Wenbo Ma

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Activity overview

Latest activity by Wenbo Ma
  • Wenbo Ma created a post,

    cbCut - Variable not in model

    Answered

    Hi, I was trying to add a user-cut through callback but encountered an error that I cannot resolve. There was always an GurobiError returned saying 'Variable not in model' due to the last 'model.cb...

  • Wenbo Ma created a post,

    Get variables by name

    Ongoing

    I have variable gamma indexed by a two-dimension list base_M (e.g. [1, 1], [1, 2], ..., [20, 2]) gamma = m.addVars(base_M, lb = gamma_lb, ub = gamma_ub, vtype = GRB.BINARY, name = 'gamma') I am won...

  • Wenbo Ma created a post,

    Crossover Takes Long

    Answered

    Hello, I have a large size MIP model and I could come up with a decent feasible solution (have set it as the MIP start value). In the current Gurobi solution process, the root crossover subprocess ...

  • Wenbo Ma created a post,

    Fix Certain Variables and Optimize the Rest

    Ongoing

    Hi, I have a MILP model solved to optimal. In the next step of my project, I plan to fix the values for certain variables in my model, re-assign parameter values based on new data and re-optimize t...

  • Wenbo Ma created a post,

    Solver is Frozen

    Answered

    I was solving a large MILP problem. On a Linux server with Gurobi 9.1.2, the solver is always stuck solving the root node LP. However, I didn't have this problem when I tested the same problem on m...

  • Wenbo Ma created a post,

    How to Check Which Version of Gurobi is Being Used

    Answered

    I am on a Linux server with user access (no admin access). I installed python by installing Anaconda and then installed Gurobi use Conda install Gurobi. However, I know there are other versions of ...

  • Wenbo Ma created a post,

    How Can I Locate the Constraints that Causing Infeasibility

    Answered

    I have a large-scale model with 1.7 million rows. My initial test gives me the result that the model is infeasible. I am wondering if there is any function I can use to locate which constraints cau...

  • Wenbo Ma commented,

    Just add a note to Eli's answer: If you don't want to create a new object LHS, below can give you the values too. for proc in procs: quicksum(RestrProc2[proc][vr]*Vrbl[vr] for vr in vrs).getValue()