more stack exchange communities company blog Stack Exchange Inbox Reputation and Badges sign up log in tour help Tour Start here for a quick overview of the site Help Center Detailed link answered 06 May '15, 22:30 Ehsan â™¦ 4.7k●3●9●20 accept rate: 16% edited 06 May '15, 22:35 hi, I made \(j\) an alias of \(i\) and put apostrophes around all the First, one or more equation(s) statements declare names for the equations of the model. You may find it easier to you write down the equations themselves first, and then just above the equations you write the declarations.

Make all the necessary changes to the model so that the model works and the same values for X1 and Y result. Beginner modellers are recommended to use the more sophisticated syntax as much as possible (that is, if you understand the meaning), as this will make things much easier for you when A project is a system file you save but never have to touch. However, you first have to tell GAMS what the names of the variables are.

many thanks Mohammed Shuaibu PhD Candidate Department of Economics University of Ibadan -- You received this message because you are subscribed to the Google Groups "gamsworld" group. Explain why the model fails to get an optimal solution. Go to the right directory and make a new (or open an existing) project. The GAMS-IDE without any open files looks as follows: Once a .gms file is ready to run, the Run item on the main menu bar invokes GAMS.

Is there any way to know when NOT to use my Oyster card? The syntax is LOOP(SOL, *{add the commands you want for each element in set SOL, } *{these could be SOLVE statements, parameter calculations, et cetera } ); The loop A variety of standard functions may also be included: FunctionDescription abs()absolute value arctan()arctangent ceil()integer ceiling cos()cosine exp()exponential floor()integer floor log()natural logarithm log10()common logarithm max( ,..., )max of arg1, arg2, ... Clicking on any such red error message brings up the corresponding .gms file in the main GAMS window and positions the cursor at the point where the error was detected.

This $ is inserted immediately below the place in the line where the error arose (usually to the right). Solving more than one model The first three exercises at this intermediate level were rather superficial, though in practice they turn out to be very useful. variable wrong typeThe model has variable types not consistent with the problem type in the solve statement. Once a set name has been associated with some a variable, that same index name must normally be used whenever the variable is referenced.

In particular, clicking on Reading solution for model will open the .lst and position the window at the SOLVE SUMMARY. SUM( (i,j), X(i)*vars(i,4) ) =L= 50000; constr4.. This is a limited version of GAMS, which cannot solve large problems, but it may be handy when you are building proto-type models. ILP/MIP models need to set the optcr option, which specifies how much suboptimality is allowed when solution terminates.

Use of the semi-colon When you run the input file, GAMS will read the file you wrote line by line. Save your model, open a new project (go to file, project, new project) on the C-disk (for example: c:\mydocuments\models\gams.gpr) and open your gams file again. Lags and leads can be used for both parameters and variables, though there are some restrictions for use with variables. Note that these four categories are all represented in the solution listing as discussed above.

the index of neither that of a sum nor that of a system of constraints set under control alreadyA subscript is simultaneously used in two ways -- probably as the index The syntax is simply to assign the values yes or no to particular indices of the set. Sometimes you can get around this error by restructuring the equation (A*B=E=C instead of A=E=C/B). Remove the semi-colon after equation QX1.

but please firstly tell what did u added to make it better secondly the two errors remaining are saying: unrecognizable item- skip to find anew statement second is identifier expected and The general structure of GAMS programs The first step in modelling in GAMS is to write an input file. you’ll learn how to do two different simulations with the same model. Repair the error and save the correct file.

Give the file the name “intro”. Note: the following changes are within the existing code; do not add these lines to the end of the file. § Change the model to include a new set J This parameter block now looks something like this: PARAMETER coef(T) Emission coefficient CO2 OTHER(T) Emissions of other greenhouse gasses; coef(T) = 0.03; OTHER(T) = 5; Add an index T Error 036 '=' or '..' or ':=' or '$=' operator expected -or- Error 037 '=l=' or '=e=' or '=g=' operator expected Remember when giving a value to a parameter you use

Lower bounds are very useful if you have an equation that is invalid if a variable becomes zero (for instance Z =E= X/Y; if Y is zero, then Z is undetermined). This gives a clue on the robustness of the model with respect to the specification of the model. Is this possible? Though it is not strictly necessary, normally a GAMS input file has a file-extension .gms.

Provide starting values for CO2 and EMIS of 1 and 6 for each period. could be because of something like $X(â€²3â€²)$ (10 May '15, 03:45) alexmath @alexmath: The problem is with the last column (i.e., column "5"), not the first row. For example an equation may exist for all i and all j> i. Do you think the relationship between damages and build-up emissions is realistic?

Type the simple model as presented at the end of Section 1.4. (see page 10) Write all the basic blocks of code (parameters, variables, equations, model, solve). Several examples are provided below. While Loops Classic while loops can also be implemented to repeat activies until a condition is fulfilled. The error messages are generally self-explanatory and will not be listed here.

Specific elements like v1 have to enclosed in '', like 'v1', but generic elements used for sums etc. The second part of each SOLVE SUMMARY details results for all decision variables. Notice that the model has now become non-linear.