T-system is a tool for parallel computing developed at the PSI RAS. The most recent implementation is available on both Linux and Windows platforms. The paper is dedicated to one of important T-system aspects — ability to change parallelism granule size at runtime. The technique is available, primarily, for recursive programs, but it’s possible to extent it to non-recursive ones as well. In the latter case, we employ C++ template“traits”for program transformation. The technique is shown to reduce overhead incurred by runtime support library dramatically. Key words: T-system, OpenTS, parallel programming, C++, computational clusters, parallel computing