Combining Monitoring with Run-Time Assertion Checking

According to a study in 2002 commissioned by a US Department, software bugs annually costs the US economy an estimated $59 billion. A more recent study in 2013 by Cambridge University estimated that the global cost has risen to$312 billion globally. There exists various ways to prevent, isolate and fix software bugs, ranging from lightweight methods that are (semi)-automatic, to heavyweight methods that require significant user interaction. Our own method described in this tutorial is based on automated run-time checking of a combination of protocol- and data-oriented properties of object-oriented programs

Fixing the Sorting Algorithm for Android, Java and Python

Tim Peters developed the Timsort hybrid sorting algorithm in 2002. TimSort was first developed for Python, a popular programming language, but later ported to Java (where it appears as java.util.Collections.sort and java.util.Arrays.sort). TimSort is today used as the default sorting algorithm in Java, in Android (a widely used platform by Google for mobile devices), in Python and many other programming languages and frameworks. Given the popularity of these platforms this means that the number of computers, cloud services and mobile phones that use TimSort for sorting is well into the billions. After we had successfully verified Counting and Radix sort implementations in Java [1] with a formal verification tool called KeY, we were looking for a new challenge. TimSort seemed to fit the bill, as it is rather complex and widely used. Unfortunately, we weren’t able to prove its correctness. A closer analysis showed that this was, quite simply, because

Run-Time Verification of Black-Box Components Using Behavioral Specifications: An Experience Report on Tool Development

We introduce a generic component-based design of a run-time checker, identify its components and their requirements, and evaluate existing state of the art tools instantiating each component

Run-time checking multi-threaded java programs

Assertion checking traditionally focused on state-based properties. In a multi-threaded environment, approaches based on sharedstate require complex locking mechanisms to ensure that specifications are checked atomically (in the same state). In addition to this increased complexity, locks also negatively affect performance. In this paper, we extend both the underlying theory and the practical implementation of SAGA, a run-time checker for single-threaded Java programs, to multi-threading, while avoiding locks

Being and Change: Reasoning About Invariance

We introduce a new way of reasoning about invariance in terms of foot-prints in a Hoare logic for recursive programs with (unbounded) arrays. A foot-print of a statement is a predicate that describes that part of the state that can be changed by the statement. We define invariance of an assertion with respect to a foot-print by means of a logical operation. This new Hoare logic is applied in a new simpler and modular proof of correctness of the well-known Quicksort sorting algorithm

Effects of mixing on evolution of hydrocarbon ratios in the troposphere

Nonmethane hydrocarbon (NMHC) concentration ratios provide useful indicators of tropospheric oxidation and transport processes. However, the influences of both photochemical and mixing processes are inextricably linked in the evolution of these ratios. We present a model for investigating these influences by combining the transport treatment of the Lagrangian particle dispersion model FLEXPART with an ultrasimple (i.e., constant OH concentration) chemical treatment. Required model input includes NMHC emission ratios, but not ad hoc assumed background NMHC concentrations. The model results give NMHC relationships that can be directly compared, in a statistical manner, with measurements. The measured concentration ratios of the longest-lived alkanes show strong deviations from purely kinetic behavior, which the model nicely reproduces. In contrast, some measured aromatic ratio relationships show even stronger deviations that are not well reproduced by the model for reasons that are not understood. The model-measurement comparisons indicate that the interaction of mixing and photochemical processing prevent a simple interpretation of "photochemical age," but that the average age of any particular NMHC can be well defined and can be approximated by a properly chosen and interpreted NMHC ratio. In summary, the relationships of NMHC concentration ratios not only yield useful measures of photochemical processing in the troposphere, but also provide useful test of the treatment of mixing and chemical processing in chemical transport models. Copyright 2007 by the American Geophysical Union

Combining Monitoring with Run-time Assertion Checking

We develop a new technique for Run-time Checking for two object-oriented languages: Java and the Abstract Behavioral Specification language ABS. In object-oriented languages, objects communicate by sending each other messages. Assuming encapsulation, the behavior of objects is completely determined by the order of the messages, and their content. Traditional methods for Run-time Checking focus either exclusively on the description and testing of the order of the messages (Monitoring), or they focus on specifying and testing the content of those messages (Run-time Assertion Checking). Our method combines Monitoring with Run-time Assertion Checking.The basic idea behind our technique is that the behavior of objects can be described formally by means of an attribute grammar extended with assertions. The underlying (context-free) grammar specifies the valid orderings of the messages, the attributes define properties of the contents of the messages, and assertions specify the desired values of those properties. We develop a new Run-time Checker for attribute grammars in the form of a meta-program in the language Rascal and applied the Run-time Checker to an industrial case of the e-commerce company Fredhopper. We also investigated the efficiency of the run-time checker, and successfully discovered and solved several bugs in the Fredhopper software.Algorithms and the Foundations of Software technolog