Bidirectional A*: comparing balanced and symmetric heuristic methods

A widely known algorithm for ¯nding the shortest path in a network is Bidirectional A*. The version of bidirectional A* that is considered the most appropriatehitherto, uses so-called balanced heuristic estimates. In this paper, we focus on symmetric heuristic estimates. First, we show that bidirectional A* using the symmetricheuristic estimate provides us with a feasible approximation. Next a framework is introduced for solving the shortest path problem exactly. It turns out that both thebalanced and the symmetric heuristic estimate are instances of a general bidirectional A* framework. The symmetric instance surpasses the balanced instance in space andtime.operations research;graph theory;network flow;search;shortest path

A new bidirectional algorithm for shortest paths

For finding a shortest path in a network the bidirectional A* algorithm is a widely known algorithm.An A* instance requires a heuristic estimate, a real-valued function on the set of nodes.The version of bidirectional~A* that is considered the most appropriate in literature hitherto,uses so-called balanced heuristic estimates.This means that the two estimates of the two directions are in balance, i.e., their sum is a constant value.In this paper, we do not restrict ourselves any longer to balanced heuristics.A generalized version of bidirectional A* is proposed, where the heuristic estimate does not need to be balanced.This new version turns out to be faster than the one with the balanced heuristic.shortest path;bidirectional search;road network search

Does Risk Seeking Drive Asset Prices? A stochastic dominance analysis of aggregate investor preferences

We investigate whether risk seeking or non-concave utility functions can help to explainthe cross-sectional pattern of stock returns. For this purpose, we analyze the stochasticdominance efficiency classification of the value-weighted market portfolio relative tobenchmark portfolios based on market capitalization, book-to-market equity ratio andmomentum. We use various existing and novel stochastic dominance criteria that accountfor the possibility that investors exhibit local risk seeking behavior. Our results suggestthat Markowitz type utility functions, with risk aversion for losses and risk seeking forgains, can capture the cross-sectional pattern of stock returns. The low average yield onbig caps, growth stocks and past losers may reflect investors' twin desire for downsideprotection in bear markets and upside potential in bull markets.asset pricing;stochastic dominance;prospect theory;risk seeking;specification error

Yet another bidirectional algorithm for shortest paths

For finding a shortest path in a network the bidirectional~A* algorithm is a widely known algorithm. An A* instance requires a heuristic estimate, a real-valued function on the set of nodes. %This algorithm distinguishes between the main phase and the postprocessing phase. %As long as the search processes of the two sides do not meet, we are in the main phase. %As soon as a meeting point is obtained, the post-phase is in progress. \\\\ The version of bidirectional~A* that is considered the most appropriate in literature hitherto, uses so-called balanced heuristic estimates. This means that the two estimates of the two directions are in balance, i.e., their sum is a constant value. In this paper, we do not restrict ourselves any longer to balanced heuristics. A generalized version of bidirectional A* is proposed, where the heuristic estimate does not need to be balanced. This new version turns out to be faster than the one with the balanced heuristic.shortest path;bidirectional search;road network search

Semirelativistic stability of N-boson systems bound by 1/r pair potentials

We analyze a system of self-gravitating identical bosons by means of a semirelativistic Hamiltonian comprising the relativistic kinetic energies of the involved particles and added (instantaneous) Newtonian gravitational pair potentials. With the help of an improved lower bound to the bottom of the spectrum of this Hamiltonian, we are able to enlarge the known region for relativistic stability for such boson systems against gravitational collapse and to sharpen the predictions for their maximum stable mass.Comment: 11 pages, considerably enlarged introduction and motivation, remainder of the paper unchange

A Study of the Flora Found in the Area of North Bay, Ontario, Canada

This 20 page thesis describes natural settings found in the islands of North Bay, Ontario and the technical process of collecting plant specimens in this region. A full listing of specimens collected and statistics are included

The Two Modes of Visual Processing: Implications for Spatial Orientation

The roles of the focal and ambient visual systems in spatial orientation are discussed. The two modes are defined and compared. The contribution of each system is illustrated through examples such as spatial disorientation/motion sickness, vehicle guidance/night driving, visual narrowing under stress/cortical brain damage, and aircraft instrumentation. Emphasis is placed on the need for testing procedures for the ambient system