[Os-project-managers] NaN in xs:double (OSrL)

[Jun Ma]

Kipp,
It may help to think  an optimization like this:
maximize 1/0
subject to ......

the objective value should  return NaN.
At least in Java language, the official definition of NaN is 1/0.

Jun

--------------------------------------------------
From: "Kipp Martin" <kmartin at chicagobooth.edu>
Sent: Friday, February 04, 2011 8:15 PM
To: "Horand Gassmann" <Horand.Gassmann at dal.ca>
Cc: <OS-project-managers at list.coin-or.org>
Subject: Re: [Os-project-managers] NaN in xs:double (OSrL)

> Hi Gus:
>>
>> That is not how I remember the discussion from last time (or maybe the
>> time before that):
>>
>> <initialVariableValues numberOfVar="2">
>>     <var idx="0" value="NaN"/>
>>     <var idx="1"/>
>>
>> should set both x0 and x1 to NaN (this I am clear on) and should send
>> those values to the solver (this is how I understood the discussion, but
>> perhaps I misunderstood).
>
> No we don't send those values on to the solver, we send those to the OS
> solver interface. Consider Ipopt. We never give Ipopt a starting value
> of NaN for a variable. However, the OS Ipopt solver interface
> "intercepts" the NaN and replaces it with  1.7171. So we never send NaN
> to a solver.
>>
>> But even then, I maintain that diagnosing a solver error would be
>> greatly helped if there were some mechanism that allows the user to
>> pinpoint the variable or constraint or even objective that went awry.
>> And the only way I see for that to happen is a way that allows the
>> solver to return NaN to the user.
>
> Yes, I can see your point. But this may all be for naught. Can you come
> up with an actual example where the solver actually returns a NaN? I
> mean THE solver, not the interface.
>
> Cheers
>
>
>>
>> Another Can$ 0.02
>>
>> Cheers
>>
>> gus
>>
>>
>
>
> -- 
> Kipp Martin
> Professor of Operations Research
> and Computing Technology
> Booth School of Business
> University of Chicago
> 5807 South Woodlawn Avenue
> Chicago, IL 60637
> 773-702-7456
> kmartin at chicagobooth.edu
> http://www.chicagobooth.edu/faculty/bio.aspx?person_id=12825325568
> http://projects.coin-or.org/OS
>
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