Hypercube algorithms on mesh connected multicomputers

A new methodology named CALMANT (CC-cube Algorithms on Meshes and Tori) for mapping a type of algorithm that we call CC-cube algorithm onto multicomputers with hypercube, mesh, or torus interconnection topology is proposed. This methodology is suitable when the initial problem can be expressed as a set of processes that communicate through a hypercube topology (a CC-cube algorithm). There are many important algorithms that fit into the CC-cube type. CALMANT is based on three different techniques: (a) the standard embedding to assign the processes of the algorithm to the nodes of the mesh multicomputer; (b) the communication pipelining technique to increase the level of communication parallelism inherent in the CC-cube algorithms; and (c) optimal message-scheduling algorithms proposed in this work in order to avoid conflicts and minimizing in this way the communication time. Although CALMANT is proposed for multicomputers with different interconnection network topologies, the paper only focuses on the particular case of meshes.Peer ReviewedPostprint (published version

A study of the communication cost of the FFT on torus multicomputers

The computation of a one-dimensional FFT on a c-dimensional torus multicomputer is analyzed. Different approaches are proposed which differ in the way they use the interconnection network. The first approach is based on the multidimensional index mapping technique for the FFT computation. The second approach starts from a hypercube algorithm and then embeds the hypercube onto the torus. The third approach reduces the communication cost of the hypercube algorithm by pipelining the communication operations. A novel methodology to pipeline the communication operations on a torus is proposed. Analytical models are presented to compare the different approaches. This comparison study shows that the best approach depends on the number of dimensions of the torus and the communication start-up and transfer times. The analytical models allow us to select the most efficient approach for the available machine.Peer ReviewedPostprint (published version

Active yellow pages: a pipelined resource management architecture for wide-area network computing

This paper describes a novel, pipelined resource management architecture for computational grids. The design is based on two key realizations. One is that resource management involves a sequence of tasks that is best handled by a pipeline. As shown in the paper, this approach results, in a scalable architecture for decentralized scheduling. The other realization is that static aggregation of resources for improved scheduling is inadequate in wide-area computing environments because the needs of users and jobs change with both, location and time. The described architecture addresses this problem by dynamically aggregating resources in a manner that continuously optimizes system response. This is accomplished by way of an active yellow pages directory that allows aggregation constraints to be (re)defined on the fly. An initial prototype of the active yellow pages service has been deployed in the PUNCH network computing environment. Experiences with the production PUNCH system and preliminary results from controlled experiments indicate that the active yellow pages service performs well.Peer Reviewe

ULabGrid, an infrastructure to develop distant laboratories for undergrad students over a Grid

Nowadays, there is a big discussion about two different topics: how distance learning and the old fashioned learning can be improved using the new technologies. In both cases, there are many collaborative tools based on the web infrastructure such as e-mail, web discussing groups, virtual campuses or audio and video conferences, that basically give a way of exchanging information among the different groups involved in learning tasks, but very few of them have been thought to help or to develop laboratory classes (labs). In this paper we describe a GRID infrastructure (ULabGrid) that supports distant laboratories for undergrad students.Peer Reviewe

Decentralized vs. centralized economic coordination of resource allocation in grids

Application layer networks are software architectures that allow the provisioning of services requiring a huge amount of resources by connecting large numbers of individual computers, like in Grid or Peer-to-Peer computing. Controlling the resource allocation in those networks is nearly impossible using a centralized arbitrator. The network simulation project CATNET will evaluate a decentralized mechanism for resource allocation, which is based on the economic paradigm of the Catallaxy, against a centralized mechanism using an arbitrator object. In both versions, software agents buy and sell network services and resources to and from each other. The economic model is based on self-interested maximization of utility and self-interested cooperation between agents. This article describes the setup of money and message flows both for centralized and decentralized coordination in comparison.Peer Reviewe

Experiencia de aprendizaje cooperativo con una herramienta de colaboración síncrona y ordenadores portátiles

El aprendizaje cooperativo puede facilitarse o hacerse posible con la mediación de aplicaciones informáticas de soporte a la cooperación y/o con ordenadores portátiles usando redes inalámbricas. En este trabajo se presenta una experiencia inicial que se ha realizado en un centro universitario, la EPSC, en que se ha utilizado una herramienta de colaboración síncrona llamada EdebeNet, para dar soporte a la colaboración en una clase con estudiantes universitarios de primer ciclo, utilizando PC en red fijos y portátiles con red inalámbrica. Se describe el diseño de la actividad, el mapeo con la funcionalidad de la aplicación, el desarrollo y una evaluación de la experiencia con un grupo de estudiantes utilizando la herramienta y otro grupo de control. Finalmente se valoran los resultados obtenidos y las lecciones aprendidas

