Revisiting the Problem of Searching on a Line

We revisit the problem of searching for a target at an unknown location on a line when given upper and lower bounds on the distance D that separates the initial position of the searcher from the target. Prior to this work, only asymptotic bounds were known for the optimal competitive ratio achievable by any search strategy in the worst case. We present the first tight bounds on the exact optimal competitive ratio achievable, parameterized in terms of the given bounds on D, along with an optimal search strategy that achieves this competitive ratio. We prove that this optimal strategy is unique. We characterize the conditions under which an optimal strategy can be computed exactly and, when it cannot, we explain how numerical methods can be used efficiently. In addition, we answer several related open questions, including the maximal reach problem, and we discuss how to generalize these results to m rays, for any m >= 2

Vega - a user-centered approach to the distributed visualization of geometric algorithms

We present a new approach to the distributed visualization of geometric algorithms that emphasizes the position of the end user. Concepts are introduced that enable a more flexible usage of visualized geometric algorithms, while keeping the task of adapting existing algorithms to the new scheme as simple as possible. A main proposition is that interactivity should not be built into the visualized algorithms, but into the visualizing system. With this in mind, we devise a visualization model for geometric algorithms that incorporates strong algorithm execution control, flexible manipulation of geometric input/output data and adjustable view attributes. The new visualization model is implemented in the Vega system. Vega offers distributed visualization of geometric algorithms based on source code annotation and supports the standard libraries LEDA and CGAL. (orig.)SIGLEAvailable from TIB Hannover: RR 5165(117) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDeutsche Forschungsgemeinschaft (DFG), Bonn (Germany)DEGerman

Vega - a user-centered approach to the distributed visualization of geometric algorithms

We present a new approach to the distributed visualization of geometric algorithms that emphasizes the position of the end user. Concepts are introduced that enable a more flexible usage of visualized geometric algorithms, while keeping the task of adapting existing algorithms to the new scheme as simple as possible. A main proposition is that interactivity should not be built into the visualized algorithms, but into the visualizing system. With this in mind, we devise a visualization model for geometric algorithms that incorporates strong algorithm execution control, flexible manipulation of geometric input/output data and adjustable view attributes. The new visualization model is implemented in the Vega system. Vega offers distributed visualization of geometric algorithms based on source code annotation and supports the standard libraries LEDA and CGAL. (orig.)SIGLEAvailable from TIB Hannover: RR 5165(117) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDeutsche Forschungsgemeinschaft (DFG), Bonn (Germany)DEGerman