From mboxrd@z Thu Jan  1 00:00:00 1970
Date: Sat, 17 Oct 2009 04:03:16 +1100
From: Sam Watkins <sam@nipl.net>
To: Fans of the OS Plan 9 from Bell Labs <9fans@9fans.net>
Message-ID: <20091016170316.GA3135@nipl.net>
References: <20091015105328.GA18947@nipl.net>
	<0d5ebfeb839e02bce3fb8511d6a32ce5@hamnavoe.com>
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Subject: Re: [9fans] Barrelfish
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On Thu, Oct 15, 2009 at 12:50:48PM +0100, Richard Miller wrote:
> > It's easy to write good code that will take advantage of arbitrarily many
> > processors to run faster / smoother, if you have a proper language for the
> > task.
>
> ... and if you can find a way around Amdahl's law (qv).

"The speedup of a program using multiple processors in parallel computing is
limited by the time needed for the sequential fraction of the program."

So it would only be a problem supposing that a significant part of the program
is unparallelizable.  I can think of many many tasks where "Amdahl's law" is
not going to be a problem at all, for a properly designed system.

For example if I had a thousand processors I might raytrace complex scenes for
an animated game at 100 fps, or do complex dsp over a 2 hour audio track in one
millisecond.

I suppose most difficult/interesting tasks can be parallelized effectively.
Seems that Amdahl's law is a minor issue.  Of course if you are trying to run
old-fashioned sequential programs on a parallel machine you will not benefit.
You would need to rewrite them.

Sam