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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

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
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)
slide13
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
slide15
Or …
  • With Intell c/c++
    • icc simplehello.c –osimplehello
  • With mpicc
    • mpicc simplehello.c –osimplehello
  • Note: different compilers may have different defaults/definitions
slide16
… 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
slide17
With mpicc
    • mpicc hello.c -ohellompi
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