Cs591x cluster computing
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CS591x Cluster Computing. Interconnect Performance. Interconnect Performance. Major factor in computational performance… For communication intensive applications – collaborative processes Less important for compute intensive/low communications applications.

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CS591x Cluster Computing

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Cs591x cluster computing

CS591x Cluster Computing

Interconnect Performance


Interconnect performance

Interconnect Performance

  • Major factor in computational performance…

  • For communication intensive applications – collaborative processes

  • Less important for compute intensive/low communications applications


Comparison of interconnect technology estimates

Comparison of Interconnect Technology -estimates


Others

Others

  • 10 GigE

    • Coming along

    • Still expensive

  • Cray RapidArray Interconnect - XD1

    • 9 Gbs bandwidth

    • 1.8 us latency

    • Low overhead


Interconnect summary

Interconnect summary

  • Fast Ethernet cheap, poor performance

  • GigE – getting cheaper, better bandwidth, latency and overhead problems

  • Myrinet, Quadrics – very good bandwidth, low latency, low overhead – expensive – likely to stay expensive


Interconnect summary1

… Interconnect Summary

  • 10 GigE is coming along – too early to tell

  • Infiniband is the technology to watch

    • Very good performance

    • Expensive, but getting cheaper

  • Custom “Fabrics”

    • Very high performance

    • Cray XD1


Interconnect

Interconnect

  • Performance influenced by transport protocol (i.e. IP)

  • Shared memory for communication results in better performance, but may have other problems

  • Application design may be tuned for particular interconnect architecture


Compiling programs on energy

Compiling Programs on energy

  • C/C++Compilers

    • gcc/g++

    • icc

    • pgcc/pgCC

    • mpicc, mpiCC


Compiling programs on energy1

Compiling Programs on energy

  • Fortran Compilers

    • gcc/g77

      • Fortran 77 (maybe more coming)

      • Gcc recognizes file extension (.f, .for,…)

    • Ifort - Intel Fortran 95

    • mpif77

    • pgf77

    • pgf90


Compiler options

Compiler options

  • Common options

    • -o specifies compiler output file

    • -l specifies libraries that should be linked

    • -L specifies library paths (important)

    • -i specifies files to include

    • -I specifies the path for include files

    • -i/-I/-l/-L can occur multiple times


Compiler options1

Compiler Options

  • Many compile/link options

  • Many optimization options (more on this later)


Cs591x cluster computing

So…

  • Imagine that you wrote a program called simplehello.c …

#include <stdio.h>

main() {

printf("Hello, World:\n");

}


To compile with gcc

To compile with gcc

  • Like this…

    • gcc simplehello.c –osimplehello

    • If all goes well, you get a shell prompt (means no errors)

    • Review compiler errors carefully

    • Unresolved references usually means something is not defined/can’t find something


Cs591x cluster computing

Or …

  • With Intell c/c++

    • icc simplehello.c –osimplehello

  • With mpicc

    • mpicc simplehello.c –osimplehello

  • Note: different compilers may have different defaults/definitions


Cs591x cluster computing

… mpi…

  • We have to give the compiler more direction …

  • gcc hello.c –ohellogcc –lmpich –I/usr/local/packages/mpich/include –L/usr/local/packages/mpich/lib

  • icc hello.c –ohellogcc –lmpich –I/usr/local/packages/mpich/include –L/usr/local/packages/mpich/lib


Cs591x cluster computing

  • With mpicc

    • mpicc hello.c -ohellompi


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