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Date: Thu, 03 Jan 2013 13:11:21 +0100
From: Georg Bauhaus <rm.dash-bauhaus@futureapps.de>
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Subject: Re: asynchronous task communication
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Date: 2013-01-03T13:11:08+01:00
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On 03.01.13 02:30, Charles Hixson wrote:
> I guess a part of the question is "What is the overhead on a protected variable?".  If it's small, then I'd prefer to have one attached to every cell, as it eliminates one centralized spot of contention, and means that slightly simpler messages can be passed.

Chances are that a protected object  employs a locking mechanism
of the OS (at least in a "PC run-time"). This is probably not the
fastest, leanest thing to have. However, I guess you could use
CAS based access to the letter boxes, in particular if the number
of messages is fixed.

Pat Rogers has illustrated an example, also referred to in Ada
Gems #93 and #98,
http://benchmarksgame.alioth.debian.org/u32q/program.php?test=chameneosredux&lang=gnat&id=2
http://www.adacore.com/adaanswers/gems/gem-93-high-performance-multi-core-programming-part-1/