pwcet: a tool for probabilistic worst-case execution time analysis of real-time systems. Traditional approaches for worst case execution time (WCET) analysis aim at finding the absolute upper bound on the execution time. For modern high performance processors with, for example, out-of-order execution, these technique may produce estimates for the WCET which are pessimistic due to the simplifications that may need to be made and due to the inherent variability of the execution time. In addition, end to end measurements as used in industry produce estimates of the execution time that potentially underestimate the real worst case execution time. We introduce the notion of probabilistic hard real-time system as a system which has to meet all the deadlines but for which a (high) probabilistic guarantee suffices. pWCET combines both measurement and analytical approaches into a model for computing probabilistically bounds on the execution time of the worst case path of sections of code. The technique behind pWCET is based on combining (probabilistically) the worst case effects seen in individual blocks to build the execution time model of the worst case path of the program (such case may have not been observed in the measurements).