progress bar code in vb net 2010 12: Monitoring, Analysis, and Performance Tools in Objective-C

Generation Data Matrix in Objective-C 12: Monitoring, Analysis, and Performance Tools

Listing 12 2. Fibonacci_FunAppDelegate.m -(IBAction)startCalculation:(id)sender { NSAutoreleasePool *fibPool = [[NSAutoreleasePool alloc] init]; NSString *outputString; outputString = @"1: "; for (int x=1; x < 11; x++) { long long int fibValues[90]; fibValues[0] = 0; fibValues[1] = 1; for (int i=2; i < 90; i++) { fibValues[i] = fibValues[i-2] + fibValues[i-1]; NSString *thisFibString; thisFibString = [[NSString alloc] initWithFormat:@"%lli, ",fibValues[i]]; outputString = [outputString stringByAppendingFormat:@"%@", thisFibString]; } outputString = [outputString stringByAppendingFormat:@"\n\n%i: ", x+1]; [outputField setStringValue:outputString]; } [fibPool drain]; }

OK, over to Interface Builder. Add a button to the window and connect it to the startCalculation: action of Fibonacci_FunAppDelegate. Also, add a multiline TextField and connect the outputField outlet of Fibonacci_FunAppDelegate to it. Add Autosizing parameters to enable the TextField to resize when you resize the window and keep the button at the bottom left (refer back to 3 if you need a refresher on this). Figure 12 1 shows what the interface should look like at this point.

Now go back to the Xcode Workspace and choose Build and Run. Click the button, and you should see something like Figure 12 2.

OK, we have a working application. Let s see how it looks in Instruments. You can actually run your application with Instruments from within Xcode (make sure that you build it first, though, using B this method just runs the currently built state of the application).

As you can see from Figure 12 3, there is a range of analysis tools available within Instruments. You are also able to run Shark from here you ll be learning more about Shark later in this chapter. For now, Choose the Run Run with Performance Tool Leaks menu item. You should see the Instruments window come up, together with the window for Fibonacci Fun. A timeline at the top of the window starts recording as soon as it loads, showing that it is monitoring your application. Click on the Leaks instrument at the top left, then position the Fibonacci Fun window so that you can see both. (See Figure 12 4.) Instruments is now monitoring for memory leaks.

We ll do a bit of orientation in a moment, but let s first get on with testing the application. You will see that the top timeline (monitoring object allocation) showed a couple of spikes when the application first loaded, then nothing more. The Leaks timeline is clean. Now click the Run calculation button in Fibonacci Fun and wait for a few seconds (the Leaks instrument samples every 10 seconds by default, though you can change that). Aha! What s this There is a red spike in the timeline and then blue lines. This is showing a memory leak. Click the button again, and you should see the same again. Leave the monitoring to run, and you should see a theme: clicking the button causes a memory leak, then nothing else until you click again. Click the record button at the top left of the Instruments window; the recording will stop and Fibonacci Fun will quit. The Instruments window will look something like Figure 12 5.

Now let s take a closer look at the report. The Instruments window is divided broadly into three sections: the list of instruments with their associated timelines, the Leaks Configuration pane, and the Leaked Object View. The Instruments list shows all of the instruments that you have chosen to use. You can add other instruments from the Library (you can see the Library using the button at the right-hand end of the toolbar). If you have run the Leaks instrument several times, you can see previous runs by clicking the disclosure arrow to the left of the icon in the Instruments list. The timeline shows the points at which Instruments has discovered memory leaks and indicates the total amount of leakage. The Leaks Configuration pane allows you to set a variety of parameters for your analysis. For example, you can choose the frequency of sampling or do an ad-hoc check at any point. The Leaked Object View shows the detailed report on the leakage. The default view (Leaked Objects Block View) is not terribly informative, showing the same leak every time (see Figure 12 6). It does indicate that the problem is something to do with a string, but there is not much more to tell than that.