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Published byEdgar Watts Modified over 9 years ago
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Astrophysical Applications on Superclusters Matthew Bailes Swinburne Centre for Astrophysics and Supercomputing
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Outline No: –Linpack Mflops –latencies –bandwidths –evangelism Why a Supercluster? What is the Supercluster? How do we use the Supercluster? What does it do?
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Why a Supercluster? Swinburne wants reputation. Hypothesis: –30 times the power –Six years of Moore’s law We can do problems 30x as complex as other groups.
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Centre Goals: Fundamental Research. Public Outreach and Education. Commercial Supercomputing. –Astrophysical Special Effects –Cluster Monitoring Tools –Commercial Rendering
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What is the Supercluster? Supercluster sounds better than Beowulf if you are an astronomer. Design Goals SSI I (1998): –No one component worth more than A10K –Order of magnitude more than single workstation. –Dedicated resource. (dispel various myths) –10 GB scratch/node. –10 MB/s IO node-node. –Decent fortran/C/C++ compiler.
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Case Study: CSIRO Astronomy 1984: VAX 11/780 1989: Convex C2 ( > 10 times speed up) 1995: Power Challenge ( 10 processors ) 1999: Linux Boxes Unless package supports parallelism, users won’t use clusters or even SMP/Numa unless their science is obviously constrained.
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Theorists: Possess and use clusters effectively. Know what MPI is. Can’t get money.
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SSI I (Jan 1998) 16 DEC 500 MHz alphas 2MB cache 192 MB RAM 13 GB disk 24-port CISCO switch MPICH/f77/C++/FFTw/emacs/gcc Zeroeth Law of Cluster Computing: Cluster Computing is inevitable if your budget is finite.
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SSI II (Nov 1998). SSI I + 8 x 600 MHz DECs 4 MB cache. Corollary: Your first cluster is your happiest. First Law of Cluster Computing: Your cluster soon becomes hetereogeneous.
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SSI III (March 1999) SSI II + –41 500 MHz ev6 processors –512 MB RAM/node –18 GB disk/node CISCO 5500 switch –3.2 Gb/s backplane Virtual Reality Theatrette –Seats 37 Second Law of Cluster Computing: MTBF = MTBF 0 /N
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How do we use the Supercluster? Linux Workstations. (despite free OS) No batch system (just 3 “power” users). Home-grown MPI programs. C++/fortran/java.
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Problems: Distributed TB disk rarely has > 10% free. MPI hangs on FPE or “p4pg” errors. CPUs too powerful for fast ethernet and tape drive on some applications. Difficult to monitor.
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Applications. Neutron Star Searches. –Looked at 10% of the Southern Sky –Recorded 1.4 TB in 21 days. –1 ev56 workstation take 7 years. –SSI III took 25 days. Discovered 7 “millisecond” pulsars. –Could scale to 1000 nodes on TCP/IP. 17 MB256MBFFTSearchFoldSave
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Discovery Implications: Discovered most relativistic Neutron Star + white dwarf binary known. Emit gravitational waves –Coalesce in 7 Gyr. Population of ultra- relativistic systems.
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Problems. Most interesting systems are relativistic. Full sensitivity requires coherent addition. If observation time > 10 minutes, computational penalty becomes very large.
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Coherent Dedispersion. Problem: –Cosmic Signals are Weak –Cosmic radio signals propagate at v!=c In 1971 new method proposed: –record electric field –Apply numerical filter to it.
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What does this mean? 20 MHz = 20 MB/second. 200 times real time to process (ev6) Gives 50 nanosecond time resolution Need 7*8 hour observations to do science –One node 1.5 yr –50 nodes 9 days –1985 VAX 11/780 (one century)
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Discovered? Millisecond pulsars emit short (1us wide) pulses across GHz bandwidths –Implies seed areas of 30 cm or less PSR 0437-4715 in a 5.7 day orbit –1 Mkm in radius a-b = 180.1 mm a b
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Future: Search for us wide pulses in SN 1987A –25 day search HIPASS - 600 GB in < 12 hours. SSI III + servernet can mimic CSIRO’s correlator SSI IV: –ES40 + TB disk SSI V: –128 nodes + Inifiniband/servernet II?
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Conclusions: Clusters are too hard to code for most astronomers. MPIwhat? Breakthroughs are possible with radical increases in computer power.
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www.swin.edu.au/astronomy
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