A question on bilevel programming

GAMS
1

Hello all,

I am new in this type of modelling and I am working on an example from EMP documentation.

I attach the following code:

positive variables x,y;
variables objout,objin;

equations defout,defin,e1,e2,e3,e4;

defout… objout =e= x - 4*y;

defin… objin =e= y;
e1… x + y =g= 3;
e2… 2x - y =g= 0;
e3… -2x - y =g= -12;
e4… -3x + 2y =g= -4;

model bard / all /;

$echo bilevel x min objin y defin e1 e2 e3 e4 > “%emp.info%”
solve bard using emp minimizing objout;


How can I see the emp.info file?

Also when running this example I get an infeasibility.

Thanks in advance,

Konstantinos Petridis

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2

Konstantinos,

The file %emp.info% is in the GAMS scratch directory. If you run with keep=1 (command-line switch) the scratch dir will be saved, typically with a name like 225a. The output will make this clear.

Since your empinfo file is a one-liner, I don’t know if seeing it will help you a great deal: you know what it contains already. Perhaps you’ll find the dictionary more useful. The dictionary is a mapping between variables in the original model and the variables in the reformulated scalar model produced by JAMS. If you have this in jams.opt:

dict
filename scalar.gms

and run like “gams mymodel.gms optfile=1” then you’ll get the scalar GAMS reformulation and the dictionary in the current dir and you won’t have to do a keep.

-Steve




On Wed, Dec 18, 2013 at 6:40 AM, Κωνσταντίνος Πετρίδης wrote:

Hello all,

I am new in this type of modelling and I am working on an example from EMP documentation.

I attach the following code:

positive variables x,y;
variables objout,objin;

equations defout,defin,e1,e2,e3,e4;

defout… objout =e= x - 4*y;

defin… objin =e= y;
e1… x + y =g= 3;
e2… 2x - y =g= 0;
e3… -2x - y =g= -12;
e4… -3x + 2y =g= -4;

model bard / all /;

$echo bilevel x min objin y defin e1 e2 e3 e4 > “%emp.info%”
solve bard using emp minimizing objout;


How can I see the emp.info file?

Also when running this example I get an infeasibility.

Thanks in advance,

Konstantinos Petridis

–
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\

Steven Dirkse, Ph.D.
GAMS Development Corp., Washington DC
Voice: (202)342-0180 Fax: (202)342-0181
sdirkse@gams.com
http://www.gams.com

3

Steve

thank you for your helpful reply.

Konstantinos Petridis

Τη Τετάρτη, 18 Δεκεμβρίου 2013 1:40:53 μ.μ. UTC+2, ο χρήστης Κωνσταντίνος Πετρίδης έγραψε:

Hello all,

I am new in this type of modelling and I am working on an example from EMP documentation.

I attach the following code:

positive variables x,y;
variables objout,objin;

equations defout,defin,e1,e2,e3,e4;

defout… objout =e= x - 4*y;

defin… objin =e= y;
e1… x + y =g= 3;
e2… 2x - y =g= 0;
e3… -2x - y =g= -12;
e4… -3x + 2y =g= -4;

model bard / all /;

$echo bilevel x min objin y defin e1 e2 e3 e4 > “%emp.info%”
solve bard using emp minimizing objout;


How can I see the emp.info file?

Also when running this example I get an infeasibility.

Thanks in advance,

Konstantinos Petridis

–
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