Adding conditional IntVar to Objective Function

[ngaihiang]

How can I add IntVar to my objective function only when some conditions are met?

obj_int_vars,  obj_int_coeffs = [], []
obj_bool_vars,  obj_bool_coeffs = [], []

elephant_is_healthy = dict()
elephant_weight = dict()

num_elephants = 20
num_months = 10

for e in range(num_elephants):
     for d in range(num_months):
        # Assuming some months elephants are healthy, some months they are not
        # Track if they are healthy with boolean
        elephant_is_healthy[e,d] = model.NewBoolVar('elephant%i_%i' % (e, d))

        # We also want to track elephants monthly weight. 
        elephant_weight[e,d] = model.NewIntVar('elephant%i_%i' % (e, d))

# Assuming there are some rules to update elephant_is_healthy and elephant_weight to 
# determine if they are healthy and their monthly_height

# Now for some reason, I need to add the weight of ONLY healthy elephants into the objective function,
# how can I do this? Since I need to first find healthy elephants and then find their corresponding weight

for e in range(num_elephants):
    for d in range(num_months):
        obj_bool_vars.append(elephant_is_healthy[e,d])
        obj_bool_coeffs.append(elephant_weight[e,d]) --> seems like this can only take a number, not an IntVar. 
        # How can I access this value into the objective function?

model.Minimize(
    sum(obj_bool_vars[i] * obj_bool_coeffs[i]
        for i in range(len(obj_bool_vars))) +
    sum(obj_int_vars[i] * obj_int_coeffs[i]
        for i in range(len(obj_int_vars)))
)

It will throw an error that looks like
TypeError('Not an number: ...

Thanks in advance!

[lperron]

Please read https://github.com/google/or-tools/blob/stable/ortools/sat/docs/channeling.md