[Help-glpk] Upper bound problem

[Graciela Coitinho]

Hello!

First of all, excuse my bad english. Im new at mathprog and trying to model some problem i get as output some strange thing:

   No.   Row name        Activity     Lower bound   Upper bound
------ ------------    ------------- ------------- -------------
    .....
    .....

     7 constraint[1]
                                   0                          -0 
     8 constraint[2]
                                   0                          -0 
     9 constraint[3]
                                  -3                          -0 
    10 constraint[4]
                                  -2                          -0 

I dont get why those values happen at this constraint, because neither of the variables or values are negative in the first place. The constraint is defined as follow:

s.t. constraint{j in 1..n}: sum{i in 1..m} d[i,j] <= m * y[j];

Where m is a param defined in the data, positive integer, y is a binary variable and d[i,j] are real variables between 0 and 1 (0<=d<=1)

Any help would be greatly appreciated!! thanks in advance