Newsgroups: comp.parallel
From: jim@meiko.co.uk (James Cownie)
Subject: Re: Help - explain superlinear speedup?
Organization: Meiko Ltd.
Date: Thu, 26 Jan 1995 14:28:12 GMT
Message-ID: <3g7slu$m8q@hub.meiko.co.uk>

Joel Williamson  <joelw@convex.convex.com> wrote:
>Superlinear speedups always result from additional resources (almost
>always memory) relieving bottlenecks in the computation.

David Bakken <dbakken@bbn.com> added
>I would say "usually" here, not "always".  Superlinearity can sometimes be
>the result of architectural specialization.

Another possiblity for superlinear speedup can occur in searching problems.
Consider searching an array of size N for a particular value, where by chance that
value occurs half way down the array. If we run on one processor, we will find
the value in time N/2. Give it to two processors with a block split and the 
second processor will find it in time 1. (Since it'll be the first element
it looks at). With a big enough array you can get an arbitrarily large
superlinear speedup !

--Jim 

James Cownie 
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