Swift/T is a language for high-performance computing. Swift code is compiled into a Tcl program that uses the Turbine (hence, /T) and ADLB (Asynchronous Dynamic Load Balancer) runtime libraries loaded into a Tcl interpreter for highly scalable dataflow processing over MPI, without single-node bottlenecks.
Swift is a naturally concurrent language with C-like syntax. It is primarily used to manage calls to leaf tasks- external functions written in C, C++, Fortran, Python, R, Tcl, or executable programs. The Swift language coordinates the distribution of data to these tasks and schedules them for concurrent execution across the nodes of a large system.
Swift/T was developed as part of the ExM project. ExM is a collaborative project, led by Argonne National Laboratory, with University of Chicago and University of British Columbia.
See paper: Petascale Tcl with NAMD, VMD, and Swift/T