RIStAL Centre de Recherche en Informatique, Signal et Automatique - PowerPoint PPT Presentation

JNP : Symbolic WCET Computation Clément Ballabriga, Julien Forget, Giuseppe Lipari Real-Time System Symposium, Paris, December 2017 RIStAL Centre de Recherche en Informatique, Signal et Automatique de Lille 1

Parametric WCET Parametric Worst-case execution time (PWCET) produces a formula that represents the worst-case execution time of the program as a function of user-defined parameters Examples of parameters : Number of iterations in a loop depends on the size of a matrix Which alternative is taken in a if-then-else depends on an input variable The program uses an external library function, and the function WCET is still unknown 2

Our Method at a glance Control Flow Graph → Control Flow Tree → Formula Seq b 5 Loop ( b 1 ) b 1 b 1 Seq b 1 Alt b 3 w ( Loop ( b 2 )) = ( ⊤ , pack ( ⊤ , { 6 } , k ) ⊕ ( ⊤ , { 2 } )) b 2 b 4 b 6 b 6 Loop ( b 2 ) Seq b 2 b 5 b 3 b 2 b 4 Performance faster than ILP almost the same precision 3

What can you do with it ? Offline : Fast exploration of the space of parameters A component-based methodology Online : Adaptive systems ! The formula parameters are variable inputs We can instantiate the formula with the actual value of the input before executing the code, so to estimate its execution time Post-doc position available on this topic !! Looking forward to meet you at the poster !! 4