Re: [foxboro] More FoxAPI/OM optimization questions

On Thu, Dec 19, 2002 at 11:46:53AM -0500, Grumelart, Alain wrote:
> 
> I can offer the following clarifications if it may help.

This is turning inot an interesting discussion.

I've got a couple of followup questiosn, please.

> 
> In order to achieve peer-to-peer communication between two I/A station,
> which is what FoxAPI is doing with its datasets,
> Yous need to have one or more omlist opened on both the source and the
> target
> (or sink) stations.
> If the AW is getting data (let's say 10 variables)from one CP 
> then the situation is straight-forward.
> You need to open one omlist of 10 variables on both the AW and the CP.
> 
> If the AW is getting data from multiple CPs (let's say 10 variables from 2
> CPs)
> then things get more complicated.
> 
> You can open one omlist on the AW.
> If the variables in the list are sorted so that all the variables
> from the first CP come first and are followed by all the variables 
> from the second CP, then it will be necessary to open only one omlist
> on each CP to source the peer-to-peer connection.
> If the variables in the AW's omlist are not sorted then it will be necessary
> to open one omlist on each cp to source each group of consecutive variables
> in the AWs list that come from that CP.
> 
> The worst case would be if the AW's omlist variables were ordered so that
> each odd position contained a variable from one CP and each even position
> contained a variable from the other CP.
> This would required 10 omlists on each CP to source the peer-to-peer
> connection.
> 
> You can minmize the number of omlists required on the CP by making sure
> "somehow"
> that the variables in the AW omlist are ordered properly.

How would one control the order that FoxAPI orders lists in?

> 
> An other way to minimize the number of omlists required on the CPs is to 
> use more than one list on the AW.
> For the above example, if you open 2 omlists on the AW, ie one for each CP,
> then you are sure that you will need only one omlist on each CP 
> to source the connection. 
> This holds true as long as the number of variables is sufficiently small 
> to fit in one omlist. If the number of variables does not fit in a
> single om list, then things get even more complicated but the principle
> remains the same.

Ok, what are the size limits of om lists?

Thanks for the education here.

-- 
"They that would give up essential liberty for temporary safety deserve
neither liberty nor safety."
                                                -- Benjamin Franklin
 
 
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