Swift/T: Dataflow Composition of Tcl Scripts for Petascale Computing

We present Swift/T, a novel programming language for extreme-scale supercomputers, that compiles into Tcl code for execution on a runtime based on Tcl and MPI. The Swift/T language enables users to rapidly compose Tcl fragments, including Tcl extension functions implemented in native code, into a massively scalable program capable of utilizing petaflop-scale computers. Swift/T has a growing user community in multiple scientific computing domains, including materials science, proteomics, and epidemiology. This paper summarizes the use of Swift/T for Tcl users, its performance achievements, and some early use cases.