hey, i was running a model on gams with cplex as solver and found that i didnt get an optimal solution, because i did the same model on lingo and got a better one,(compared the solution and find the lingo one feasible, so its not a problem in the model itself). i think it might be due to some cplex tolerances or heuristic methods or smth i dont know. Is there a way to fix this, making cplex solve with 0 tolerance or something?. (dont know how to enter to cplex parameters and options neither). btw i added a constraint forcing gams to make a better solution(the lingo solution) and it made it with no problem,so its not about the model its about the solver. thanks in advance asked 03 Jun '16, 01:43 jmslaterc 
The default relative gap parameter in GAMS is 10%. So, the solver would stop after finding a feasible solution within the 10% distance of the bound (hence, it's not necessarily optimal anymore). To change this behavior, use the following command with your desired gap.
The above command set the relative gap to 0.001 percent. PS. To change the absolute gap parameter, use the keyword optca. answered 03 Jun '16, 03:24 Ehsan ♦ Thanks for the quick answer, it was indeed the relative gap parameter that made me get diff solution.
(03 Jun '16, 18:10)
jmslaterc
