Newsgroups: comp.parallel
From: gelleric@kafka.informatik.uni-stuttgart.de (Wolfgang Gellerich)
Subject: Re: What is a barrier?
Organization: Informatik, Uni Stuttgart, Germany
Date: 13 Sep 1995 12:53:10 GMT
Message-ID: <436k7m$h2a@usenet.srv.cis.pitt.edu>

In article <4341na$9pd@usenet.srv.cis.pitt.edu>, ucaa2385@iris2.csv.ica.uni-stuttgart.de (Peter Hermann) writes:
|> Rudy Chukran (chukran@chukran.austin.ibm.com) wrote:
|> : Can someone give me a synopsis of what a barrier is and how
|> : it helps parallel computation. If that is too hard to do in
|> : a paragraph, can you suggest some literature to read?
|> [snip]
|> : Are barriers implemented as either language constructs or
|> : OS calls on UNIX or other platforms? AIX certainly doesn't have
|> : them. I am curious to what degree this barrier concept has been implemented
|> : elsewhere.
|> 
|> If you look deep enough into
|> the web-site http://lglwww.epfl.ch/Ada/
|> you will somewhere find the "Rationale"-document of the Ada95-standard.
|> In chapter 9 "Tasking" the protected records are described
|> and there is a neat example how barriers work (in 9.1 and 9.1.2)

As far as I know, the term barrier also has a more general meaning.
In the context of parallel processing, barriers are any point (e.g.,
in a program) where concurrent activities must synchronize. This
concerns Tasks as in Ada, but may also be important when compiling
parallel loops to a certain architecture.  You could look at some
books about parallelizing compilers (Zima/Chapman: Supercompilers for
Parallel- and Vector Computers or M. Wolfe: High Performance Compilers
for Parallel Computing). 

Regards,
  Wolfgang 


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|Wolfgang Gellerich                    gellerich@informatik.uni-stuttgart.de |
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