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Hello there, I wonder if you could help me on the following contraint
This is how I understand this constraint can be translated on gurobi but I am getting a match error
Thank you in advance,
Hernani
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Hi Hernani,
What is the exact error you are getting? Could you post the code you have used so far to implement this constraint?
Best regards,
Jaromił0 -
Hi Jaromil,
My apologize I though I copy the code to the post. Here is how I coded the constraint,
model.addConstrs(
Regards,
quicksum(
x[u, v, i, 0] * math.log(1 - r_u[u]) + x[m, v, i, k] * math.log(1 - r_u[m])
for m in U
for k in range(K)
if u != m
)
<= math.log(1 - R_v[v])
for v in V
for i in range(C_u[u])
)
Hernani0 -
Hi Hernani,
I suppose \(r_u\) refers to a Gurobi variable. In this case, you cannot simply apply the logarithm to this variable and then use the result in a constraint. You first need to add auxiliary variables to capture these logs and then use those variables in the final constraint.
I hope that helps.
Cheers,
Matthias0 -
Hi Matthias,
Sorry I did not make it clear but the decision variables are x_uvik, r_u[u] and r_u[m] and R_v[v] are constants.
Regards,
Hernani
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Dear all,
I have this constraint (2) where x_uvik is binary decision variable and r_u, r_m and R_v are parameters to the problem.
I coded the problem as follow: But when I run my program with this constraint I get the model is unfeasible unable to retrieve attribute X. Could you please point me the right direction to solve this.
for v in V:constraint = LinExpr()constraint1 = LinExpr()for u in U:for i in range(C_u[u]):constraint.add(x[u,v,i,0]*math.log(1-r_u[u]))for m in U:for j in range(C_u[m]):if (u!=m):for k in range(K):constraint1.add(x[m,v,j,k]*math.log(1-r_u[m]))model.addConstr( constraint + constraint1 <=math.log(1-R_v[v]))Regards,Hernani0 -
Hi Hernani,
You could try to solve the IIS of this model to figure out what might be the cause of the infeasibility:
Model.computeIIS() (gurobi.com)Cheers,
Matthias0 -
Hi Matthias,
Thank you for quick response, regarding to the code of the constraint for your experience it seems correct or there is any suggestion you would like to share.
Regards,
Hernani
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The mathematical description seems to encode \( |V|*\sum_u C_u \) constraints, but it looks like you are only creating \( |V| \) constraints. Could that be the problem?
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