Recent Advances in the Message Passing Interface

Volume 6305 of the series Lecture Notes in Computer Science pp 31-41

PMI: A Scalable Parallel Process-Management Interface for Extreme-Scale Systems

  • Pavan BalajiAffiliated withArgonne National Laboratory
  • , Darius BuntinasAffiliated withArgonne National Laboratory
  • , David GoodellAffiliated withArgonne National Laboratory
  • , William GroppAffiliated withUniversity of Illinois
  • , Jayesh KrishnaAffiliated withArgonne National Laboratory
  • , Ewing LuskAffiliated withArgonne National Laboratory
  • , Rajeev ThakurAffiliated withArgonne National Laboratory

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Parallel programming models on large-scale systems require a scalable system for managing the processes that make up the execution of a parallel program. The process-management system must be able to launch millions of processes quickly when starting a parallel program and must provide mechanisms for the processes to exchange the information needed to enable them communicate with each other. MPICH2 and its derivatives achieve this functionality through a carefully defined interface, called PMI, that allows different process managers to interact with the MPI library in a standardized way. In this paper, we describe the features and capabilities of PMI. We describe both PMI-1, the current generation of PMI used in MPICH2 and all its derivatives, as well as PMI-2, the second-generation of PMI that eliminates various shortcomings in PMI-1. Together with the interface itself, we also describe a reference implementation for both PMI-1 and PMI-2 in a new process-management framework within MPICH2, called Hydra, and compare their performance in running MPI jobs with thousands of processes.