GAMS World Forum

Hi
Your example is not clear to me. Either post your GAMS code or make your example more explicit, so people can try to find an answer for you.
Cheers
Renger

Hi
Take a look at "Calibration of Models with Multi-Year Periods" on http://www.mpsge.org/mainpage/mpsge.htm by Tom Rutherford.
Cheers
Renger

Hi Fady You write "... to create a simple LP program", but your constraints are not linear (they have a multiplication of variables). So, it is obviously not a simple LP. MIP is Mixed Integer Linear Program, so this will not work. This is a RMINLP (see https://www.gams.com/latest/docs/user...

Hi You can't use if-constructs in constraints, but you can use the $-operator (see the manual for more information) in your constraints if the condition relates to a parameter (not to a variable): This works parameter p(t); variable E(t), A(t), B(t); myeq.. E(t) =E= A(t)$(p(t)>0) + B(t)$(p(t) < 0); ...

Hi You have to loop over t as Gams doesn't allow this kind of direct assignment in an if-statement: loop(t, if (a(t) <=b(t), p(i,t)=a(t); else p(i,t)=b(t); ); ); You could do this, however using the dollar sign p(i,t)$(a(t) < b(t)) = a(t); p(i,t)$(a(t) > b(t)) = b(t); p(i,t)$... is pronounced as p(i...

Hi I probably would write a loop and then update PEXP as a parameter instead of a variable(you then do not define your variables over the set year anymore, so your model is just for one year and solve every time in the year loop). Some pseudo code: * initialize pexp for the first year pexp_prev(i) =...

Hi Yanzhiping
You should look at the error message you get when you submit your model to gams.
It clearly states that it is expecting a '=E=', '=L=', or '=G=' in your equation. You have a '=', which is not allowed in equations (see the manual).
Cheers
Renger

Hi
I probably would export the data in an excel sheet connected to Microsoft SQL using gdxxrw.
Cheers
Renger

set year 'All years' /2016*2050/;

set yearsub(year) Subset of years;

define subset


loop(year$yearsub(year),

....

);

Cheers
Renger

Hi
From your question it is not completely clear to me what you want. Is this what you are looking for (otherwise write down the mathematical expression for your question):

OBJ =E= sum((i,k), X(i,k)*C(i))


Renger