!/bin/bash
	# You Will need to install iStats
	# gem install istats

	echo && echo ———————-System Information:——————— &&
	/bin/echo -n "Uptime: " && uptime \| awk '{print $3}'
	echo
	/bin/echo -n "CPU Usage: " && top -l 1 \| awk '/CPU usage/ {print $3}'
	/bin/echo -n "CPU Temp: " && istats \| grep CPU\ temp \| awk '{print $3}'
	/bin/echo -n "FAN Speed: " && istats \| grep Fan\ 0\ speed: \| awk '{print $4,$5}'

	extension String {
	var localized: String {
	return NSLocalizedString(self, comment: "")
	}
	}

	// Which allows for:
	"Hello world".localized

	import UIKit

	extension UIImage {

	// colorize image with given tint color
	// this is similar to Photoshop's "Color" layer blend mode
	// this is perfect for non-greyscale source images, and images that have both highlights and shadows that should be preserved
	// white will stay white and black will stay black as the lightness of the image is preserved
	func tint(tintColor: UIColor) -> UIImage {

	+ (NSDateFormatter *)dateReader
	{
	NSMutableDictionary *dictionary = [[NSThread currentThread] threadDictionary];
	NSDateFormatter *dateReader = [dictionary objectForKey:@"SCDateReader"];
	if (!dateReader)
	{
	dateReader = [[[NSDateFormatter alloc] init] autorelease];
	dateReader.locale = [[[NSLocale alloc] initWithLocaleIdentifier:@"en_US_POSIX"] autorelease];
	dateReader.timeZone = [NSTimeZone timeZoneForSecondsFromGMT:0];
	dateReader.dateFormat = @"EEE, dd MMM yyyy HH:mm:ss Z";

	#########################
	# .gitignore file for Xcode4 and Xcode5 Source projects
	#
	# Apple bugs, waiting for Apple to fix/respond:
	#
	# 15564624 - what does the xccheckout file in Xcode5 do? Where's the documentation?
	#
	# Version 2.1
	# For latest version, see: http://stackoverflow.com/questions/49478/git-ignore-file-for-xcode-projects
	#