I have an optimization problem where i need to minimize the Total_Cost. I have the equations in AMPL format and i need to convert it to MATLAB. Can anybody help and correct my answer?

This is the first equation in AMPL:

minimize Total_Cost:
sum {i in CONTROLLER} kappa_c[i] * 
sum {j in LOCATION} tcn[i, j]

*tcn is a binary variable

This is after i tried convert it to MATLAB form:

% these values are given%
CONTROLLER = 9;
kappa_c = {1,2,3,4,5,6,7,8,9};
LOCATION = 9;
sum = 0;

for i = 1:CONTROLLER

      sum = sum + kappa_c{i};    

      sum1 = 0;

          for j = 1:LOCATION

              sum1 = sum1 + tcn{i;j};

          end

      ans1 = sum1 * sum ;

end
    display(ans1)

[Walter Roberson]

Your AMPL definition uses j as the loop control variable twice, and uses the undefined variable i . Your translation of it into MATLAB would be for the slightly different

minimize Total_Cost:
sum {i in CONTROLLER} kappa_c[i] * 
sum {j in LOCATION} tcn[i, j]

Answer 1

[Yogananda Jeppu]

sum1 = sum1 + tcn{i;j}; The ';' should be perhaps a ','. It is easier if you can represent as a matrix with [] square brackets. Use the sum function in matlab and .* to multiply elements instead of matrices.

[Amerul Rosle]

I changed my code slightly according to your answer and i get this error:

>> test1
Index exceeds matrix dimensions.

Error in test1 (line 15)
            sum1 = sum1 + tcn(i,j);

This is my code:

CONTROLLER = 9;
kappa_c = [1,2,3,4,5,6,7,8,9];
LOCATION = 9;
sum = 0;

for i = 1:CONTROLLER

      sum = sum + kappa_c(i);    

      sum1 = 0;

for j = 1:LOCATION

              sum1 = sum1 + tcn(i,j);

          end

      ans1 = sum1 * sum ;

end
    display(ans1)

Any suggestion?

[Walter Roberson]

Please do not use "sum" as a variable name; you confuse the readers, and there is better than a 95% chance that at some point you will attempt to use the function named sum() in a routine where you have used sum as a variable name.

[Walter Roberson]

What is size(tcn) ?

If you had not used sum as the name of a variable, you could replace the inner for loop with

sum1 = sum(tcn(i,:));

[Amerul Rosle]

Tcn is a binary variable

var Tcn {CONTROLLER, LOCATION} binary;

 1 if controller c in C installed on location p in P, otherwise 0

How would i declare Tcn in my code then?

[Walter Roberson]

It would just be an array. Just initialize it with appropriate content. For example,

tcn = [0 1 1 0; 0 0 0 1; 1 1 0 0; 1 0 0 0];

Is it the case that you are attempting to find the tcn that minimizes the total cost? If none of the entries are negative, the obvious answer would be the all-zero matrix, unless there are constraints that prohibit it.

[Amerul Rosle]

<<

>>

[Amerul Rosle]

It is true that none of the entries are negative, however there are some entries that are not zero, which makes all-zero matrix inappropriate to be used

[Walter Roberson]

tcn = randi([0 1], 9, 9);

If none of the entries are negative, then the tcn that minimizes will always be the all-zero tcn, which would give a cost of 0. With no negative entries it is not possible for the cost to be below 0, so all-zero minimizes.

The exception to this is if you have constraints such as "at least 2 locations must be turned on for each controller"

[Amerul Rosle]

Thank you Walter, much appreciated.