75 research outputs found
Begutachtung der Kriminalprognose: Spielt die Psychopathologie noch eine Rolle?
Zusammenfassung: Eine Fülle von standardisierten Instrumenten ermöglicht mittlerweile an empirischen Daten ausgerichtete Aussagen zur Kriminalprognose. Der vorliegende Beitrag zeigt am Beispiel von weit verbreiteten und für die praktische Anwendung relevanten Verfahren (Violence Risk Appraisal Guide, Static-99, Historical Clinical Risk Management-20, Psychopathy Checklist-Revised) Limitationen der Anwendbarkeit solcher Instrumente auf. Vor diesem Hintergrund soll deutlich werden, dass der psychopathologische Arbeitsansatz durch den Einsatz standardisierter kriminalprognostischer Instrumente nicht überflüssig, sondern im Sinne eines integrativen Vorgehens sinnvoll ergänzt wir
Quasirandom Load Balancing
We propose a simple distributed algorithm for balancing indivisible tokens on
graphs. The algorithm is completely deterministic, though it tries to imitate
(and enhance) a random algorithm by keeping the accumulated rounding errors as
small as possible.
Our new algorithm surprisingly closely approximates the idealized process
(where the tokens are divisible) on important network topologies. On
d-dimensional torus graphs with n nodes it deviates from the idealized process
only by an additive constant. In contrast to that, the randomized rounding
approach of Friedrich and Sauerwald (2009) can deviate up to Omega(polylog(n))
and the deterministic algorithm of Rabani, Sinclair and Wanka (1998) has a
deviation of Omega(n^{1/d}). This makes our quasirandom algorithm the first
known algorithm for this setting which is optimal both in time and achieved
smoothness. We further show that also on the hypercube our algorithm has a
smaller deviation from the idealized process than the previous algorithms.Comment: 25 page
The Price of Anarchy for Selfish Ring Routing is Two
We analyze the network congestion game with atomic players, asymmetric
strategies, and the maximum latency among all players as social cost. This
important social cost function is much less understood than the average
latency. We show that the price of anarchy is at most two, when the network is
a ring and the link latencies are linear. Our bound is tight. This is the first
sharp bound for the maximum latency objective.Comment: Full version of WINE 2012 paper, 24 page
Malicious Bayesian Congestion Games
In this paper, we introduce malicious Bayesian congestion games as an
extension to congestion games where players might act in a malicious way. In
such a game each player has two types. Either the player is a rational player
seeking to minimize her own delay, or - with a certain probability - the player
is malicious in which case her only goal is to disturb the other players as
much as possible.
We show that such games do in general not possess a Bayesian Nash equilibrium
in pure strategies (i.e. a pure Bayesian Nash equilibrium). Moreover, given a
game, we show that it is NP-complete to decide whether it admits a pure
Bayesian Nash equilibrium. This result even holds when resource latency
functions are linear, each player is malicious with the same probability, and
all strategy sets consist of singleton sets. For a slightly more restricted
class of malicious Bayesian congestion games, we provide easy checkable
properties that are necessary and sufficient for the existence of a pure
Bayesian Nash equilibrium.
In the second part of the paper we study the impact of the malicious types on
the overall performance of the system (i.e. the social cost). To measure this
impact, we use the Price of Malice. We provide (tight) bounds on the Price of
Malice for an interesting class of malicious Bayesian congestion games.
