Unsatisfiability proofs for distributed clause-sharing SAT solvers

Distributed clause-sharing SAT solvers can solve problems up to one hundred times faster than sequential SAT solvers by sharing derived information among multiple sequential solvers working on the same problem. Unlike sequential solvers, however, distributed solvers have not been able to produce proofs of unsatisfiability in a scalable manner, which has limited their use in critical applications. In this paper, we present a method to produce unsatisfiability proofs for distributed SAT solvers by combining the partial proofs produced by each sequential solver into a single, linear proof. Our approach is more scalable and general than previous explorations for parallel clause-sharing solvers, allowing use on distributed solvers without shared memory. We propose a simple sequential algorithm as well as a fully distributed algorithm for proof composition. Our empirical evaluation shows that for large-scale distributed solvers (100 nodes of 16 cores each), our distributed approach allows reliable proof composition and checking with reasonable overhead. We analyze the overhead and discuss how and where future efforts may further improve performance

Fiskalische Kosten einer steuerlichen Förderung von Forschung und Entwicklung in Deutschland - Eine empirische Analyse verschiedener Gestaltungsoptionen

Der Beitrag berechnet die Aufkommensausfälle verschiedener Gestaltungsmodelle für eine steuerliche Forschungsförderung in Deutschland auf Basis eines Mikrosimulationsmodells. Die fiskalischen Kosten betragen zwischen 464 Mio. € und 5.701 Mio. €. Eine Erstattungsoption der Steuergutschrift über die Gewerbe- und Körperschaftsteuerschuld hinaus ist unerlässlich, da sonst etwa ein Drittel der Unternehmen nicht oder nur teilweise in den Genuss der Förderung kommen würde und sich dadurch starke Verzerrungen zwischen ertragsstarken und ertragsschwachen Unternehmen ergeben. Eine Differenzierung der Fördersätze für KMU und große Unternehmen kann die Aufkommensausfälle wirksam begrenzen. Eine Kappungsgrenze in Höhe eines absoluten Betrages ist wegen der Verzerrungen innerhalb der Gruppe großer Unternehmen ungünstig. Als besonders pragmatisch erscheint eine Verrechnung der Steuergutschrift mit der abzuführenden Lohnsteuer

Migrating Solver State

We present approaches to store and restore the state of a SAT solver, allowing us to migrate the state between different compute resources, or even between different solvers. This can be used in many ways, e.g., to improve the fault tolerance of solvers, to schedule SAT problems on a restricted number of cores, or to use dedicated preprocessing tools for inprocessing. We identify a minimum viable subset of the solver state to migrate such that the loss of performance is small. We then present and implement two different approaches to state migration: one approach stores the state at the end of a solver run whereas the other approach stores the state continuously as part of the proof trace. We show that our approaches enable the generation of correct models and valid unsatisfiability proofs. Experimental results confirm that the overhead is reasonable and that in several cases solver performance actually improves

Enhancing accessibility to portraits: the Elias Goldensky Collection

Thesis (M.A.)--University of Rochester and George Eastman Museum, Photographic Preservation and Collections Management, 2017.While cataloging standards for museums provide general best practices, there are no specific guidelines for cataloging photographic portraits in detail. Portraiture poses challenges in cataloging, as many commercial portrait collections often contain unknown sitters. Utilizing a selection of 438 portraits taken by Philadelphia photographer Elias Goldensky and held in the collection of the George Eastman Museum (GEM), this project seeks to enhance accessibility to individual portraits and variants within the collection through the use of descriptive fashion attributes. To facilitate retrieval of these photographs in object searches, I have brought the cataloging records up to current GEM standards, traced the relational connections between variant prints, and organized a collection-specific controlled vocabulary, based on national standards, to make the portraits individually searchable