GAMS World Forum

It is well documented in gams solver usage. https://www.gams.com/latest/docs/UG_SolverUsage.html#BASIC_USAGE_SOLVER_OPTION_FILE copy the following lines of code anywhere in your gams file. $onecho > cplex.opt iis 1 $offecho This will create the options file. You can then tell the solver to look for ...

Hi, Non-linearity should not affect eps-constraint method. You can use eps-constraint method for nonlinear models too. You have two objectives and you can always restrict one by epsilon and solve for the other objective. You do it for multiple epsilon to get a table (or pareto optimal curve). Hope t...

Ahmad, Are FCROPS and DOM set elements or they are set names? When you write in quotes, it implies they are set elements. If you have to set the lower bound for all xd, you would do xd.lo(fcrops, dom) = 0.0001; If you want to set lower bound for one of the elements say (fcrops1, dom1), you would use...

You can modify your code as follows (add singleton set, modify equations, and add a loop to solve). singleton set ii(i); objective.. z =e= sum(ii, sum(j, w(ii, j)) ); constraint1(ii, k)..sum(j,w(ii,j)*a(k,j))=l=1; loop(i, ii(i) = yes; solve ... ); The above code defines objective function as a sum o...

From CONOPT documentation: https://www.gams.com/latest/docs/S_CONOPT.html#CONOPT_GAMS_CONOPT_TERMINATION_MESSAGES The solution is a locally optimal interior solution. The largest component of the reduced gradient is less than the tolerance rtredg with default value 1.e-7. The value of the objective ...

What type of model do you have, what solver are you using? What's the size of the model? For something like CPLEX and LP/MIP, there are several useful guidelines/options mentioned in GAMS documentation. https://www.gams.com/latest/docs/S_CPLEX.html#CPLEX_PHYSICAL_MEMORY_LIMITATIONS https://www.gams....

When you have t-1 on the RHS, GAMS does not produce an equation for t = 1 because t = 0 is not defined. You can check this by using option limrow = 1000; and by reducing the size of your sets. This is a common type of equation in something like inventory balance. It is important to pay attention to ...

What is the tighter constraint tolerance that you are trying? Tolerance cannot be less than 1e-12. 1e-5 is already a good enough tolerance. But if a solution is feasible for 1e-5 and infeasible for lower tolerances (which means it is truly infeasible), then it tells me that your model is poorly scal...

It is possible. I assume you have an index for time periods. set i /i1*i4/ t /t1*t5/; parameter p(i,t); p(i,t) = 0.1; file name / ''/; put name; put p('i1', 't1'); putclose; display p; You can display the entire symbol using display or you can use put as I showed you above. If you have a variable, y...

Hi, Couple of logical flaws here. You want to linearize z1*z2 but if you still have a constraint w= z1*z2, your entire formulation will still be nonlinear. Second, even if you have w = z1*z2 constraint, you would want it to be a part of the model so it will be w =e= z1*z2. w = z1*z2 is simply an ass...