Some Metacomputing Experiences for Scientific Applications

Abstract

We demonstrate good metacomputing efficiency and portability for three typical largescale parallel applications; one molecular dynamics code and two electromagnetics codes. The codes were developed for distributed memory parallel platforms using Fortran77 or Fortran90 with MPI. The performance measurements were made for a testbed of two IBM SPs connected through the vBNS. No change of the application codes were required for correct execution of the codes on the testbed using the Globus Toolkit for the required metacomputing services. However, we observe that for good performance, it may be necessary for MPI codes to make use of overlapped computation and communication. For such MPI codes, a communications library designed for hierarchical or clustered communication can yield very good metacomputing efficiencies when high-performance networks, such as the vBNS or the Abilene networks, are used for platform connectivity. We demonstrate this by inserting a thin layer between the MPI application and the MPI libraries, providing some clustering of communications between platforms.