2013-05-15 Threads. Why and how.

Transcript

1. Why we should use thread and how to do it with no additional efforts.
2.  Dominik Haska – Research Software Developer in Jeppesen a Boeing Company  9 years of professional programming including 1 year in IOS
3.  Why ◦ Moore law and physics limitations  How ◦ how to use the potentially power of multicore devices easily and properly
7.  iPhone 1 – 1 CPU 412 MHz  iPhone 5 – 2 CPU 1300 MHz  iPad 1 – 1 CPU 1000 MHz  iPad 4 (retina) – 2 CPU 1400 MHz
8.  all animations: ◦ GPU is a massive multiprocessor unit ◦ Just use the animation block [UIView animateWithDuration:1.0 animations:^{ firstView.alpha = 0.0; secondView.alpha = 1.0; }];
9. [UIView beginAnimations:@"ToggleViews" context:nil]; [UIView setAnimationDuration:1.0]; // Make the animatable changes. firstView.alpha = 0.0; secondView.alpha = 1.0; // Commit the changes and perform the animation. [UIView commitAnimations];
10.  Animation block stops user interaction during animation  animateWithDuration:delay: options: animations:completion:  UIViewAnimationOptions: ◦ UIViewAnimationOptionAllowUserInteraction ◦ UIViewAnimationOptionBeginFromCurrentState  [self.layer removeAllAnimations];
11.  CGRect animatedFrame = [self.animatedView.layer.presentationLayer frame];  CGRect targetFrame = self. animatedView.frame;  if(animatedFrame.origin.x != 0.0 || animatedFrame.origin.y != 0.0){ CGFloat xMis = animatedFrame.origin.x – targetFrame.origin.x; CGFloat yMis = animatedFrame.origin.y - targetFrame.origin.y; [fix the position]; }
12.  Create property with quee ◦ [NSOperationQueue new];  Create invocation ◦ NSInvocationOperation *operation = [[NSInvocationOperation alloc] initWithTarget:self selector:@selector(calculate) object:nil];  Add operation to quee ◦ [self.renderingQueue addOperation:operation];  Or remove (cancelAllOperations)
13.  Some code have to be executed in main thread ◦ [NSString sizeWithFont] – sometimes – once per 1-2 day crashes app ◦ [[UIView alloc] init] ◦ [view addSubview…]  Solution ◦ Delegate and perform on main thread performSelectorOnMainThread:@selector( ◦ Use NSAttributedString to work with UIKit Additions ◦ Always check when app crashes in which thread are you
14.  dispatch_async(dispatch_get_global_qu eue(DISPATCH_QUEUE_PRIORITY_DEFAULT), ^{ your code here }
15.  Long time for response  Multiple resources needed in parraler (webbrowsers)  Ready to use in ios:  [SSLConnection sendAsynchronousRequest:request queue:[NSOperationQueue mainQueue] completionHandler:^(NSURLResponse* response, NSData* data, NSError* error){ … }
16.  You have multicore devices – use this  Look for simplest solution – use library as much as possible  Focus on user interaction – do not freeze your apps  Be carefull with debugging – single thread app is much more testable – much much more  I work for jeppesen boeing company – if i show you sample code I have to kill you ;) – but next time I try to be better
17.  developer.apple.com  http://www.gotw.ca/publications/concurrenc y-ddj.htm - the free lunch is over  http://www.robotswillstealyourjob.com/ - robots are stealing your job – and engineers help them to  http://www.extremetech.com/computing/11 6561-the-death-of-cpu-scaling-from-one- core-to-many-and-why-were-still-stuck/2