volving technology, has kept drawing a significant attention from both the computing industry and academia for nearly a decade.

No description available.

No description available.

No description available.

Numerous aspects of job scheduling in manufacturing systems have been the focus of several studies in the past decades. However, human factors in manufacturing systems such as workers’ mental conditions are still neglected issues and have not received adequate attentions. Job boredom and mental fatigue are both aspects of workers’ mental condition. They affect work performances by increasing sick leave duration and decreasing work productivity. On the other hand, job rotation could be an alternative strategy to cope with such human issues at work. The benefits of job rotation for both employees and firms have been widely recognized in the literature. Although some studies found job rotation as a means to reduce workers' physical work-related traumas, they did not consider the effect of variable mental conditions on workers. Despite the proven importance of boredom and mental fatigue at the workplace, they have not been a combined precise objective of any job rotation problem in current literature. The study of mental conditions proposed in this paper attempts to extend the previous works by addressing new methods and developing a feasible solution to increase manufacturing productivity. A new job scheduling program has been designed specifically which combines a new job rotation model and a job assignment method.

Numerous aspects of job scheduling in manufacturing systems have been the focus of several studies in the past decades. However, human factors in manufacturing systems such as workers’ mental conditions are still neglected issues and have not received adequate attentions. Job boredom and mental fatigue are both aspects of workers’ mental condition. They affect work performances by increasing sick leave duration and decreasing work productivity. On the other hand, job rotation could be an alternative strategy to cope with such human issues at work. The benefits of job rotation for both employees and firms have been widely recognized in the literature. Although some studies found job rotation as a means to reduce workers' physical work-related traumas, they did not consider the effect of variable mental conditions on workers. Despite the proven importance of boredom and mental fatigue at the workplace, they have not been a combined precise objective of any job rotation problem in current literature. The study of mental conditions proposed in this paper attempts to extend the previous works by addressing new methods and developing a feasible solution to increase manufacturing productivity. A new job scheduling program has been designed specifically which combines a new job rotation model and a job assignment method.

Τα τελευταία χρόνια η ραγδαία αύξηση της υπολογιστικής ισχύος, των αποθηκευτικών μέσων καθώς και των τηλεπικοινωνιών έχει δημιουργήσει γόνιμο έδαφος για την ανάπτυξη πολύπλοκων, απαιτητικών εφαρμογών, τόσο στον χώρο της επιστημονικής έρευνας, όσο και στα πλαίσια της παραγωγής εμπορικών λύσεων. Ως αποτέλεσμα αυτού, πραγματοποιείται μετάβαση από το μοντέλο των μεμονωμένων διακριτών πόρων στο μοντέλο της συνεργασίας κατανεμημένων πόρων το οποίο υλοποιείται από την τεχνολογία πλέγματος (Grid Computing). Ένα πολύ σημαντικό θέμα που επηρεάζει την συνολική απόδοση των δικτύων πλέγματος είναι η χρονοδρομολόγηση των εργασιών που υποβάλλουν οι χρήστες στους διαθέσιμους πόρους του δικτύου. Στόχος της παρούσας διπλωματικής εργασίας ήταν η μελέτη της χρονοδρομολόγησης στα δίκτυα πλέγματος όχι μέσω προγραμμάτων προσομοίωσης αλλά χρησιμοποιώντας το ενδιάμεσο λογισμικό gLite. Βασικό αντικείμενο μελέτης ήταν η υπηρεσία Workload Management System (WMS) στην οποία υλοποιούνται οι αλγόριθμοι χρονοπρογραμματισμού που παρέχει το gLite. Στόχος ήταν η ανάλυση της λειτουργίας των δύο αλγορίθμων χρονοπρογραμματισμού που παρέχει το ενδιάμεσο λογισμικό και η κατανόηση τόσο της αρχιτεκτονικής της WMS υπηρεσίας, που είναι μια από τις πιο σημαντικές για την λειτουργία ολόκληρου του δικτύου, αλλά και του τρόπου υλοποίησης των δύο αλγορίθμων του gLite. Στην συνέχεια προσθέσαμε στην υπηρεσία WMS ένα νέο δίκαιο αλγόριθμο ανάθεσης εργασιών στους διαθέσιμους πόρους του δικτύου πλέγματος. Τέλος αναπτύξαμε ένα μικρής κλίμακας δίκτυο πλέγματος για την πειραματική αξιολόγηση του νέου αλγορίθμου και την σύγκριση του με τους δύο βασικούς αλγορίθμους του gLite. Τα αποτελέσματα δείχνουν ότι ο αλγόριθμος μας παρέχει καλύτερη αξιοποίηση των πόρων του δικτύου, μειώνοντας παράλληλα το μέσο χρόνο εκτέλεσης μιας εργασίας στο δίκτυο. / The emergence of high speed optical networks is making the vision of Grids a reality. Grids consist of geographically distributed and heterogeneous computational and storage resources that may belong to different administrative domains, but can be shared among users by establishing global resource management architecture. An important issue in the performance of Grids is the scheduling of application tasks to the available resources. The Grid environment is quite dynamic, with resource availability and load varying rapidly with time, and application tasks have very different characteristics and requirements. Scheduling is a key to the success of Grid Networks, since it determines the efficiency in the use of the resources and the QoS provided to the users. In this work we present our experiences from implementing and integrating a new job scheduling algorithm in the gLite Grid middleware and present experimental results that compare it to the existing gLite scheduling algorithms. It is the first time that gLite scheduling algorithms are put under test and compared with a new algorithm under the same conditions. We describe the problems that were encountered and solved, going from theory and simulations to practice and the actual implementation of our fair scheduling algorithm. In this work we also describe the steps one needs to follow in order to develop and test a new scheduling algorithm in gLite. We present the methodology followed and the testbed set up for the comparisons. Our research sheds light on some of the problems of the existing gLite scheduling algorithms and makes clear the need for the development of new.