Moreover, we show that for certain congestion games the advent of malicious
types can also be beneficial to the system in the sense that the social cost of
the worst case equilibrium decreases. We provide a tight bound on the maximum
factor by which this happens.Comment: 18 pages, submitted to WAOA'0
Strategyproof Mechanisms for Additively Separable Hedonic Games and Fractional Hedonic Games
Additively separable hedonic games and fractional hedonic games have received
considerable attention. They are coalition forming games of selfish agents
based on their mutual preferences. Most of the work in the literature
characterizes the existence and structure of stable outcomes (i.e., partitions
in coalitions), assuming that preferences are given. However, there is little
discussion on this assumption. In fact, agents receive different utilities if
they belong to different partitions, and thus it is natural for them to declare
their preferences strategically in order to maximize their benefit. In this
paper we consider strategyproof mechanisms for additively separable hedonic
games and fractional hedonic games, that is, partitioning methods without
payments such that utility maximizing agents have no incentive to lie about
their true preferences. We focus on social welfare maximization and provide
several lower and upper bounds on the performance achievable by strategyproof
mechanisms for general and specific additive functions. In most of the cases we
provide tight or asymptotically tight results. All our mechanisms are simple
and can be computed in polynomial time. Moreover, all the lower bounds are
unconditional, that is, they do not rely on any computational or complexity
assumptions
Facets of the Fully Mixed Nash Equilibrium Conjecture
In this work, we continue the study of the many facets of the Fully Mixed Nash Equilibrium Conjecture, henceforth abbreviated as the FMNE Conjecture, in selfish routing for the special case of n identical users over two (identical) parallel links. We introduce a new measure of Social Cost, defined to be the expectation of the square of the maximum congestion on a link; we call it Quadratic Maximum Social Cost. A Nash equilibrium is a stable state where no user can improve her (expected) latency by switching her mixed strategy; a worst-case Nash equilibrium is one that maximizes Quadratic Maximum Social Cost. In the fully mixed Nash equilibrium, allmixed strategies achieve full support. Formulated within this framework is yet another facet of the FMNE Conjecture, which states that the fully mixed Nash equilibrium is the worst-case Nash equilibrium. We present an extensive proof of the FMNE Conjecture; the proof employs a mixture of combinatorial arguments and ana-lytical estimations. Some of these analytical estimations are derived through some new bounds on generalized medians of the binomial distribution [22] we obtain, which are of independent interest.
Resource Competition on Integral Polymatroids
We study competitive resource allocation problems in which players distribute
their demands integrally on a set of resources subject to player-specific
submodular capacity constraints. Each player has to pay for each unit of demand
a cost that is a nondecreasing and convex function of the total allocation of
that resource. This general model of resource allocation generalizes both
singleton congestion games with integer-splittable demands and matroid
congestion games with player-specific costs. As our main result, we show that
in such general resource allocation problems a pure Nash equilibrium is
guaranteed to exist by giving a pseudo-polynomial algorithm computing a pure
Nash equilibrium.Comment: 17 page
Nash Social Welfare in Selfish and Online Load Balancing
In load balancing problems there is a set of clients, each wishing to select
a resource from a set of permissible ones, in order to execute a certain task.
Each resource has a latency function, which depends on its workload, and a
client's cost is the completion time of her chosen resource. Two fundamental
variants of load balancing problems are {\em selfish load balancing} (aka. {\em
load balancing games}), where clients are non-cooperative selfish players aimed
at minimizing their own cost solely, and {\em online load balancing}, where
clients appear online and have to be irrevocably assigned to a resource without
any knowledge about future requests. We revisit both selfish and online load
balancing under the objective of minimizing the {\em Nash Social Welfare},
i.e., the geometric mean of the clients' costs. To the best of our knowledge,
despite being a celebrated welfare estimator in many social contexts, the Nash
Social Welfare has not been considered so far as a benchmarking quality measure
in load balancing problems. We provide tight bounds on the price of anarchy of
pure Nash equilibria and on the competitive ratio of the greedy algorithm under
very general latency functions, including polynomial ones. For this particular
class, we also prove that the greedy strategy is optimal as it matches the
performance of any possible online algorithm
Fabry's disease and psychosis: causality or coincidence?
A 21-year-old female with Fabry's disease (FD) presented acute psychotic symptoms such as delusions, auditory hallucinations and formal thought disorders. Since the age of 14, she had suffered from various psychiatric symptoms increasing in frequency and intensity. We considered the differential diagnoses of prodromal symptoms of schizophrenia and organic schizophrenia-like disorder. Routine examinations including cognitive testing, electroencephalography and structural magnetic resonance imaging revealed no pathological findings. Additional structural and functional imaging demonstrated a minor CNS involvement of FD, yet without functional limitations. In summary our examination results support the thesis that in the case of our patient a mere coincidence of FD and psychotic symptoms is more likely than a causal connection
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