Simplexlp solver excel12/28/2023 ![]() The solver is usually letting you know if the solution is just "feasible" or if it is also optimal (like in this case):Īs you can see in the screenshot above, I have completely changed the way the tax payments are calculated. I was lucky and was able too find an optimal solution, which I didn't expect. In your case, I have used only the modelling tricks to get rid of the IF function (see piecewise linear function) and then used the GRG nonlinear solver. I use them once in a while, but most of the time it isn't even worth trying. These solvers aren't guaranteed to find an optimal solution and aren't even guaranteed to find a solution at all. So, what about the other solvers? Both the GRG nonlinear solver as well as the Evolutionary solver are based on heuristics. You could approximate the quadratic part using more piecewise linear functions, however, the problem will get way to big to model it in a reasonable way in Excel. However, the Excel Simplex solver still can't do it. The IF function is deadly in this context and can be eliminated (see piecewise linear functions) using additional variables.Īt this point, a solver like Gurobi could solve it since it supports quadratic terms under certain conditions. The rounding probably won't be necessary, so this is an easy one. You are rounding the tax payments (=INT(.)).Within the IF statements you have quadratic equations (Welcome to bureaucracy.Your problem is small, however, there are non-linear equations: The Simplex LP solver is the only solver that can guarantee an optimal solution, however, the problem size is somewhat limited and all of the constraints as well as the objective function have to be linear. There are different solvers in Excel that are suited for different types of problems: My question is, why does it do that and how can I get the solver to maximize the sum of the saved taxes? ![]() It simply divides the payments evenly over all 3 years, one third each. The solver also calculates, but the result is wrong. The constraint is that the sum of the payments (F6) must always be 17.000,00 €. The sum from the line Taxes saved should now be maximized with the solver. taxes saved: The difference between what I paid in taxes before (line 2) and what I would have to pay after deducting the income-related expenses (line 5).taxes after: Are the income taxes that are due on the salary from line 4 (again, according to the formula of the cell).salary after: is the amount of the row salary before minus the amount of payment.payments: The sum of payments to be paid per year (total 17000 after 3 years).taxes before: The income tax to be paid on the salary according to the formula given (in the cell).salary before: Is the sum of the gross salary in the respective year.That is, the payments must be distributed over the year so that the amount that can be reimbursed via the tax is as high as possible.įor this I have now assembled several lines. Income-related expenses in the amount of 17,000.00 € are to be distributed in such a way that as much of the tax as possible is reimbursed. However, the solver does not do what it is supposed to.īriefly to the background: In the problem the gross salary for the year 2021, 20 is given. I have a simple optimization problem and would like to solve it using Microsoft Solver.
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