261,371 research outputs found
Satisfiability of General Intruder Constraints with and without a Set Constructor
Many decision problems on security protocols can be reduced to solving
so-called intruder constraints in Dolev Yao model. Most constraint solving
procedures for protocol security rely on two properties of constraint systems
called monotonicity and variable origination. In this work we relax these
restrictions by giving a decision procedure for solving general intruder
constraints (that do not have these properties) that stays in NP. Our result
extends a first work by L. Mazar\'e in several directions: we allow non-atomic
keys, and an associative, commutative and idempotent symbol (for modeling
sets). We also discuss several new applications of the results.Comment: Submitted to the Special issue of Information and Computation on
Security and Rewriting Techniques (SecReT), 2011. 59 page
The matching relaxation for a class of generalized set partitioning problems
This paper introduces a discrete relaxation for the class of combinatorial
optimization problems which can be described by a set partitioning formulation
under packing constraints. We present two combinatorial relaxations based on
computing maximum weighted matchings in suitable graphs. Besides providing dual
bounds, the relaxations are also used on a variable reduction technique and a
matheuristic. We show how that general method can be tailored to sample
applications, and also perform a successful computational evaluation with
benchmark instances of a problem in maritime logistics.Comment: 33 pages. A preliminary (4-page) version of this paper was presented
at CTW 2016 (Cologne-Twente Workshop on Graphs and Combinatorial
Optimization), with proceedings on Electronic Notes in Discrete Mathematic
Four payment models for the multi-mode resource constrained project scheduling problem with discounted cash flows
In this paper, the multi-mode resource constrained project scheduling problem with discounted cash flows is considered. The objective is the maximization of the net present value of all cash flows. Time value of money is taken into consideration, and cash in- and outflows are associated with activities and/or events. The resources can be of renewable, nonrenewable, and doubly constrained resource types. Four payment models are considered: Lump sum payment at the terminal event, payments at prespecified event nodes, payments at prespecified time points and progress payments. For finding solutions to problems proposed, a
genetic algorithm (GA) approach is employed, which uses a special crossover operator that can exploit the multi-component nature of the problem. The models are investigated at the hand of an example problem. Sensitivity analyses are performed over the mark up and the discount rate. A set of 93 problems from literature are solved under the four different payment models and resource type combinations with the GA approach employed resulting in satisfactory computation times. The GA approach is compared with a domain specific heuristic for the lump sum payment case with renewable resources and is shown to outperform it
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