Eli Towle

Hi Johannes, To be concise, we can use a single binary variable \( z \) to represent the sign of the variable \( m \): $$\begin{align*}z = 1 &\iff m \geq 0.\end{align*}$$ We can equivalently write ...

Hi Liu, The definition of the \( \texttt{space} \) variables doesn't look right: space[i,j,t] = m.addVar(vtype=GRB.BINARY, name='space%s_%s_%s'%(i,j,t)) It looks like these should be continuous (an...

Hi Lars, The setup is the same. You just need to specify your Cloud credentials when solving a model. In the Cloud Manager interface, navigate to Settings->API Keys. If you do not have an API key ...

Hi Liu, The two formulations both look okay to me. Could you post a small code snippet that has the same result (one model feasible, the other infeasible), but includes the definitions of all varia...

Hi Wu, Yes, you can do this with a callback. A similar question was answered here. I'll re-post the code below. It generates a list of times, incumbent objective values, and best bounds using a cal...

Hi Sneha, How big is your model? Also, do you know exactly where in the code the network connection error appears? Individually querying string-valued attributes like VarName can be very inefficien...

Hi Erik, This constraint doesn't quite make sense: $$\begin{align*} \sum_{t \in T} \sum_{i \in V^{\omega}} \sum_{\omega \in \Omega} x_{ijt} \cdot (t+c_{j0}) &\leq t^* \qquad \forall \; j \in V^{\om...

Hi Wu, You're right that you cannot directly obtain the MIPGap from a callback. However, you can easily calculate the gap yourself using the incumbent objective value (\(\textrm{ObjVal}\)) and the ...

Hi Hanxiong, The abs_() function is used to set one variable equal to the absolute value of another. You should first define an auxiliary variable and set it equal to \( x - y \). Then, introduce a...

Hi Hooman, I'm not entirely sure what each of these constraints is trying to do, but you're right that the current constraints don't make sense together. Is there a mathematical formulation you are...