Multiple allocation p hub median with lots of error

GAMS
1 
  sets
i non hub node i /1*81/

*/p city /1*81/
Alias(i,j,k,m)  ;



Parameters
a discount /0.7/
c(i,j,k,m)  /c(i,k)+c(m,j)+(a*c(k,m))/

table t(i,k) average amount of commodities from i to j
$include C:\Users\Asus\Desktop\appendixs\Appendix3.inc
;

table d(i,j) distance between i and j
$include C:\Users\Asus\Desktop\appendixs\Appendix1.inc
;
table c(i,k) cost between i and j
/5*d(i,j) /


table h(i,j) connection between i and j
$include C:\Users\Asus\Desktop\appendixs\Appendix2.inc
;



Variable
z objective
p hub
y(i,k,m) i düğümünden çıkarak k ve m düğümünden geçen akış miktarı

binary variable
x(i,k)  i düğümü k hub ına atanırsa
x(k,k)  k düğümü  hub olursa

positive variable
x(i,j,k,m) the total flow for each origin–destination pair

;

Equation
obj objective function
cons1
cons2
cons3
cons4

;

obj.. z=e=sum(i,sum(j,sum(k,sum(m,(h(i,j)*x(i,j,k,m)*c(i,j,k,m))))));
cons1.. sum(k,(x(k,k)))=e=p ;

cons2(i,j).. sum(k,sum(m,(x(i,j,k,m))))=e=1   ;

cons3(i,j,k,m).. x(i,j,k,m)=l=x(k,k);

cons4(i,j,k,m)..  x(i,j,k,m)=l=x(m,m);



model project /all/;

solve project using mip minimizing z;
display z.l,x.l, y.l;

This is my code releated to Campbell multiple allocation p-hub median problem. can you help me to fixed errors?

2
  1. It is not clear what you are trying to achieve with this line.
c(i,j,k,m)  /c(i,k)+c(m,j)+(a*c(k,m))/

First of all, it is not executed while declaring parameters. But even if it is, GAMS does not know what is c(i, k) etc.

  1. It is not a good practice to have the same symbol (x) as binary as well as positive variable.
  2. you can define
    table c(i, j);
    followed by the operation instead of doing it between / /
    c(i, j) = 5*d(i, j);
  3. If you define c over the domain (i, j, k, m), it makes no sense to use c(i, k) or c(m, j). From the point you declare, c should always have 4 indices.

There are many fundamental issues with the code. I suggest looking at GAMS tutorials, specially parameters.
To get your code to work, you can follow a step by step procedure. First declare parameters, populate those with values and use display. You can ignore rest of the code with $exit.

Please note that the part where you assign values to parameters is executed sequentially. For example, you cannot use c before you assign values to it (which you do using d and you read d after you use c).

  • Atharv
3

Thank you for your support