Hi I have a MIP problem and I coded it in GAMS. But When I used conditional terms (IF rule), The games showed error: "Endogenous relational operations require model type "dnlp"" This error occurs when I add constraint: con8(i,j,n,k)..x(i,j,k)$((U-T(k)-(D(j,n)/V))>0)=l=x(j,n,k) ; In this constraint T(k) is the variable which has been calculated from other constraints. I find out that if I remove T(k), the GAMS works truly. Could anybody help me?
asked
majid |

Using a variable after the dollar is in most cases a recipe for disaster for NLP solvers (you introduce a discontinuity here). You should reformulate things or if you know what you are doing, explicitly solve as a DNLP model (probably after rewriting the constraint with an ifthen function) .
answered
erwin |