Center for Programming Models for Scalable Parallel Computing: Project Meeting Report Libraries, Languages, and Execution Models for Terascale Applications William D. Gropp Argonne National Laboratory

Center for Programming Models for Scalable Parallel Computing2 Participants Coordinating Principal Investigator: Ewing Lusk – Argonne National Laboratory Co-Principal Investigators (Laboratories): William Gropp – Argonne National Laboratory Ricky Kendall – Ames Laboratory Jarek Nieplocha – Pacific Northwest National Laboratory Co-Principal Investigators (Universities): Barbara Chapman – University of Houston Guang Gao – University of Delaware John Mellor-Crummey – Rice University Robert Numrich – University of Minnesota Dhabaleswar Panda – Ohio State University Thomas Sterling – California Institute of Technology Marianne Winslett – University of Illinois Katherine Yelick – University of California, Berkeley

Center for Programming Models for Scalable Parallel Computing3 Problem Statement Problem: Current programming models have enabled development of scalable applications on current large-scale computers, but the application development process itself remains complex, lengthy, and expensive, obstructing progress in scientific application development. Solution: Facilitate application development by providing standard libraries, convenient parallel programming languages, and petaflops-targeted advanced programming models. Goals: An array of attractive options for convenient, efficient, development of scalable, efficient scientific applications for terascale computers

Center for Programming Models for Scalable Parallel Computing4 A Three-Pronged Approach to Next- Generation Programming Models Extensions to existing library-based models MPI (-2; extensions) Global Arrays and extensions Portable SHMEM Robust implementations of language-based models UPC Co-Array Fortran Titanium OpenMP optimizations Advanced models for advanced architectures Multithreaded, PIM-based machines, Gilgamesh, etc.

Center for Programming Models for Scalable Parallel Computing5 Relationships Among the Parts Message Passing Remote Memory Shared Memory Mixed Models Language Extensions New Models Application Programming ModelsCommunication Firmware VIAMyrinetInfiniband MPP Switches Model Instances EARTHTitaniumGPSHMEMGAMPI-2MPIUPCCAFOpenMP + MPI OpenMP Implementation Substrate Panda Parallel I/OCAF Packages/ Modules Common Runtime ARMCIADI-3 Open64 Compiler HDF-5

Center for Programming Models for Scalable Parallel Computing6 Libraries Libraries for the remote memory access model MPI and MPI-2 Global Arrays GA combine higher-level model with efficiency for application convenience GP-SHMEM Popular Cray T3E model made portable Co-Array Fortran library Object-based scientific library, written in CAF

Center for Programming Models for Scalable Parallel Computing7 Languages Three languages providing a software global address space (suitable for distributed memory) and parallelism CAF (Co-Array Fortran) UPC (Unified Parallel C) Titanium (parallel Java) One language for shared memory Scalable OpenMP The Open64 compiler infrastructure Industrial strength compiler for C, Fortran 9x, C++ Used in the above projects One contribution to the community

Center for Programming Models for Scalable Parallel Computing8 Cross-Project Infrastructure Runtime communication approaches Exploiting NICs in support of parallel programming models ARMCI GASNet I/O Active buffering in Panda MPI-IO and parallel file systems Integrating active buffering into ROMIO implementation of MPI-IO Scalable I/O for parallel languages UPC CAF I/O

Center for Programming Models for Scalable Parallel Computing9 New Programming Models Defining a new execution model Semantics first Define for performance –Must provide the enormous benefit Bill Camp mentioned Define to support best algorithms in support of applications Define for likely HPC hardware, including –Many (zillions) processors –Deep memory hierarchy –Some hardware support for programming model Likely to have some kind of precisely relaxed memory consistency model –Common feature of all of the high performance libraries and languages in the project (even OpenMP) Experiments with new concepts such as percolation (move program to data instead of data to program)

Center for Programming Models for Scalable Parallel Computing10 Connections With Other Programs Applications from SciDAC, NSF/PACI, etc. DARPA HPCS Program John Mellor-Crummey (Rice) for HP Bob Numrich (UMN) for SGI Thomas Sterling (JPL/Caltech) for Cray Kathy Yelick (Berkeley) for SUN Guang Gao (U Delaware) IBM ANL a member of Cray Affiliates program Open64 Community OpenMP (U Houston formed a company to join ARB, since only companies can be members  ) IBM Blue Gene/L and QCDoC More…