Prototyping Formal System Models with Active Objects

We propose active object languages as a development tool for formal system models of distributed systems. Additionally to a formalization based on a term rewriting system, we use established Software Engineering concepts, including software product lines and object orientation that come with extensive tool support. We illustrate our modeling approach by prototyping a weak memory model. The resulting executable model is modular and has clear interfaces between communicating participants through object-oriented modeling. Relaxations of the basic memory model are expressed as self-contained variants of a software product line. As a modeling language we use the formal active object language ABS which comes with an extensive tool set. This permits rapid formalization of core ideas, early validity checks in terms of formal invariant proofs, and debugging support by executing test runs. Hence, our approach supports the prototyping of formal system models with early feedback.Comment: In Proceedings ICE 2018, arXiv:1810.0205

Minimizing the number of lattice points in a translated polygon

The parametric lattice-point counting problem is as follows: Given an integer matrix $A \in Z^{m \times n}$, compute an explicit formula parameterized by $b \in R^m$ that determines the number of integer points in the polyhedron $\{x \in R^n : Ax \leq b\}$. In the last decade, this counting problem has received considerable attention in the literature. Several variants of Barvinok's algorithm have been shown to solve this problem in polynomial time if the number $n$ of columns of $A$ is fixed. Central to our investigation is the following question: Can one also efficiently determine a parameter $b$ such that the number of integer points in $\{x \in R^n : Ax \leq b\}$ is minimized? Here, the parameter $b$ can be chosen from a given polyhedron $Q \subseteq R^m$. Our main result is a proof that finding such a minimizing parameter is $NP$-hard, even in dimension 2 and even if the parametrization reflects a translation of a 2-dimensional convex polygon. This result is established via a relationship of this problem to arithmetic progressions and simultaneous Diophantine approximation. On the positive side we show that in dimension 2 there exists a polynomial time algorithm for each fixed $k$ that either determines a minimizing translation or asserts that any translation contains at most $1 + 1/k$ times the minimal number of lattice points

Obstructions to weak decomposability for simplicial polytopes

Provan and Billera introduced notions of (weak) decomposability of simplicial complexes as a means of attempting to prove polynomial upper bounds on the diameter of the facet-ridge graph of a simplicial polytope. Recently, De Loera and Klee provided the first examples of simplicial polytopes that are not weakly vertex-decomposable. These polytopes are polar to certain simple transportation polytopes. In this paper, we refine their analysis to prove that these $d$-dimensional polytopes are not even weakly $O(\sqrt{d})$-decomposable. As a consequence, (weak) decomposability cannot be used to prove a polynomial version of the Hirsch conjecture

R&D Collaboration between CERN and Industrial Companies: Organizational and Spatial Aspects

The findings of fundamental research in fields like fusion research, space research or high energy physics stimulate innovation and technological progress in industry. Although R&D collaborations between companies already have been investigated in detail, R&D collaborations between companies and large-scale research centers are not well understood. This report is a part of a PhD study which aimed at providing answers to the question of how to best organise and manage R&D collaborations between industry and scientific centers. This research problem is analysed using CERN, the European Laboratory for Particle Physics, as a case study. A conceptual framework is designed based on previous findings in Transaction Cost Economics, Strategic Management and the findings of related Empirical Studies. The conceptual framework captures the dynamics of R&D collaborations from conceptual design to managerial implementation: Besides the design of the collaboration format, one should pay particular attention to the selection of the collaboration partner, the negotiation of the collaboration agreement and the implementation of the collaboration. Based on the conceptual framework, general problems and success factors of innovative collaborations are identified. The collected empirical evidence from 21 cases of R&D collaborations between the electronics and data communications industry and CERN is used to answer the research problem. The empirical data was gathered in personal interviews with company engineers and CERN engineers who were directly involved in the selected R&D collaborations. The exploratory analysis leads to the identification of critical issues concerning the design of the collaboration format, the selection of the partner, the negotiation of the agreement and the implementation of the project. A deeper analysis of four R&D collaborations investigates how the collaboration partners organised the projects in order to ensure effective communication and common learning despite geographical separation. Apart from developing a conceptual framework for analysing R&D collaborations, the contribution of this study to the theoretical debate is to add more nuance to observations in the current literature regarding factors resulting in successful collaborations. More specifically, the motivations for taking part in R&D collaborations and the differences between small and large companies are elaborated here in more detail. Second, the importance of informal networks and the role of trust in such undertakings can be demonstrated in a more differentiated way. Third, the link between specific communication patterns and the location of the collaboration partners is elaborated.Series: IIR-Discussion Paper

Ökologische Bienenhaltung - was zeichnet sie aus?

Unter ökologischer Bienenhaltung ist eine naturnahe, artgemäße Bienenhaltung zu verstehen, die den Grundsätzen der ökologischen Landbewirtschaftung folgt. Ziel der ökologischen Bienenhaltung ist eine hohe Qualität der Imkereiprodukte, die sich dadurch auszeichnen, dass sie unverfälscht sind und eine niedrige Belastung mit Schadstoffen aufweisen. Wie funktioniert ökologische Bienenhaltung, was ist bei ihr anders

October 4, 1962

https://scholarlycommons.obu.edu/arbaptnews/1243/thumbnail.jp

On the Shadow Simplex Method for Curved Polyhedra

We study the simplex method over polyhedra satisfying certain “discrete curvature” lower bounds, which enforce that the boundary always meets vertices at sharp angles. Motivated by linear programs with totally unimodular constraint matrices, recent results of Bonifas et al (SOCG 2012), Brunsch and Röglin (ICALP 2013), and Eisenbrand and Vempala (2014) have improved our understanding of such polyhedra. We develop a new type of dual analysis of the shadow simplex method which provides a clean and powerful tool for improving all previously mentioned results. Our methods are inspired by the recent work of Bonifas and the first named author [4], who analyzed a remarkably similar process as part of an algorithm for the Closest Vector Problem with Preprocessing. For our first result, we obtain a constructive diameter bound of O( n2 ln n ) for n-dimensional polyhedra with curvature parameter 2 [0, 1]. For the class of polyhedra arising from totally unimodular constraint matrices, this implies a bound of O(n3 ln n). For linear optimization, given an initial feasible vertex, we show that an optimal vertex can be found using an expected O( n3 ln n ) simplex pivots, each requiring O(mn) time to compute. An initial feasible solutioncan be found using O(mn3 ln n ) pivot steps