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32	32
33	33	**getImage() / takePicture()**
34	34
	35	+**
	36	+**
	37	+
	38	+Note that we get no information, on how long those function calls might take. The alternative might be better or worse than the original.**
	39	+**
	40	+
35	35
36	36
37	37	Now we can start to swap host code calls in the textual code to revise our model:
...	...	@@ -38,4 +38,24 @@
38	38
39	39	[[image:attach:ExperimentExampleArrows.png]][[attach:ExperimentExampleArrows.png]]
40	40
41		-
	47	+Suppose we decide to exchange the call to getImage() with a call to takePicture(). Then we will find that the time values do not change at all:
	48	+
	49	+[[image:attach:Bildschirmfoto 2016-01-13 um 18.02.18.png]][[attach:Bildschirmfoto 2016-01-13 um 18.02.18.png]]
	50	+
	51	+[[image:attach:Example1.png]][[attach:Example1.png]]
	52	+
	53	+We can deduce that either getImage() and takePicture() take exactly the same amount of time (which is unlikely) or in worst case the transition with the second priority in HandleMotor is taken (accelerator not true). writeLog() is executed, but not takePicture() (and also not getImage() before). Therefore, exchanging getImage() for takePicture() does not show any effect.
	54	+
	55	+So let's change writeLog() to logProcess() then:
	56	+
	57	+[[image:attach:Example2.png]][[attach:Example2.png]]
	58	+
	59	+Now quite a lot has happened: First of all, we have reduced the overall worst case execution time. The decision to replace writeLog() with logProcess() seems to have been a good one. We are not done however, as we have to get below 500 tu. Second we can see that the worst case execution path has switchend and now HandleEmergency is the most time consuming region of the model. This means that errorLog() must take longer than either takePicture() or logProcess(). So now we exchange errorLog() for logErrors():
	60	+
	61	+[[image:attach:Example3.png]][[attach:Example3.png]]
	62	+
	63	+Now that was successful as well, as the overall worst case execution time is reduced again. Also, the worst case path has switched back to the HandleMotor region. That means that either logProcess() or TakePicture() take longer than logErrors(). As we already know we can only make logProcess() worse by exchanging it for writeLog(), we will now choose to change takePicture() back to getImage(). For, though we were not able to see the effect before, because writeLog() was even worse, we made a bad decision in the beginning by choosing takePicture() over getImage(). So let's revise this:
	64	+
	65	+[[image:attach:Example4.png]][[attach:Example4.png]]
	66	+
	67	+And now we have done it! The overall worst case execution time is finally below 500 and we are finished!

Confluence.Code.ConfluencePageClass[0]

Id

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1		-14516383
	1	+14516388

URL

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1		-https://rtsys.informatik.uni-kiel.de/confluence//wiki/spaces/KIELER/pages/14516383/Experiment Hotspot-Highlighting
	1	+https://rtsys.informatik.uni-kiel.de/confluence//wiki/spaces/KIELER/pages/14516388/Experiment Hotspot-Highlighting