Behavior changing when adding intermediate variables
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Hi, I am working with Gurobi 9.12 for a jupyter notebook, and in it, I have a constraint
m.addConstr(1800-t_c[l]+t_c[i]<=M*(1-O[l,j]*O[i,j]))
Where t_c[l] and t_c[i] are continuous variables and O[l,j] and O[i,j] are binary variables, and my program runs fine and gives good and reasonable solutions, but when I introduce an intermediate variable to replace O[l,j]*O[i,j] since I am working to remove quadratic constraints, like the following:
tempvar1 = m.addVar(vtype = GRB.BINARY)
m.addConstr(tempvar1 == O[l,j]*O[i,j])#Just for testing
m.addConstr(1800-t_c[l]+t_c[i]<=M*(1-tempvar1))
The program is suddenly infeasible. There are no other constraints on tempvar1 or t_c, and the only other constraint on O is
print('Only look at 1 item at a time')
for i in range(len(O)):
m.addConstr(np.sum(O[i])==1)
Does anyone have any advice about why adding this intermediate variable might change the behavior of the optimizer and what I can do to prevent it from happening?
Solved it! It looks like the fact that it was working was actually a bug, when i=l, the constraint collapses to something infeasible, which for some reason wasn't catching in the compiler in the original statement
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Can you please post a complete minimal working example that includes the definitions of \( \texttt{O} \), \( \texttt{t_c} \), and \( \texttt{M} \)?
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