Newsgroups: comp.parallel.pvm
From: rdaoud@magnus.acs.ohio-state.edu (Raja B Daoud)
Subject: Re: pvm message passing timing
Organization: Ohio Supercomputer Center
Date: 13 Aug 1995 02:40:20 GMT
Message-ID: <40jomk$scv@charm.magnus.acs.ohio-state.edu>

Eve Li <eve_li@btgmax.zko.dec.com> wrote:
>compare two or more  such  systems besides taking samples alternatively
>and taking the avaerage (see below)?  

>Is there any flaw of the above system? Of course, one obvious flaw is
>that the spike noise  can hurt the measure . But as long as the noise
>is persistent during a measure of two systems, it will be balanced out.
>Very interesting problem, isn't it?

This is one case where I would take the min, not the average.  Since
at some time the application was able to achieve this min. timing in
a shared environment, it's very likely that if you were to take a
dedicated cluster and average several samples, this "good timing" will
be closer to the min. than to the average of the shared env. samples.
To be safe, one can take the average of the few smallest samples (say
the fastest 10-20% of the shared env. samples) or better yet, plot the
samples and only consider the cluster of min. samples (i.e. visually
filtering out the spikes in the graph).

--Raja

-=-
Raja Daoud				raja@tbag.osc.edu
Ohio Supercomputer Center		http://www.osc.edu/lam.html

