U.S. Department of Energy’s Office of Science High Performance Computing Challenges and Opportunities Dr. Daniel Hitchcock 12/5/2005

Office of Science U.S. Department of Energy 2 Why is high performance computing hard?  Amdahl’s Law (No Free Lunch)  Moore’s Law (Even when you think there’s a free lunch there isn’t)  Software Complexity

Office of Science U.S. Department of Energy 3 Amdahl’s Law The time needed to complete a task is about the same as the sum of the times required to complete the subtasks. T ~ T cpu + T comm + T i/o T ~ T mesh + T comp + T interpret T ~ T growth + T exp + T analysis

Office of Science U.S. Department of Energy 4 Moore’s Law The number of transistors on an integrated circuit doubles about every 2 years.  A business principle not a law of nature!  Contributes to but not directly responsible for increases in performance!  In combination with Amdahl yields increased software complexity!  Memory slower than CPU’s  I/O slower than memory

Office of Science U.S. Department of Energy 5 CPU Performance  Increases in clock rate but power goes as square of frequency.  Multiple instructions per clock cycle.  Memory management  Caches  Pin management Clock rate increases are expected to slow and all chips will go to 4 or more cpu’s by 2010.

Office of Science U.S. Department of Energy 6 Computer Architecture Primer Computers are like cities! Vector Interface Serial Interface CPU Cache Interconnection Network

Office of Science U.S. Department of Energy 7 It’s all so complicated, maybe I’ll just go infect someone Stop Complaining! Plague…You won’t catch me from computer scientists or mathematicians I’m way more dangerous than either of you or them! If I get to them first there’ll be no flesh to infect!!! What does this have to do with biology?

Office of Science U.S. Department of Energy 8 Software and Hardware Complexity  The desktop of 2010 will have 4-8 processors.  Today’s 64 processor clusters will have over 500 processors  Petascale systems may have hundreds of thousands of processors.  How to divide up the work  Dealing with hardware failure  Managing the software  Enabling science

Office of Science U.S. Department of Energy 9 How to Succeed in High Performance Computing without really dying…  Never forget Amdahl  Remember Willy Sutton (Go where the money is.)  The least expensive piece of software to develop is the one you can use from someone else.  Use wetware…Collaborate

Office of Science U.S. Department of Energy 10 SciDAC Wetware for Scientific Discovery Computers and Networks Integrated Software Infrastructure Centers (ISICs) Collaboratory Tools & Middleware Scientific Application Partnerships Collaboratory Pilot Projects Scientific Teams ASCR BES, BER, FES, HEP, NP I love Wetware!!!