Intlinrprog (maximize) vs excel Solver (Maximize)

Dear All,

I tried to solve a problem that the objective is to find maximize value from X1, X2, and X3 and should be in integer. So, I use the intlinprog in Matlab to find the maximize value. Since I looking for maximize, I change "f" to "-f" and the result is negative number with the result 0 X1, 4 X2, and 2 X3. Attached below :

In confused why the result is negative. Then, I tried to solve the problem using Excel Solver (maximize) and I got a reasonable result below :

The confused things is, when I set the Excel Solver to minimize and also I remove "-" in Matlab (from "-f" to "f", the result will be same between the Excel Solver and Intlinprog Matlab.

Anyone here can help me, how to solve this problem ? How to use maximize function in intlinprog properly?

Thank you for your kindly help.

Answer 1

[Alan Weiss]

Your problem is that you set

intcon = 3;

This means that the only variable restricted to be an integer is x(3). Instead you should write the following:

f = [10 25 45];
intcon = 1:3; % All three variables are integer
A = [1 6 3;2 2 3];
b = [30 15];
Aeq = [0 5 2];
beq = 20;
lb = [0 0 0];
x = intlinprog(-f,intcon,A,b,Aeq,beq,lb,[])

LP:                Optimal objective value is -130.000000.                                          


Optimal solution found.

Intlinprog stopped at the root node because the objective value is within a gap tolerance of the optimal value, options.AbsoluteGapTolerance = 0 (the default value). The intcon variables are integer
within tolerance, options.IntegerTolerance = 1e-05 (the default value).

x = 3×1

3 4 0

Alan Weiss

MATLAB mathematical toolbox documentation

[Angga Fernando]

It works. Thank you so much for your kindly help.