Improvements in the performance of processors and networks means that it can be both feasible and interesting to treat collections of workstations, servers, clusters, and supercomputers as integrated computational resources or Grids. However, the highly heterogeneous and dynamic nature of such Grids makes application development extremely difficult. In this paper, we describe an architecture and prototype implementation for a Grid-enabled computational framework called Cactus-G. This framework integrates the Cactus simulation system with the MPICH-G2 Grid-enabled message passing library and in addition integrates a variety of specialized features to support efficient execution in Grid environments. In order to evaluate and demonstrate the effectiveness of this system, we are attempting a challenge computation involving a large astrophysics simulation distributed across multiple supercomputers at U.S. centers. In this extended abstract, we present preliminary results that suggest that this challenge computation is feasible; the final paper will present complete results
