Tomek Kuźma mapedd

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

	enum AppState: Equatable {
	case featureOne(FeatureState)
	case featureTwo(FeatureState)
	case featureThree(FeatureState)
	}

	enum AppAction: Equatable {
	case featureOne(FeatureAction)
	case featureTwo(FeatureAction)
	case featureThree(FeatureAction)

	#import <Foundation/Foundation.h>
	#import <Cocoa/Cocoa.h>

	NSArray missingNumbers(NSArray a){
	if(a.count < 2){
	return [NSArray new];
	}

	NSMutableArray *array = [NSMutableArray new];
	for (NSInteger i = 0; i < a.count - 1; i ++) {

	//
	// LRUCache.m
	// ObjCAlg
	//
	// Created by Tomasz Kuzma on 20/02/2015.
	//



	#import <Foundation/Foundation.h>

	// Playground - noun: a place where people can play

	import Cocoa

	func eratosthenes(n: Int) -> [Int]{

	var results = Array(1...n)

	for i in 1...(n-1){
	var number = results[i]

	import Foundation


	func eratosthenes(n: Int) -> [Int]{

	var results = [Int]()

	for i in 0...(n-1){
	results.append(i+1)
	}

	#import <Foundation/Foundation.h>


	BOOL isDictionary(id object);
	BOOL isString(id object);
	BOOL isArray(id object);

	void addObjectForKeyToArray(NSString key, id collection, NSMutableArray array);
	void addArrayObjectsForKeyToArray(NSString searchKey, id collection, NSMutableArray array);

	#!/bin/bash
	#
	# (Above line comes out when placing in Xcode scheme)
	#
	# Inspired by original script by incanus:
	# https://gist.github.com/1186990
	#
	# Rewritten by martijnthe:
	# https://gist.github.com/1379127
	#

	#Gitignore for files generated by Xilinx ISE

	*.log
	*.svf
	*.scr
	*.cmd
	*.bak
	*.lso
	*.elf
	*.ace