Verification of the Tree-Based Hierarchical Read-Copy Update in the Linux Kernel

Read-Copy Update (RCU) is a scalable, high-performance Linux-kernel synchronization mechanism that runs low-overhead readers concurrently with updaters. Production-quality RCU implementations for multi-core systems are decidedly non-trivial. Giving the ubiquity of Linux, a rare "million-year" bug can occur several times per day across the installed base. Stringent validation of RCU's complex behaviors is thus critically important. Exhaustive testing is infeasible due to the exponential number of possible executions, which suggests use of formal verification. Previous verification efforts on RCU either focus on simple implementations or use modeling languages, the latter requiring error-prone manual translation that must be repeated frequently due to regular changes in the Linux kernel's RCU implementation. In this paper, we first describe the implementation of Tree RCU in the Linux kernel. We then discuss how to construct a model directly from Tree RCU's source code in C, and use the CBMC model checker to verify its safety and liveness properties. To our best knowledge, this is the first verification of a significant part of RCU's source code, and is an important step towards integration of formal verification into the Linux kernel's regression test suite.Comment: This is a long version of a conference paper published in the 2018 Design, Automation and Test in Europe Conference (DATE

Using ICT to Foster (Pre) Reading and Writing Skills in Young Children

This study examines how technology can support the development of emergent reading and writing skills in four- to five-year-old children. The research was conducted with PictoPal, an intervention which features a software package that uses images and text in three main activity areas: reading, writing, and authentic applications. This article reports on the effects of the PictoPal intervention on pupil literacy and communication skills. Two small-scale studies were conducted. Observation results from the first study showed that children are able to work independently with the program after a few instruction sessions. The second study showed a statistically significant learning effect of experimental versus control group scores after two months of using PictoPal in the classroom under the guidance of a parent volunteer. Further research is needed to arrive at a better understanding of these learning gains with a larger group of pupils

Finitely generated nilpotent group C*-algebras have finite nuclear dimension

We show that group C*-algebras of finitely generated, nilpotent groups have finite nuclear dimension. It then follows, from a string of deep results, that the C*-algebra $A$ generated by an irreducible representation of such a group has decomposition rank at most 3. If, in addition, $A$ satisfies the universal coefficient theorem, another string of deep results shows it is classifiable by its Elliott invariant and is approximately subhomogeneous. We give a large class of irreducible representations of nilpotent groups (of arbitrarily large nilpotency class) that satisfy the universal coefficient theorem and therefore are classifiable and approximately subhomogeneous.Comment: Fixed typos. Question 5.1 of the previous version was already answered in the literature; we have provided the appropriate referenc

Land Grant Application- McKenney, Abner (Saco)

Land grant application submitted to the Maine Land Office on behalf of Abner McKenney for service in the Revolutionary War, by their widow Sarah.https://digitalmaine.com/revolutionary_war_me_land_office/1626/thumbnail.jp

On the Dynamics and Acoustics of Cloud Cavitation on an Oscillating Hydrofoil

Observations have been made of the growth and collapse of surface and cloud cavitation on a finite aspect ratio hydrofoil oscillating in pitch. The cavitation was recorded using both still and high-speed motion picture photography, and the variations with cavitation number and reduced frequency of oscillation were investigated. The noise generated by the cavity collapse was also measured and analyzed. The acoustic signals associated with individual cavity collapse events have been synchronized with the motion pictures, providing insights into the correspondence between the flow structures involved in the cavity collapse process and the sound generated by them