Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!usc!zaphod.mps.ohio-state.edu!sol.ctr.columbia.edu!emory!hubcap!fpst From: priol@irisa.fr (Thierry Priol) Newsgroups: comp.parallel Subject: Re: Question: Ratio of communication to calculation time Message-ID: <1991Apr13.075558.17444@irisa.fr> Date: 13 Apr 91 07:55:58 GMT References: <1991Apr11.190317.23509@hubcap.clemson.edu> Sender: news@irisa.fr Organization: IRISA, Rennes (FR) Lines: 36 Approved: parallel@hubcap.clemson.edu >From article <1991Apr11.190317.23509@hubcap.clemson.edu>, by sharieh@bind.cs.fsu.edu (a sharieh): > > Dear thinkers, > > I am running a Fortran code on the Intel iPSC/2. > If I define T_com to be the time to send a data unit of type > floating point from one processor to another, and > T_stu to be the time to start up a message( sending a message of > length 0), and > T_cal to be the time to do one floating point operations such as > a=b*c or a=b+c, > then what are the values of the following ratios: > T_com/T_cal, T_stu/T_cal? > Benchmarks on the last release (3.2) of the NX/2 give these results: T_msg = T_stu + k * T_com 1) message length <= 100 bytes T_stu ~ 360 micro-seconds / bytes T_com ~ 0.359 micro-seconds / bytes 2) message length > 100 bytes T_stu ~ 704 micro-seconds / bytes T_com ~ 0.359 micro-seconds / byte 3) Concerning T_cal, I have no result with FORTRAN) -- Thierry PRIOL Phone: 99 36 20 00 IRISA / INRIA U.R. Rennes Fax: 99 38 38 32 Campus Universitaire de Beaulieu Telex: UNIRISA 950 473F 35042 RENNES CEDEX - FRANCE E-mail: priol@irisa.fr -- =========================== MODERATOR ============================== Steve Stevenson {steve,fpst}@hubcap.clemson.edu Department of Computer Science, comp.parallel Clemson University, Clemson, SC 29634-1906 (803)656-5880.mabell