This work focuses on scheduling of MPI jobs when executing in shared-memory multiprocessors (SMPs). The objective was to obtain the best performance in response time in multiprogrammed multiprocessors systems using batch systems, assuming all the jobs have the same priority. To achieve that purpose, the benefits of supporting malleability on MPI jobs to reduce fragmentation and consequently improve the performance of the system were studied. The contributions made in this work can be summarized as follows:· Virtual malleability: A mechanism where a job is assigned a dynamic processor partition, where the number of processes is greater than the number of processors. The partition size is modified at runtime, according to external requirements such as the load of the system, by varying the multiprogramming level, making the job contend for resources with itself. In addition to this, a mechanism which decides at runtime if applying local or global process queues to an application depending on the load balancing between processes of it. · A job scheduling policy, that takes decisions such as how many processes to start with and the maximum multiprogramming degree based on the type and number of applications running and queued. Moreover, as soon as a job finishes execution and where there are queued jobs, this algorithm analyzes whether it is better to start execution of another job immediately or just wait until there are more resources available. · A new alternative to backfilling strategies for the problema of window execution time expiring. Virtual malleability is applied to the backfilled job, reducing its partition size but without aborting or suspending it as in traditional backfilling. The evaluation of this thesis has been done using a practical approach. All the proposals were implemented, modifying the three scheduling levels: queuing system, processor scheduler and runtime library. The impact of the contributions were studied under several types of workloads, varying machine utilization, communication and, balance degree of the applications, multiprogramming level, and job size. Results showed that it is possible to offer malleability over MPI jobs. An application obtained better performance when contending for the resources with itself than with other applications, especially in workloads with high machine utilization. Load imbalance was taken into account obtaining better performance if applying the right queue type to each application independently.The job scheduling policy proposed exploited virtual malleability by choosing at the beginning of execution some parameters like the number of processes and maximum multiprogramming level. It performed well under bursty workloads with low to medium machine utilizations. However as the load increases, virtual malleability was not enough. That is because, when the machine is heavily loaded, the jobs, once shrunk are not able to expand, so they must be executed all the time with a partition smaller than the job size, thus degrading performance. Thus, at this point the job scheduling policy concentrated just in moldability.Fragmentation was alleviated also by applying backfilling techniques to the job scheduling algorithm. Virtual malleability showed to be an interesting improvement in the window expiring problem. Backfilled jobs even on a smaller partition, can continue execution reducing memory swapping generated by aborts/suspensions In this way the queueing system is prevented from reinserting the backfilled job in the queue and re-executing it in the future.

Numerous aspects of job scheduling in manufacturing systems have been the focus of several studies in the past decades. However, human factors in manufacturing systems such as workers’ mental conditions are still neglected issues and have not received adequate attentions. Job boredom and mental fatigue are both aspects of workers’ mental condition. They affect work performances by increasing sick leave duration and decreasing work productivity. On the other hand, job rotation could be an alternative strategy to cope with such human issues at work. The benefits of job rotation for both employees and firms have been widely recognized in the literature. Although some studies found job rotation as a means to reduce workers' physical work-related traumas, they did not consider the effect of variable mental conditions on workers. Despite the proven importance of boredom and mental fatigue at the workplace, they have not been a combined precise objective of any job rotation problem in current literature. The study of mental conditions proposed in this paper attempts to extend the previous works by addressing new methods and developing a feasible solution to increase manufacturing productivity. A new job scheduling program has been designed specifically which combines a new job rotation model and a job assignment method.

Numerous aspects of job scheduling in manufacturing systems have been the focus of several studies in the past decades. However, human factors in manufacturing systems such as workers’ mental conditions are still neglected issues and have not received adequate attentions. Job boredom and mental fatigue are both aspects of workers’ mental condition. They affect work performances by increasing sick leave duration and decreasing work productivity. On the other hand, job rotation could be an alternative strategy to cope with such human issues at work. The benefits of job rotation for both employees and firms have been widely recognized in the literature. Although some studies found job rotation as a means to reduce workers' physical work-related traumas, they did not consider the effect of variable mental conditions on workers. Despite the proven importance of boredom and mental fatigue at the workplace, they have not been a combined precise objective of any job rotation problem in current literature. The study of mental conditions proposed in this paper attempts to extend the previous works by addressing new methods and developing a feasible solution to increase manufacturing productivity. A new job scheduling program has been designed specifically which combines a new job rotation model and a job assignment method.