63 research outputs found
Avoiding Braess' Paradox through Collective Intelligence
In an Ideal Shortest Path Algorithm (ISPA), at each moment each router in a
network sends all of its traffic down the path that will incur the lowest cost
to that traffic. In the limit of an infinitesimally small amount of traffic for
a particular router, its routing that traffic via an ISPA is optimal, as far as
cost incurred by that traffic is concerned. We demonstrate though that in many
cases, due to the side-effects of one router's actions on another routers
performance, having routers use ISPA's is suboptimal as far as global aggregate
cost is concerned, even when only used to route infinitesimally small amounts
of traffic. As a particular example of this we present an instance of Braess'
paradox for ISPA's, in which adding new links to a network decreases overall
throughput. We also demonstrate that load-balancing, in which the routing
decisions are made to optimize the global cost incurred by all traffic
currently being routed, is suboptimal as far as global cost averaged across
time is concerned. This is also due to "side-effects", in this case of current
routing decision on future traffic.
The theory of COllective INtelligence (COIN) is concerned precisely with the
issue of avoiding such deleterious side-effects. We present key concepts from
that theory and use them to derive an idealized algorithm whose performance is
better than that of the ISPA, even in the infinitesimal limit. We present
experiments verifying this, and also showing that a machine-learning-based
version of this COIN algorithm in which costs are only imprecisely estimated (a
version potentially applicable in the real world) also outperforms the ISPA,
despite having access to less information than does the ISPA. In particular,
this COIN algorithm avoids Braess' paradox.Comment: 28 page
Game Theory Models for the Verification of the Collective Behaviour of Autonomous Cars
The collective of autonomous cars is expected to generate almost optimal
traffic. In this position paper we discuss the multi-agent models and the
verification results of the collective behaviour of autonomous cars. We argue
that non-cooperative autonomous adaptation cannot guarantee optimal behaviour.
The conjecture is that intention aware adaptation with a constraint on
simultaneous decision making has the potential to avoid unwanted behaviour. The
online routing game model is expected to be the basis to formally prove this
conjecture.Comment: In Proceedings FVAV 2017, arXiv:1709.0212
Macroscopic modeling and simulations of room evacuation
We analyze numerically two macroscopic models of crowd dynamics: the
classical Hughes model and the second order model being an extension to
pedestrian motion of the Payne-Whitham vehicular traffic model. The desired
direction of motion is determined by solving an eikonal equation with density
dependent running cost, which results in minimization of the travel time and
avoidance of congested areas. We apply a mixed finite volume-finite element
method to solve the problems and present error analysis for the eikonal solver,
gradient computation and the second order model yielding a first order
convergence. We show that Hughes' model is incapable of reproducing complex
crowd dynamics such as stop-and-go waves and clogging at bottlenecks. Finally,
using the second order model, we study numerically the evacuation of
pedestrians from a room through a narrow exit.Comment: 22 page
Simulating Drivers' Decision-making Under Information Dissemination
Nos dias de hoje, informação de trânsito precisa e actualizada é bastante importante para os viajantes chegarem ao seu destino mais rápido e em segurança. É neste aspecto que os Sistemas de Informação ao Viajante ou Advanced Travellers Information Systems (ATIS), se inserem nos Sistemas Inteligentes de Transporte. Tirando partido das novos serviços Web e tecnologias wireless de comunicação estes sistemas fornecem informação valiosa antes, durante e até após a viagem, sendo, sistemas que recolhem, analisam e transmitem informação útil para os viajantes.O objectivo deste trabalho é analisar o comportamento dos condutores num meio com disseminação de informação. Assim, será necessário criar uma plataforma que possibilite a implementação de condutores e infraestruturas de gestão e controlo utilizado os Sistemas Multi-Agente (MAS) como paradigma de modelação para a criação da nossa sociedade artificial e como paradigma de programação no aspecto de análise e simulação de todo o processo
The quality of sustainability and the nature of open source software
The aim is to categorise Open Source Software as a commons based production process and resource. The definition of the commons is always accompanied by the doubt about its sustainability, the so-called "tragedy of the commons." Therefore it is worth to have a closer look on Open Source and why a "tragedy" does not appear
Pedestrian flows in bounded domains with obstacles
In this paper we systematically apply the mathematical structures by
time-evolving measures developed in a previous work to the macroscopic modeling
of pedestrian flows. We propose a discrete-time Eulerian model, in which the
space occupancy by pedestrians is described via a sequence of Radon positive
measures generated by a push-forward recursive relation. We assume that two
fundamental aspects of pedestrian behavior rule the dynamics of the system: On
the one hand, the will to reach specific targets, which determines the main
direction of motion of the walkers; on the other hand, the tendency to avoid
crowding, which introduces interactions among the individuals. The resulting
model is able to reproduce several experimental evidences of pedestrian flows
pointed out in the specialized literature, being at the same time much easier
to handle, from both the analytical and the numerical point of view, than other
models relying on nonlinear hyperbolic conservation laws. This makes it
suitable to address two-dimensional applications of practical interest, chiefly
the motion of pedestrians in complex domains scattered with obstacles.Comment: 25 pages, 9 figure
- …