81 research outputs found
Aggregating Dependency Graphs into Voting Agendas in Multi-Issue Elections
Many collective decision making problems have a
combinatorial structure: the agents involved must
decide on multiple issues and their preferences over
one issue may depend on the choices adopted for
some of the others. Voting is an attractive method
for making collective decisions, but conducting a
multi-issue election is challenging. On the one hand,
requiring agents to vote by expressing their preferences
over all combinations of issues is computationally
infeasible; on the other, decomposing the
problem into several elections on smaller sets of
issues can lead to paradoxical outcomes. Any pragmatic
method for running a multi-issue election will
have to balance these two concerns. We identify
and analyse the problem of generating an agenda
for a given election, specifying which issues to vote
on together in local elections and in which order to
schedule those local elections
Adjoint computations by algorithmic differentiation of a parallel solver for time-dependent PDEs
A computational fluid dynamics code is differentiated using algorithmic
differentiation (AD) in both tangent and adjoint modes. The two novelties of
the present approach are 1) the adjoint code is obtained by letting the AD tool
Tapenade invert the complete layer of message passing interface (MPI)
communications, and 2) the adjoint code integrates time-dependent, non-linear
and dissipative (hence physically irreversible) PDEs with an explicit time
integration loop running for ca. time steps. The approach relies on
using the Adjoinable MPI library to reverse the non-blocking communication
patterns in the original code, and by controlling the memory overhead induced
by the time-stepping loop with binomial checkpointing. A description of the
necessary code modifications is provided along with the validation of the
computed derivatives and a performance comparison of the tangent and adjoint
codes.Comment: Submitted to Journal of Computational Scienc
Rationalisation of Profiles of Abstract Argumentation Frameworks: Characterisation and Complexity
Rationalisation of Profiles of Abstract Argumentation Frameworks
International audienceDifferent agents may have different points of view. This can be modelled using different abstract argumentation frameworks , each consisting of a set of arguments and a binary attack-relation between them. A question arising in this context is whether the diversity of views observed in such a profile of argumentation frameworks is consistent with the assumption that every individual argumentation framework is induced by a combination of, first, some basic factual attack-relation between the arguments and, second, the personal preferences of the agent concerned. We treat this question of rationalisability of a profile as an algorithmic problem and identify tractable and intractable cases. This is useful for understanding what types of profiles can reasonably be expected to come up in a multiagent system
Sequential Deliberation for Social Choice
In large scale collective decision making, social choice is a normative study
of how one ought to design a protocol for reaching consensus. However, in
instances where the underlying decision space is too large or complex for
ordinal voting, standard voting methods of social choice may be impractical.
How then can we design a mechanism - preferably decentralized, simple,
scalable, and not requiring any special knowledge of the decision space - to
reach consensus? We propose sequential deliberation as a natural solution to
this problem. In this iterative method, successive pairs of agents bargain over
the decision space using the previous decision as a disagreement alternative.
We describe the general method and analyze the quality of its outcome when the
space of preferences define a median graph. We show that sequential
deliberation finds a 1.208- approximation to the optimal social cost on such
graphs, coming very close to this value with only a small constant number of
agents sampled from the population. We also show lower bounds on simpler
classes of mechanisms to justify our design choices. We further show that
sequential deliberation is ex-post Pareto efficient and has truthful reporting
as an equilibrium of the induced extensive form game. We finally show that for
general metric spaces, the second moment of of the distribution of social cost
of the outcomes produced by sequential deliberation is also bounded
Religion between Nation and Europe: The French and Belgian ‘No’ to the Christian Heritage of Europe
High performance liquid chromatography/electrospray tandem mass spectrometry of polycyclic aromatic hydrocarbons
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