1. A computer program product comprising a tangible computer readable recordable storage memory including computer useable program code for implementing a workflow, the computer program product including: computer useable program code for merging a workflow to create a virtual graph, wherein the workflow comprises two or more directed acyclic graphs (DAGs), wherein said merging comprises: applying a label to each node of the two or more directed acyclic graphs, wherein nodes representing a same computation in each directed acyclic graph have a same label applied thereto; assigning each node in the two or more directed acyclic graphs with a unique label to a unique node in the virtual graph; and assigning each node in the two or more directed acyclic graphs that shares the same label with one or more additional nodes are assigned to a same node in the virtual graph; computer useable program code for mapping each of one or more nodes of the virtual graph to one or more physical nodes; and computer useable program code for using a message passing scheme to implement a computation via the one or more physical nodes.