The GENIE project has built a Grid-enabled Earth system modelling framework that facilitates the integration, execution and management of component models for the study of the Earth system over millennial timescales. The existing framework supports collaborative study of GENIE models across heterogeneous compute grids through scripted workflows in the Matlab environment. While the scripting approach achieves simplicity and flexibility, it suffers from an essentially passive approach to work unit management and from a heavy reliance on a central database to provide fault tolerance. The Windows Workflow Foundation (WF) technology provides a rich set of features to support the authoring and execution of workflows, tracking services that enable the monitoring of a running workflow, and state persistence services that allow workflows to be recovered and resumed upon failure. We demonstrate how the Windows Workflow Foundation has been applied to build a complementary simulation management system which provides rapid composition, event driven logic and reliable hosting of the scientific workflows while interfacing to existing infrastructure. We also describe how the adoption of WF enables the application of a number of associated technologies to provide better interoperability and accessibility for the simulation system. These improvements are demonstrated through a parametric study of the bi-stability of the oceanic thermohaline circulation in a GENIE model where the effects of a new carbon cycle are studied
Distributed shortestpathrouting algorithms based on the Ford-Fulkerson method are simple to implement but they suffer from the cost-dependent looping problem: when link costs increase, routing table loops may form and convergence to correct paths may be too slow, depending on link costs. This problem can be eliminated if constraints are imposed on the order in which routing tables are updated at different nodes but the resdting internode protocols tend to be relatively complex. Furthermore, update constraints may restrict a node's ability to obtain alternate paths quickly in an environment where topology changes are frequent. In this paper, a new distributed shortest-path routing scheme based on the Ford-Fulkerson method is presented. Under the new scheme, each node uses partial topology information to eliminate the cost-dependent looping problem. No update constraints are imposed and no assumptions are made regarding link costs. In the worst case, the new scheme responds to link cost changes in O(D) update steps, where D is the diameter of the network after the occurrence of the changes.
Abstract. The process of design search and optimisation is characterised by its computationally intensive operations, which produce a problem well suited to Grid computing. Here we present a Grid enabled computation toolkit that provides transparent and stable access to Grid compute resources from Matlab, which offers comprehensive support for the design optimisation processes. In particular, the access and integration of the Condor resource management system has been achieved by using the toolkit components that are enabled by Web service and service enhancement technologies. The use of the computation toolkit for a four-dimensional CFD parameter study with Matlab and Condor is considered as an exemplar problem.
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