7433683
Viral systems: A new bio-inspired optimisation approach
The paper presents a new approach to deal with combinatorial problems. It makes use of a biological analogy inspired by the performance of viruses. The replication mechanism, as well as the hosts' infection processes is used to generate a metaheuristic that allows the obtention of valuable results. The viral system (VS) theoretical context is described and it is applied to a library of medium-to-large-sized cases of the Steiner problem for which the optimal solution is known. The method is compared with the metaheuristics that have provided the best results for the Steiner problem. The VS provides better solutions than genetic algorithms and certain tabu search approaches. For the most sophisticated tabu search approaches (the best metaheuristic approximations to the Steiner problem solution) VS provides solutions of similar quality.
16750894
A Genetic Algorithm for Solving a Production and Delivery Scheduling Problem with Time Windows
This paper deals with the problem of selecting and scheduling a set of orders to be processed by a manufacturing plant and immediately delivered to the customer site. Constraints to be considered are the limited production capacity, the available number of vehicles and the time windows within which orders must be served. We describe the problem relating it to similar problems studied in the literature. A genetic algorithm to solve the problem is developed and tested empirically with randomly generated problems. Comparisons with an exact procedure and a tabu search procedure show that the method finds very good-quality solutions.
32057483
An Evolutionary Algorithm for the Design of Hybrid Fiber Optic-Coaxial Cable Networks in Small Urban Areas
Telecommunication is one of the fastest growing business sectors. Future networks will need to integrate a wide variety of services demanding different qualities and capacities from the network. In this paper, network architecture based on hybrid fiber optic-coaxial cable (HFC) is proposed to develop cable integrated telematic services. An evolutionary algorithm is presented to solve the problem in suitable computation times when dealing with real times civil works problems. Finally we present the results over both problem library and real life scenarios.
206167311
Genetic algorithm for planning cable telecommunication networks
Abstract Optical fiber networks over synchronous digital hierarchy operating on ATM mode appear as one of the best alternatives for the new high-speed telecommunications networks. The network management requires planning studies so that the designed networks allow efficient operation in real time. A quantitative model evaluating the global topological design of an optical fiber network over synchronous digital hierarchy is described. The model includes the economic aspects involved in the project, the civil works, the capacity evaluation costs and the introduction of reliability conditions. A genetic approach based on the exploitation of the Kuhn–Tucker optimality conditions is proposed to solve the model.
5708888
A new scalable directory architecture for large-scale multiprocessors
The memory overhead introduced by directories constitutes a major hurdle in the scalability of cc-NUMA architectures, which makes the shared-memory paradigm unfeasible for very large-scale systems. This work is focused on improving the scalability of shared-memory multiprocessors by significantly reducing the size of the directory. We propose multilayer clustering as an effective approach to reduce the directory-entry width. Detailed evaluation for 64 processors shows that using this approach we can drastically reduce the memory overhead, while suffering a performance degradation we similar to previous compressed schemes (such as Coarse Vector). In addition, a novel two-level directory architecture is proposed in order to eliminate the penalty caused by these compressed directories. This organization consists of a small Full-Map first-level directory (which provides precise information for the most recently referenced lines) and a compressed second-level directory (which provides in-excess information). Results show that a system with this directory architecture can achieve the same performance as a multiprocessor with a big and non-scalable Full-Map directory with a very significant reduction of the memory overhead.
17271240
DualFS: a new journaling file system without meta-data duplication
In this paper we introduce DualFS, a new high performance journaling file system that puts data and meta-data on different devices (usually, two partitions on the same disk or on different disks), and manages them in very different ways. Unlike other journaling file systems, DualFS has only one copy of every meta-data block. This copy is in the meta-data device, a log which is used by DualFS both to read and to write meta-data blocks. By avoiding a time-expensive extra copy of meta-data blocks, DualFS can achieve a good performance as compared to other journaling file systems. Indeed, we have implemented a DualFS prototype, which has been evaluated with microbenchmarks and macrobenchmarks, and we have found that DualFS greatly reduces the total I/O time taken by the file system in most cases (up to 97%), whereas it slightly increases the total I/O time only in a few and limited cases.
17489122
A scalable organization for distributed directories
Although directory-based cache-coherence protocols are the best choice when designing chip multiprocessors with tens of cores on-chip, the memory overhead introduced by the directory structure may not scale gracefully with the number of cores. Many approaches aimed at improving the scalability of directories have been proposed. However, they do not bring perfect scalability and usually reduce the directory memory overhead by compressing coherence information, which in turn results in extra unnecessary coherence messages and, therefore, wasted energy and some performance degradation. In this work, we present a distributed directory organization based on duplicate tags for tiled CMP architectures whose size is independent on the number of tiles of the system up to a certain number of tiles. We demonstrate that this number of tiles corresponds to the number of sets in the private caches. Additionally, we show that the area overhead of the proposed directory structure is 0.56% with respect to the on-chip data caches. Moreover, the proposed directory structure keeps the same information than a non-scalable full-map directory. Finally, we propose a mechanism that takes advantage of this directory organization to remove the network traffic caused by replacements. This mechanism reduces total traffic by 15% for a 16-core configuration compared to a traditional directory-based protocol.
14794164
Aspect-Oriented Programing Techniques to support Distribution, Fault Tolerance, and Load Balancing in the CORBA-LC Component Model
The design and implementation of distributed High Performance Computing (HPC) applications is becoming harder as the scale and number of distributed resources and application is growing. Programming abstractions, libraries and frameworks are needed to better overcome that complexity. Moreover, when Quality of Service (QoS) requirements such as load balancing, efficient resource usage and fault tolerance have to be met, the resulting code is harder to develop, maintain, and reuse, as the code for providing the QoS requirements gets normally mixed with the functionality code. Component Technology, on the other hand, allows a better modularity and reusability of applications and even a better support for the development of distributed applications, as those applications can be partitioned in terms of components installed and running (deployed) in the different hosts participating in the system. Components also have requirements in forms of the aforementioned non-functional aspects. In our approach, the code for ensuring these aspects can be automatically generated based on the requirements stated by components and applications, thus leveraging the component implementer of having to deal with these non-functional aspects. In this paper we present the characteristics and the convenience of the generated code for dealing with load balancing, distribution, and fault-tolerance aspects in the context of CORBA-LC. CORBA-LC is a lightweight distributed reflective component model based on CORBA that imposes a peer network model in which the whole network acts as a repository for managing and assigning the whole set of resources: components, CPU cycles, memory, etc.
12401146
Improving the performance of real-time communication services on high-speed LANs under topology changes
In this paper, we propose and evaluate a new protocol that provides topology change- and fault-tolerant real-time communication services on NOW and clusters. This protocol overcomes the main drawback of our previously proposed protocol, called Dynamically Re-established Real-Time Channels (DRRTC), which is physically limited by the number of virtual channels per port. The new protocol allows different real-time channels to share the same virtual channel. In this way, the new protocol allows us to establish a greater number of real-time channels than the previous one. Moreover, its only limitation is the bandwidth devoted to real-time traffic. However, this introduces two new problems that are successfully managed by the new protocol: the existence of cyclic dependencies among different real-time channels and the increased complexity of deadline requirements. We present and analyze the performance evaluation results when a single switch or a single link is deactivated/activated for different topologies and workloads. The new protocol overwhelms the DRRTC protocol while guaranteeing deadline requirements and channel recovery.