Experiencia de aprendizaje cooperativo con una herramienta de colaboración síncrona y ordenadores portátiles

El aprendizaje cooperativo puede facilitarse o hacerse posible con la mediación de aplicaciones informáticas de soporte a la cooperación y/o con ordenadores portátiles usando redes inalámbricas. En este trabajo se presenta una experiencia inicial que se ha realizado en un centro universitario, la EPSC, en que se ha utilizado una herramienta de colaboración síncrona llamada EdebeNet, para dar soporte a la colaboración en una clase con estudiantes universitarios de primer ciclo, utilizando PC en red fijos y portátiles con red inalámbrica. Se describe el diseño de la actividad, el mapeo con la funcionalidad de la aplicación, el desarrollo y una evaluación de la experiencia con un grupo de estudiantes utilizando la herramienta y otro grupo de control. Finalmente se valoran los resultados obtenidos y las lecciones aprendidas.Postprint (published version

Experiencia de aprendizaje cooperativo con una herramienta de colaboración síncrona y ordenadores portátiles

El aprendizaje cooperativo puede facilitarse o hacerse posible con la mediación de aplicaciones informáticas de soporte a la cooperación y/o con ordenadores portátiles usando redes inalámbricas. En este trabajo se presenta una experiencia inicial que se ha realizado en un centro universitario, la EPSC, en que se ha utilizado una herramienta de colaboración síncrona llamada EdebeNet, para dar soporte a la colaboración en una clase con estudiantes universitarios de primer ciclo, utilizando PC en red fijos y portátiles con red inalámbrica. Se describe el diseño de la actividad, el mapeo con la funcionalidad de la aplicación, el desarrollo y una evaluación de la experiencia con un grupo de estudiantes utilizando la herramienta y otro grupo de control. Finalmente se valoran los resultados obtenidos y las lecciones aprendidas

Executing algorithms with hypercube topology on torus multicomputers

Many parallel algorithms use hypercubes as the communication topology among their processes. When such algorithms are executed on hypercube multicomputers the communication cost is kept minimum since processes can be allocated to processors in such a way that only communication between neighbor processors is required. However, the scalability of hypercube multicomputers is constrained by the fact that the interconnection cost-per-node increases with the total number of nodes. From scalability point of view, meshes and toruses are more interesting classes of interconnection topologies. This paper focuses on the execution of algorithms with hypercube communication topology on multicomputers with mesh or torus interconnection topologies. The proposed approach is based on looking at different embeddings of hypercube graphs onto mesh or torus graphs. The paper concentrates on toruses since an already known embedding, which is called standard embedding, is optimal for meshes. In this paper, an embedding of hypercubes onto toruses of any given dimension is proposed. This novel embedding is called xor embedding. The paper presents a set of performance figures for both the standard and the xor embeddings and shows that the latter outperforms the former for any torus. In addition, it is proven that for a one-dimensional torus (a ring) the xor embedding is optimal in the sense that it minimizes the execution time of a class of parallel algorithms with hypercube topology. This class of algorithms is frequently found in real applications, such as FFT and some class of sorting algorithms.Peer Reviewe

Executing algorithms with hypercube topology on torus multicomputers

Many parallel algorithms use hypercubes as the communication topology among their processes. When such algorithms are executed on hypercube multicomputers the communication cost is kept minimum since processes can be allocated to processors in such a way that only communication between neighbor processors is required. However, the scalability of hypercube multicomputers is constrained by the fact that the interconnection cost-per-node increases with the total number of nodes. From scalability point of view, meshes and toruses are more interesting classes of interconnection topologies. This paper focuses on the execution of algorithms with hypercube communication topology on multicomputers with mesh or torus interconnection topologies. The proposed approach is based on looking at different embeddings of hypercube graphs onto mesh or torus graphs. The paper concentrates on toruses since an already known embedding, which is called standard embedding, is optimal for meshes. In this paper, an embedding of hypercubes onto toruses of any given dimension is proposed. This novel embedding is called xor embedding. The paper presents a set of performance figures for both the standard and the xor embeddings and shows that the latter outperforms the former for any torus. In addition, it is proven that for a one-dimensional torus (a ring) the xor embedding is optimal in the sense that it minimizes the execution time of a class of parallel algorithms with hypercube topology. This class of algorithms is frequently found in real applications, such as FFT and some class of sorting algorithms.Peer Reviewe