97 research outputs found
A reusable iterative optimization software library to solve combinatorial problems with approximate reasoning
Real world combinatorial optimization problems such as scheduling are
typically too complex to solve with exact methods. Additionally, the problems
often have to observe vaguely specified constraints of different importance,
the available data may be uncertain, and compromises between antagonistic
criteria may be necessary. We present a combination of approximate reasoning
based constraints and iterative optimization based heuristics that help to
model and solve such problems in a framework of C++ software libraries called
StarFLIP++. While initially developed to schedule continuous caster units in
steel plants, we present in this paper results from reusing the library
components in a shift scheduling system for the workforce of an industrial
production plant.Comment: 33 pages, 9 figures; for a project overview see
http://www.dbai.tuwien.ac.at/proj/StarFLIP
Endgame problems of Sim-like graph Ramsey avoidance games are PSPACE-complete
AbstractIn Sim, two players compete on a complete graph of six vertices (K6). The players alternate in coloring one as yet uncolored edge using their color. The player who first completes a monochromatic triangle (K3) loses. Replacing K6 and K3 by arbitrary graphs generalizes Sim to graph Ramsey avoidance games. Given an endgame position in these games, the problem of deciding whether the player who moves next has a winning strategy is shown to be PSPACE-complete. It can be reduced from the problem of whether the first player has a winning strategy in the game Gpos(POSCNF) (Schaefer, J. Comput. System Sci. 16 (2) (1978) 185β225). The following game variants are also shown to have PSPACE-complete endgame problems: (1) completing a monochromatic subgraph isomorphic to A is forbidden and the player who is first unable to move loses, (2) both players are allowed to color one or more edges in each move, (3) more than two players take part in the game, and (4) each player has to avoid a separate graph. In all results, the graphs to be avoided can be restricted to the bowtie graph (β, i.e., two triangles with one common vertex)
On the Lengths of Symmetry Breaking-Preserving Games on Graphs
Given a graph , we consider a game where two players, and ,
alternatingly color edges of in red and in blue respectively. Let be
the maximum number of moves in which is able to keep the red and the blue
subgraphs isomorphic, if plays optimally to destroy the isomorphism. This
value is a lower bound for the duration of any avoidance game on under the
assumption that plays optimally. We prove that if is a path or a cycle
of odd length , then . The lower
bound is based on relations with Ehrenfeucht games from model theory. We also
consider complete graphs and prove that .Comment: 20 page
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