Elsevier

Parallel Computing

Volume 9, Issue 3, February 1989, Pages 279-290
Parallel Computing

Synchronization and communication overheads on the LCAP multiple FPS-164 computer system

https://doi.org/10.1016/0167-8191(89)90113-0Get rights and content

Abstract

LCAP comprises an IBM-4381 host communicating with ten FPS-164 computers over I/O channels which have a measured effective transfer rate of about 2 Mbyte/s to each FPS-164. The FPS-164s may also communicate directly over a 22 Mbyte/s FPSBUS. This paper reports measurements of the startup overhead associated with these two methods of synchronization and communication as a function of the number of FPS-164 processors used. The significance of the overheads is interpreted in terms of the parameters f12 (floating-point operations per data transfer for half the peak performance), and s12 (grain size of parallelized problem for half the asymptotic performance). For channel communication f12 = 2 and s12 = 2 × 103 to 4 × 105. For FPSBUS communication f12 = 0.5 to 2.5 and s12 = 3 × 104 to 1× 106. Although the FPSBUS has about ten times the asymptotic transfer rate of a single channel, the startup time is longer than that of the channels and can hide this advantage unless the problem is large enough. Further, since the channels from the host to the FPS-164s work in parallel, their total transfer rate can exceed that of the FPSBUS for about ten FPS-164 processors or more. In this circumstance, we speculate that the channel connection would be faster than the FPSBUS for all problems. However, the LCAP system available did not have enough channels to test this directly.

References (6)

  • R.W Hockney

    r, n12, s12 measurements on the 2 CPU CRAY X-MP

    Parallel Comput

    (1985)
  • I.J Curington et al.

    Synchronization and pipeline overhead measurements on the FPS-5000 MIMD computer

  • F Darema-Rogers et al.

    VM/EPEX - A VM environment for parallel execution

    IBM Research Report RC11225 (#49161)

    (1985)
There are more references available in the full text version of this article.

Cited by (0)

View full text