An orchestration language for parallel objects

Charm++, a parallel object language based on the idea of virtual processors, has attained significant success in effi-cient parallelization of applications. Requiring the user to only decompose the computation into a large number of ob-jects (“virtual processors ” or VPs), Charm++ empowers its intelligent adaptive runtime system to assign and reassign the objects to processors at runtime. This facility is used to optimize execution, including via dynamic load balancing. Having multiple sets of VPs for distinct parts of a simulation leads to improved modularity and performance. However, it also tends to obscure the global flow of control: One must look at the code of multiple objects to discern how the sets of objects are orchestrated in a given application. In this paper, we present an orchestration notation that allows ex-pression of Charm++ functionality without its fragmented flow of control. 1