Path: utzoo!attcan!uunet!cs.utexas.edu!usc!zaphod.mps.ohio-state.edu!swrinde!emory!hubcap!lush
From: lush@EE.MsState.Edu (Edward Luke)
Newsgroups: comp.parallel
Subject: Re: Acceptable efficiency factors
Message-ID: <9513@hubcap.clemson.edu>
Date: 29 Jun 90 15:59:38 GMT
Sender: fpst@hubcap.clemson.edu
Lines: 24
Approved: parallel@hubcap.clemson.edu

In article <9508@hubcap.clemson.edu> xxremak@csduts1.lerc.nasa.gov (David A. Remaklus) writes:

>   In a recent conversation with some colleagues of mine at the Ames NAS
>   facility concerning parallel processing, they mentioned their experiences
>   porting a code to the Intel i860 hybercube located there (128 nodes,
>   7.5 gigaFLOPS peek).

ANY peak performance number is bogus.  A peak number can be considered
as a number "guaranteed not to exceed", and no more.  Intel claims
that the i860 can put out something like 80 Mflops peak, but you would
be lucky to get 10 Mflops out of one on real applications.

>   It is our contention that it is necessary to achieve an efficiency factor
>   of at least 50% before the particular implementation of the code can be
>   considered appropriate for execution on that parallel processor system.
>   What are your opinions on this matter?  Are there any published papers
>   that deal with this subject?

I would say that the most important factors are:

1)  Cost per *real* Mflop
2)  Mflop value required by the application.  
    (Application A requires 300 Mflops to run in one hour)
3)  Ease of programming, or program development time.