Integer Solution to Minimize Daily Cost does not exist

Question

Hi! I’m working on my small project and I’m a beginner in programming and AIMMS.

I tried to run the model that I have developed but it resulted into “Warning: After zero iterations CPLEX 22.1 concluded that an integer solution to MinimizeDailyCost does not exist.” I attach my model and data.

I’m not sure where to start rectify this problem. Appreciate if anyone can help.

Marcel Hunting · Accepted Answer

Hi@Hazirah. I think that the integer variableNTUarea causes aconflict. There seems to be no feasible solution in whichNTUarea can have aninteger value.The model enforces NTUarea to take a fractional value but that is not allowed if this variable is declared as ‘integer’.If you change the range of NTUarea into ‘nonnegative’ then CPLEX is able to find a solution, with fractional values forNTUarea.

gabiservidone · Answer

Hi@Hazirah,I checked your model, and i have a few comments that may help you to find theinfeasibility source.Math Inspector (https://documentation.aimms.com/user-guide/creating-and-managing-a-model/the-math-program-inspector/a-worked-example.html#investigating-infeasibility) may be helpfull to find problematic constraints.Add a | 0 to inactivate a few non-core constraints to minimize what can be causing problems (ie. capacity constraints).Take a double look on variables and constraints domains. Inconsistencies can cause solves to fail.Make the use of inline variables (https://documentation.aimms.com/language-reference/optimization-modeling-components/variable-and-constraint-declaration/variable-declaration-and-attributes.html#variable-properties) to minimize this type of contraints:

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