Krypt

I am solving an MIP. I noticed that if I change the order in which constraints are added slightly, it drastically affects the solution runtime. Currently, I have an MIPGap = 1%. One order gets to t...

Hello, I am trying to implement column generation. Right now, I am redefining the model and solving it from scratch every time I generate a new column, this is very inefficient. I am wondering if t...

I am trying to solve a vehicle routing problem using a branch and price algorithm. At the restricted master problem  (RMP), we consider two branches: we enforce an arc (a,b)=0 and  (a,b)=1 (I am fo...

Hi, My optimization model contains constraints with variable multiplications and divisions. For example, I want to add constraints like below: mdl.addConstr(x/y >= (1/z) + epsilon)mdl.addConstr(x/(...

How do I define user cuts at a branch and bound node similar to lazy constraints in a callback?

When I see the log of my milp model I see the following line appears: Root relaxation: objective 2.551315e+03, 541 iterations, 0.01 seconds (0.01 work units) What does this mean? How is it differen...

Hi, I am trying to model a conditional constraint in Python Gurobi. Here x_e is a binary variable, z and b are continuous variables and r is a parameter. if b[e,i] >=0.8 then z[e,j] >= x_e[e,(i,j)...

I am solving a routing problem where I want to delete an arc x[i,j] (binary variable) if a certain condition is met. How do I efficiently do this? Do I use model.remove? for i in N: for j in N: ...

Hello, I am trying to solve a MIP in Gurobi, but it is taking a long time (see screenshot). I know the exact optimal solution is 31827.39074. As you see, the solution is very close to the exact op...

Hello, I am encountering keyError at the constraint highlighted in bold. The reproducible code is below. I want to have a set of constraints where my binary variables X are summed up to L[i]. I wan...