From mboxrd@z Thu Jan  1 00:00:00 1970
X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on polar.synack.me
X-Spam-Level: 
X-Spam-Status: No, score=-1.9 required=5.0 tests=BAYES_00 autolearn=ham
	autolearn_force=no version=3.4.4
X-Google-Thread: 103376,30dd116614f4610e,start
X-Google-NewGroupId: yes
X-Google-Attributes: gida07f3367d7,domainid0,public,usenet
X-Google-Language: ENGLISH,ASCII-7-bit
Path: 
 g2news2.google.com!news4.google.com!feeder.news-service.com!newsfeed.straub-nv.de!noris.net!newsfeed.arcor.de!newsspool1.arcor-online.net!news.arcor.de.POSTED!not-for-mail
Date: Fri, 21 Jan 2011 19:09:34 +0100
From: Georg Bauhaus <rm.dash-bauhaus@futureapps.de>
User-Agent: Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10.5; en-US;
 rv:1.9.2.13) Gecko/20101207 Thunderbird/3.1.7
MIME-Version: 1.0
Newsgroups: comp.lang.ada
Subject: Protected Objects And Many Processors
Content-Type: text/plain; charset=ISO-8859-1
Content-Transfer-Encoding: 7bit
Message-ID: <4d39cbde$0$6882$9b4e6d93@newsspool2.arcor-online.net>
Organization: Arcor
NNTP-Posting-Date: 21 Jan 2011 19:09:34 CET
NNTP-Posting-Host: c15240ff.newsspool2.arcor-online.net
X-Trace: 
 DXC=]e]ZIh3jG4\YI9]OHn9o5^A9EHlD;3YcR4Fo<]lROoRQ8kF<OcfhCO[4<1b:Cc>W@Tnc\616M64>ZLh>_cHTX3j]B8GXOE^je:U
X-Complaints-To: usenet-abuse@arcor.de
Xref: g2news2.google.com comp.lang.ada:17582
Date: 2011-01-21T19:09:34+01:00
List-Id: <comp.lang.ada>

Suppose I have a computer that has P processors of C cores each.
A program to be run on this computer has two shared data objects
and a number N of tasks, plus one.  Each task is a member of one
group of tasks, and one group communicates via exactly one of
the shared data objects.  The additional task can synchronize
data between the two shared objects.


    T(1,1)                          T(2,1)
  T(1,2)                               T(2,2)
   ...       PO1  --- TPlus ---  PO2   ...
  T(1,N/2-1)                           T(2,N/2-1)
    T(1,N/2)                        T(2, N/2)

The presence of shared data almost always triggers the idea
of employing protected objects, since these avoid the overhead
of task switching.  But availability of computing hardware seems
to renders this a weaker argument.

Are protected objects still the best choice on a computer
that has many processors and/or cores?

Will the program run just as well when written with only task
objects if and when the number of available processors is
sufficient, that is, C > N?