Frustration, Depression, Nastyness

[Jens Grabarske]

Ok... false alarm... I'm stupid...

The error was not in this code but in the code of the clients.

Kind regards,

Jens

Am Montag, 10. Januar 2005 21:17 schrieb Jens Grabarske:
> Hello, all!
>
> It's 9pm and I'm still at work because my Oz does strange things.
> Here's the thing:
>
> In my architecture I have several clients waiting for a master thread to
> feed them stuff to do (distributed-programming-like).
>
> The idea is that the master looks up some stuff in a database (using the
> postgres library that can be found in the contrib-directory) and generates
> closures for the clients to be executed by mapping a generator function
> over the data sets.
>
> Now, the function that is supposed to generate the closures looks like
> this:
>
>    fun {GenerateScanClosure ScanDS}
>       fun {$ Command}
> 	 [CodeMOD] = {Module.link [ScanDS.code]}
>       in
> 	 case Command
> 	 of start then
> 	    {CodeMOD.start ScanDS.argument ScanDS.ip}
> 	 [] tidy then {CodeMOD.tidy}
> 	 end
>       end
>    end
>
> In my test situation, about 254 ScanDS structures are generated and passed
> to this function which generates 254 different functions. These functions
> are distributed to the clients. So far so good. The clients actually do
> execute 254 functions. And the results of these 254 functions get
> collected. But in the end it turns out that all these 254 function calls
> yield the same result - because they operate on the same set of data! (as
> you can see, there is an IP address in the field "ip". This ip address
> should be different for all 254 runs. But it's always the same).
>
> When I let GenerateScanClosure print the IP address it receives, I get 254
> different IP addresses. So the problem has to be in the closure binding. I
> guess that it has to be some optimisation going wild and letting the
> bindings follow the "current" data set.
>
> Does anyone see how I can make this work?
>
> Kind regards,
>
> Jens

-- 
Jens Grabarske (Research), DFN-CERT Services GmbH
https://www.dfn-cert.de, +49 40 808077-621 / +49 40 808077-555 (Hotline)

12. DFN-CERT Workshop und Tutorien, CCH Hamburg, 2-3. Maerz 2005
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