MPI (Message Passing Interface) offers a suite of APIs for inter-process communication among parallel processes. We have approached to the acceleration of MPI collective communication such as MPI Bcast and MPI Allreduce, taking advantage of network programmability brought by Software Definned Networking (SDN). The basic idea is to allow a SDN controller to dynamically control the packet ows generated by MPI collective communication based on the communication pattern and the underlying network conditions. Al- Though our research have succeeded to accelerate an MPI collective communication in terms of execution time, the switching of network control functionality for MPI collec- Tive communication along MPI program execution have not been considered yet. This paper presents a mechanism that provides the control sequence for SDN controller to control packet ows based on the communication plan for the entire MPI application. The control sequence encloses a chronologically ordered list of the MPI collectives operated in the MPI application and the process-related information of each in the list. To verify if the SDN-enhanced MPI collectives can be used in combination with the proposed mechanism, the envisioned environment was prototyped. As a result, SDN-enhanced MPI collectives were able to be used in com-bination.
