Originally posted by: bluemoon32

Hello everyone. I wrote a code for a balanced transportation problem. I get the data from an excel file. My dat. and mod. files are below. I got an error when I run it, it says the size of the range is not the size of the array. I guess the problem is in the demand range. How can I solve this problem? I also attached the xlsx. file. Thank you.

dat. file

m=3;
 n=4;
 
 SheetConnection data ("Book1.xlsx");
 
 supply from SheetRead (data,"supply");
 demand from SheetRead (data,"demand");
 cost from SheetRead (data,"cost");

mod. file

// parameters
 
 int m=...; // Number of plants
 int n=...; // Number of cities
 
 range plants=1..m;
 range cities=1..n;
 
 float cost [cities]=...;
 float supply [plants]=...;
 float demand [plants]=...;
 
 // Decision Variables
 
 dvar float+ x[plants][cities];
 
  minimize sum (i in plants, j in cities) cost[i] * x[i][j];
 
  subject to {
  forall(i in plants)
   demandc:
    sum(j in cities) x[i][j] <= supply[i];
    
  forall(j in cities)
     supplyc:
     sum(i in plants) x[i][j] >= demand[j];    
  }
 

Hi,

without changing the xls I would rewrite your .mod into

// parameters
 
 int m=...; // Number of plants
 int n=...; // Number of cities
 
 range plants=1..m;
 range cities=1..n;
 
 float cost [cities][plants]=...;
 float supply [plants]=...;
 float demand [cities]=...;
 
 // Decision Variables
 
 dvar float+ x[plants][cities];
 
  minimize sum (i in plants, j in cities) cost[j][i] * x[i][j];
 
  subject to {
  forall(i in plants)
   demandc:
    sum(j in cities) x[i][j] <= supply[i];
    
  forall(j in cities)
     supplyc:
     sum(i in plants) x[i][j] >= demand[j];    
  }

regards

Originally posted by: bluemoon32

Thank you. It works. I see that you only add [j] dimension to the objective function. I am little confused why it does not work other way. For example,

minimize sum (i in plants, j in cities) cost[i][j] * x[i][j]; gives me error, but cost[j][i]  works.

Because one dimension has 3 elements and the other one 4 so you cannot mix those.

regards