[Os-project-managers] OSrL problem

[Horand Gassmann]

Kipp Martin <kmartin at chicagobooth.edu> wrote:

> Hi Gus:
>>
>> But when we get stuff back from the solver and have to pass it back into
>> an AML, we are stuck. *We* have to know what the AML calls the type; we
>> cannot ask Ipopt to call it "r", because we have no way (and no reason)
>> to tell Ipopt that the input file was generated by AMPL. Do you have any
>> clever ideas about that?
>
> Why not do what you suggest in the previous email and have a type in  
> the <other> element.  Then each solver interface that writes to the  
> <other> can write the type which comes from an enumeration. Then the  
> AML interface reads the type and uses as appropriate for the AML.

I'll have to kick this around a bit more. It ought to work, but maybe  
there is a trick somewhere. What about the following scenario: AMPL  
can have a user-defined subscript of type "binary". AMPL can only  
transfer this as an integer, so when sending such info to the solver,  
it translates false to 0 and true to 1 and sends that. And it can only  
accept integer or real values, making internal translations back into  
the original form when necessary.

  But when the stuff comes back from the solver, can we rely on the  
solver storing it internally as integer also? I am not sure. If the  
solver sends it as boolean, I guess we can make the translation  
ourselves, but what if the solver sends it back as a string? Is that  
possible? Plausible? Something we need to worry about?

There are also string-valued suffixes in AMPL, but they can have only  
finitely many values --- i.e., an enumeration --- and AMPL translates  
the enumeration into a table and sends an integer --- and it expects  
an integer corresponding to that table in return. I hope we do not end  
up having to store the enumerations at our end.

Cheers

gus

-------------------------------------------------------

Horand I. Gassmann, Professor

School of Business Administration, Dalhousie University
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