A Stackelberg game for modelling asymmetric users' behavior in grid scheduling

In traditional distributed computing the users and owners of the computational resources usually belong to the same administrative domain. Therefore all users are equally entitled to use the resources. The situation is completely different in large-scale emergent distributed computing systems, such as Grid systems, where the roles of the users are asymmetric as regards their access rights and usage of resources. Further, unlike traditional distributed computing case, Grid systems introduce hierarchical levels, which are to be taken into account for optimizing the overall system's performance. In this paper we present a Stackelberg game for modelling asymmetric users' behavior in Grid scheduling scenario. We define a two-level game with a Leader at the first level and the rest of users, called Followers, at the second one. The Leader is responsible for computing a planning of his tasks, which is usually a large fraction of the total pool of tasks in the batch. The Followers try to select the best strategy for the assignments of their tasks subject to Leader's strategy. The Stackelberg game is then translated into a hierarchical optimization problem, which is solved by Genetic Algorithm (GA) on the Leader's level and by ad hoc heuristic combined with GA on the Followers' level. We have experimentally evaluated the approach through a benchmark of static instances and report computational results for resource utilization, makespan and flowtimePeer ReviewedPostprint (published version

A web interface for meta-heuristics based grid schedulers

The use of meta-heuristics for designing efficient Grid schedulers is currently a common approach. One issue related to Grid based schedulers is their evaluation under different Grid configurations, such as dynamics of tasks and machines, task arrival, scheduling policies, etc. In this paper we present a web application that interfaces the final user with several meta-heuristics based Grid schedulers. The application interface facilities for each user the remote evaluation of the different heuristics, the configuration of the schedulers as well as the configuration of the Grid simulator under which the schedulers are run. The simulation results and traces are graphically represented and stored at the server and can retrieved in different formats such as spreadsheet form or pdf files. Historical executions are as well kept enabling a full study of use cases for different types of Grid schedulers. Thus, through this application the user can extract useful knowledge about the behavior of different schedulers by simulating realistic conditions of Grid system without needing to install and configure any specific software.Peer ReviewedPostprint (published version

Identifying experts in the field of visual arts using oculomotor signals

In this article, we aimed to present a system that enables identifying experts in the field of visual art based on oculographic data. The difference between the two classified groups of tested people concerns formal education. At first, regions of interest (ROI) were determined based on position of fixations on the viewed picture. For each ROI, a set of features (the number of fixations and their durations) was calculated that enabled distinguishing professionals from laymen. The developed system was tested for several dozen of users. We used k-nearest neighbors (k-NN) and support vector machine (SVM) classifiers for classification process. Classification results proved that it is possible to distinguish experts from non-experts

Efficient graph coloring with parallel genetic algorithms

In this paper a new parallel genetic algorithm for coloring graph vertices is presented. In the algorithm we apply a migration model of parallelism and define two new recombination operators SPPX and CEX. For comparison two problem{ oriented crossover operators UISX and GPX are selected. The performance of the algorithm is veri ed by computer experiments on a set of standard graph coloring instances

A Stackelberg game for modelling asymmetric users' behavior in grid scheduling

In traditional distributed computing the users and owners of the computational resources usually belong to the same administrative domain. Therefore all users are equally entitled to use the resources. The situation is completely different in large-scale emergent distributed computing systems, such as Grid systems, where the roles of the users are asymmetric as regards their access rights and usage of resources. Further, unlike traditional distributed computing case, Grid systems introduce hierarchical levels, which are to be taken into account for optimizing the overall system's performance. In this paper we present a Stackelberg game for modelling asymmetric users' behavior in Grid scheduling scenario. We define a two-level game with a Leader at the first level and the rest of users, called Followers, at the second one. The Leader is responsible for computing a planning of his tasks, which is usually a large fraction of the total pool of tasks in the batch. The Followers try to select the best strategy for the assignments of their tasks subject to Leader's strategy. The Stackelberg game is then translated into a hierarchical optimization problem, which is solved by Genetic Algorithm (GA) on the Leader's level and by ad hoc heuristic combined with GA on the Followers' level. We have experimentally evaluated the approach through a benchmark of static instances and report computational results for resource utilization, makespan and flowtimePeer Reviewe

A web interface for meta-heuristics based grid schedulers

The use of meta-heuristics for designing efficient Grid schedulers is currently a common approach. One issue related to Grid based schedulers is their evaluation under different Grid configurations, such as dynamics of tasks and machines, task arrival, scheduling policies, etc. In this paper we present a web application that interfaces the final user with several meta-heuristics based Grid schedulers. The application interface facilities for each user the remote evaluation of the different heuristics, the configuration of the schedulers as well as the configuration of the Grid simulator under which the schedulers are run. The simulation results and traces are graphically represented and stored at the server and can retrieved in different formats such as spreadsheet form or pdf files. Historical executions are as well kept enabling a full study of use cases for different types of Grid schedulers. Thus, through this application the user can extract useful knowledge about the behavior of different schedulers by simulating realistic conditions of Grid system without needing to install and configure any specific software.Peer Reviewe

Excitonic Interactions in Bacteriochlorin Homo-Dyads Enable Charge Transfer: A New Approach to the Artificial Photosynthetic Special Pair

Excitonically coupled bacteriochlorin (BC) dimers constitute a primary electron donor (special pair) in bacterial photosynthesis and absorbing units in light-harvesting antenna. However, the exact nature of the excited state of these dyads is still not fully understood. Here, we report a detailed spectroscopic and computational investigation of a series of symmetrical bacteriochlorin dimers, where the bacteriochlorins are connected either directly or by a phenylene bridge of variable length. The excited state of these dyads is quenched in high-dielectric solvents, which we attribute to photoinduced charge transfer. The mixing of charge transfer with the excitonic state causes accelerated (within 41 ps) decay of the excited state for the directly linked dyad, which is reduced by orders of magnitude with each additional phenyl ring separating the bacteriochlorins. These results highlight the origins of the excited-state dynamics in symmetric BC dyads and provide a new model for studying the primary processes in photosynthesis and for the development of artificial, biomimetic systems for solar energy conversion