[Swift-devel] Problem with iterate

[Ioan Raicu]

I think we are on the same page, that if you cannot resolve the 
dependencies, things just fall apart. The part I don't get, is why would 
you get a deadlock in this situation (which is where this whole 
discussion started from), as opposed to an error detecting that the DAG 
cannot be constructed? It seems that at the time of DAG construction (I 
assume this is the SwiftScript compilation stage), any failure to add 
nodes to the DAG due to unresolved dependencies should return an error 
and halt, rather than execute until the deadlock happens.

-- 
=================================================================
Ioan Raicu, Ph.D.
NSF/CRA Computing Innovation Fellow
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Center for Ultra-scale Computing and Information Security (CUCIS)
Department of Electrical Engineering and Computer Science
Northwestern University
2145 Sheridan Rd, Tech M384 
Evanston, IL 60208-3118
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Cel:   1-847-722-0876
Tel:   1-847-491-8163
Email: iraicu at eecs.northwestern.edu
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       https://wiki.cucis.eecs.northwestern.edu/
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Mihael Hategan wrote:
> On Fri, 2010-02-19 at 11:36 -0600, Ioan Raicu wrote:
>   
>> But doesn't the single assignment criteria prevent loops from
>> happening in the dependency graph?
>>     
>
> No. What you are probably thinking is that if each node in a graph would
> represent an assignment then the loop would only be executed once after
> which, due to single assignment, there would be an error.
>
> However the loop is not executed at all, because there is no way to
> satisfy the dependencies of both nodes (x depends on y and y depends on
> x).
>   

-- 
=================================================================
Ioan Raicu, Ph.D.
NSF/CRA Computing Innovation Fellow
=================================================================
Center for Ultra-scale Computing and Information Security (CUCIS)
Department of Electrical Engineering and Computer Science
Northwestern University
2145 Sheridan Rd, Tech M384 
Evanston, IL 60208-3118
=================================================================
Cel:   1-847-722-0876
Tel:   1-847-491-8163
Email: iraicu at eecs.northwestern.edu
Web:   http://www.eecs.northwestern.edu/~iraicu/
       https://wiki.cucis.eecs.northwestern.edu/
=================================================================
=================================================================


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