mixed-integer-programminggams-mathinteger-programming

GAMS Error in MIP Transportation Problem - Uncontrolled set entered as constant

I am trying to formulate an MIP model in which a transportation can be performed by available trains or new ship investments. My current code includes three tables: Monthly costs for trains, monthly costs for ships and initial investment costs for ships.

It raises the following error n149 at the "cost.. z =e=" line: Uncontrolled set entered as constant. Also errors with codes 257 and 141 are raised at the 56th and 57th rows, respectively.

Sets
i supply nodes /Plant1, Plant2, Plant3, Plant4/
j demand nodes /City1, City2, City3, City4, City5, Dummy/;

Parameters
a(i) supply capacities
         /Plant1 290
          Plant2 220
          Plant3 180
          Plant4 280/
b(j) demands
         /City1 180
          City2 200
          City3 160
          City4 140
          City5 250
          Dummy 40/;
Table c1(i,j) transport costs for trains
                 City1   City2   City3   City4   City5   Dummy
         Plant1  8.5     7       8       6.5     9       0
         Plant2  7.5     8       7       10      8.5     0
         Plant3  11      6       6.5     8       7       0
         Plant4  9       7       12      6       7.5     0       ;

Table c2(i,j) transport costs for ships
                 City1   City2   City3   City4   City5   Dummy
         Plant1  5.5     6       99999   3.5     4       0
         Plant2  3       4.5     4       6.5     6       0
         Plant3  99999   99999   3       4       4.5     0
         Plant4  5       4.5     7       3       99999   0       ;

Table in(i,j) investment costs for ships
                 City1   City2   City3   City4   City5   Dummy
         Plant1  40      90      99999   40      80      0
         Plant2  60      40      80      20      40      0
         Plant3  99999   99999   80      60      100     0
         Plant4  100     60      60      80      99999   0       ;

Positive Variables
         x(i,j)  flow between supply node i and demand node j;
Variables
         y(i,j)  whether a ship is bought for the trasfer from i to j
         z       total cost;
Binary Variables y;
Equations
         cost            objective function
         supply(i)       supply constraint
         demand(j)       demand constraint;

cost.. z =e=     sum((i,j), c1(i,j)*x(i,j)*12*10*(1-y(i,j)) + c2(i,j)*x(i,j)*12*10*y(i,j)) + in(i,j)*y(i,j);
supply(i)..      sum(j, x(i,j)) =l= a(i);
demand(j)..      sum(i, x(i,j)) =g= b(j);

Model homework1c /all/;
homework1c.OPTFILE=1;
Solve homework1c using MIP minimizing z;
Display x.l, x.M, y.l;

I would appreciate any suggestions to fix them, thanks in advance.

Solution

  • I see two issues: