[Swift-user] Re: [Swift-devel] Problem with iterate

[Michael Wilde]

This old message slipped through by mistake when I cleaned up pending list admin requests.  Please ignore - its been discussed already.

- Mike

----- "Ioan Raicu" <iraicu at eecs.northwestern.edu> wrote:

> But lets bring this back to a more real example. A user wanting to
> express some computations that have some dependencies, would write out
> their computations in some order, expecting their order to be
> preserved because of the dependencies. If you only support single
> assignment on variables (e.g. the data), then an example like the one
> below could never deadlock because the single assignment would be
> violated on the 2nd statement. Perhaps things are more complicated if
> you support multiple assignments per variables, but that is not the
> case for Swift, right?
> 
> I am trying to understand if this deadlock is happening in Swift due
> to some particular implementation detail in Swift (or underlying
> pieces), or is it a fundamental flaw in the DAG based approach with
> single assignment variables? Or is it due to something completely
> different?
> 
> Thanks,
> Ioan
> --
> =================================================================
> 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/
> =================================================================
> =================================================================
> 
> Ben Clifford wrote:
> 
> 
> 
> Mathematically, the two different sequences evaluate to different
> values:
> 
> x = y + 1
> y = x + 1
> 
> assuming y = 0, x = 1 I mean in simultaneous equations (linear
> algebra) - in other words, "find
> (through whatever means you care to use) a value of x and y such that
> the
> above two equations are both satisfied" - there is no value of x and y
> that satisfies that. 
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-- 
Michael Wilde
Computation Institute, University of Chicago
Mathematics and Computer Science Division
Argonne National Laboratory