Katarzyna Rycerz

Workflow composer and service registry for grid applications

Automatic composition of workflows from Web and Grid services is an important challenge in todays distributed applications. The system presented in this paper supports the user in composing an application workflow from existing Grid services. The flow composition system builds workflows on an abstract level with semantic and syntactic descriptions of services available on the Grid. Two main modules of the system are the flow composer and the distributed Grid service registry. We present motivation, the concept of the overall system architecture and the results of a feasibility study.

A Framework for HLA-Based Interactive Simulations on the Grid

This article presents the design and feasibility of a system that supports execution of High Level Architecture (HLA)-distributed interactive simulations in an unreliable Grid environment. The article presents an overall architecture of a system based on experience gained from previous designs. The most important operational components of the system are presented, and actual performance issues are discussed. The design of the architecture is based on the Open Grid Services Architecture (OGSA) concept that allows for modularity and compatibility with Grid services already being developed. The issue of migration to the recently proposed Web Services Resource Framework (WSRF) is discussed as well.

A distributed multiscale computation of a tightly coupled model using the Multiscale Modeling Language

Abstract Nature is observed at all scales; with multiscale modeling, scientists bring together several scales for a holistic analysis of a phenomenon. The models on these different scales may require significant but also heterogeneous computational resources, creating the need for distributed multiscale computing. A particularly demanding type of multiscale models, tightly coupled, brings with it a number of theoretical and practical issues. In this contribution, a tightly coupled model of in-stent restenosis is first theoretically examined for its multiscale merits using the Multiscale Modeling Language (MML); this is aided by a toolchain consisting of MAPPER Memory (MaMe), the Multiscale Application Designer (MAD), and Gridspace Experiment Workbench. It is implemented and executed with the general Multiscale Coupling Library and Environment (MUSCLE). Finally, it is scheduled amongst heterogeneous infrastructures using the QCG-Broker. This marks the first occasion that a tightly coupled application uses distributed multiscale computing in such a general way.

Distributed Multiscale Computations Using the MAPPER Framework

We present a global overview of the methodology developed within the MAPPER European project to design, implement and run a multiscale simulation on a distributed supercomputing infrastructure. Our goal is to highlight the main steps required when developing an application within this framework. More specifically, we illustrate the proposed approach in the case of hydrology applications. A performance model describing the execution time of the application as a function of its spatial resolution and the hardware performance is proposed. It shows that Distributed Multiscal Computation is beneficial for large scale problems.

Semantic-Based grid workflow composition

The work presents a solution to abstract workflow composition in a semantic Grid environment. Along with analysis of the problem of workflow composition and the description of related research in that matter, we present the Workflow Composition Tool. The tool is designed to provide descriptions of abstract (i.e. not executable) workflows of service-based Grid applications. The tool applies novel semantic techniques to deliver meaningful discovery and matching of ontologically described resources. WCT is a part of larger workflow composition and execution system being developed in the K-WfGrid project – the short description of the entire system is also included.

Regular Paper: Interactive N-Body Simulations On the Grid: HLA Versus MPI

The grid paradigm for distributed computation provides an interesting framework for the simulation of dense stellar systems, which remains a great challenge for astrophysicists. In this work we apply a distributed simulation model to the astrophysical N-body problem: the High Level Architecture (HLA), using distributed federations on top of grid infrastructures for the communication between simulation and visualization components. To achieve this goal, we use a grid HLA Management system (G-HLAM) for HLA-based simulations running on the grid. We compare this setup with a direct parallelization of the N-body code using MPI on the grid. Our aim is to provide scientists with an interactive environment where, in contrast to traditional MPI-based parallel processing, seamless simulation process migration and rollbacks can be invoked on the fly to improve the overall computational performance. We found that MPI and HLA are complementary rather than competing technologies, as they can be used simultaneously to improve the performance of complex simulations on different fronts. On one hand, if the communication to computation ratio is small enough, the MPI parallelization proves to be a relatively easy and efficient method for taking advantage of grid technology. On the other hand, HLA provides advanced mechanisms to synchronize simulation and visualization components located on different grid nodes and can be used to add steering mechanisms to improve interaction. Finally, we found that HLA allows migration of running simulations to be easily managed, reducing overall communication times between simulation and the user, effectively improving the overall system performance.

Support for Effective and Fault Tolerant Execution of HLA-Based Applications in the OGSA Framework

The execution of High Level Architecture (HLA) distributed interactive simulations in an unreliable Grid environment requires efficient brokering of resources, which is an important part of the Grid Services framework supporting execution of such simulations. This paper presents the overall architecture of the framework with emphasis on services supplying the Broker Service with information about application performance on a Wide Area Network (WAN). For that purpose, a benchmark interaction-simulation-visualization schema is designed basing on CrossGrid medical application architecture [1,10].

Composing, execution and sharing of multiscale applications

This paper presents the research which led to elaboration of an environment for composing, executing and sharing multiscale applications. The resulted environment supports ability to connect software modules to form large-scale, multiscale simulations and directly execute them on distributed e-infrastructures suitable for particular application models chosen by users. It also enables hybrid execution, i.e. different parts of the same application can be executed on various types of e-infrastructures i.e. on a grid (e.g. EGI), HPC (e.g. PRACE) or on a cloud. The environment is web based and gives the user a direct access to the distributed resources from a single browser. It supports a variety of possible realizations of multiscale simulations in a unified and non-invasive way and enables storing model metadata such as scale, inputs and outputs.The presented environment consists of an application composition tool called Multiscale Application Designer (MAD), an application module description registry MAPPER Memory (MaMe) and GridSpace (GS) supporting execution of applications on various infrastructures. We present an architecture of the current implementation along with a detailed description of the tools and their current features. Additionally, we report on validation of our tools by multiscale application developers. We compare the processes of creating and running applications with and without the tools and we present a case study based on a sample multiscale application skeleton. Environment supporting composition and sharing of multiscale applications.Direct execution of multiscale applications on distributed e-infrastructures.Support for hybrid execution on different types of e-infrastructures.Support for a variety of realizations of multiscale simulations in a non-invasive way.Validation by multiscale application developers.

Support for Multiscale Simulations with Molecular Dynamics

We present a reusable solution that supports users in combining single-scale models to create a multiscale application. Our approach applies several multiscale programming tools to allow users to compose multiscale applications using a graphical interface, and provides an easy way to execute these multiscale applications on international production infrastructures. Our solution extends the general purpose scripting approach of the GridSpace platform with simple mechanisms for accessing production resources, provided by the Application Hosting Environment (AHE). We apply our support solution to construct and execute a multiscale simulation of clay-polymer nanocomposite materials, and showcase its benefit in reducing the effort required to do a number of time-intensive user tasks.

Problem solving environment for distributed interactive applications

Interactive Problem Solving Environments (PSEs) offer an integrated approach for constructing and running complex systems, such as distributed simulation systems. To achieve efficient execution of High Level Architecture (HLA)-based distributed interactive simulations on the Grid, we introduce a PSE called Grid HLA Management System (G-HLAM) for their management. This is done by introducing migration and monitoring mechanisms for such applications. In this paper we present how G-HLAM can be applied to the applications supporting surgeons with simulations of vascular reconstruction, using distributed federations on the Grid for the communication among simulation and visualization components.