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From: xxrich@alliant1 (Rich Rinehart)
Newsgroups: comp.sys.alliant
Subject: Re: inter-loop locking
Message-ID: <1990Mar29.152045.28708@eagle.lerc.nasa.gov>
Date: 29 Mar 90 15:20:45 GMT
References: <1990Mar27.132340.4243@eagle.lerc.nasa.gov> <3768@alliant.Alliant.COM>
Reply-To: xxrich@alliant1.lerc.nasa.gov (Rich Rinehart)
Organization: NASA/Lewis Research Center
Lines: 54

>>I would like to force some MIMD like operation on the following 
>>loop but am having troubles figuring out the synchronization.
>>Can anyone be of help?  The problem is something like this....
>
>>  cvd$ concur
>>          do 100 I=1,100
>>             call sub1
>>             call sub2
>>  c do sub3 only after sub1 and 2 have completed
>>             call sub3
>>  100     continue
>
>
>As written, every iteration in the concurrent 'do 100' loop will be assigned
>its own processor, and each will execute its own copy of sub1 then sub2 then
>sub3, in order.  So as it stands, it will do exactly what you asked for, on a

This isn't what i wanted but i didn't realize this.  It would complete 100
iterations of sub1, then go on to sub2?

>However, I suspect perhaps you meant something different.  One possibility is
>to force *simultaneous execution* of sub1 and sub2, *then* do sub3:

Yes, this is what i wanted

>cvd$ cncall
>	do 100 I=1,2
>		if (I.eq.1) call sub1
>		if (I.eq.2) call sub2
>100	continue
>	call sub3
>
>The 'do 100' loop is a trick to create a concurrent loop with each iteration
>doing something different.  Again, no locks are required, but both sub1 and
>sub2 (and any child-subroutines) must be compiled 'recursive'.  (The test

Neat trick.
How can i guarantee that sub1 and sub2 will act in a mimd fassion?  What
if sub1 call other routines which the compiler might find what it thinks 
to be a 'better' loop to parallelize?   

Why must it be compiled recursively for this? (or is this the answer).

Thank you for your locking explaination as I plan to use it for another
analysis.

Thanks again for help!
-rich

--
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Rich Rinehart                  |     phone: 216-433-5211
NASA Lewis Research Center     |     email: xxrich@alliant1.lerc.nasa.gov
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