Eli Towle

Gurobi Staff Gurobi Staff
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Activity overview

Latest activity by Eli Towle

  • Eli Towle commented,

    1. Community
    2. Programming
    3. Optimization using Gurobi

    It's valid syntax for the \( \texttt{if} \) statement to be at the end of the generator expression. It is not valid syntax to place the \( \texttt{if} \) statement before the \( \texttt{for} \) loo...

  • Eli Towle commented,

    1. Community
    2. Programming
    3. Optimization using Gurobi

    The problem occurs in this call to Model.addConstrs(): for g in n_generators:    for t in time_periods:        if t >= UT:           uptime[g,t] = m.addConstrs(sum(v[g,p] for p in range (t-UT+1, t+...

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  • Eli Towle commented,

    1. Community
    2. Systems
    3. grbgetkey: command not found

    It looks like the \( \texttt{PATH} \) variable still does not include \( \texttt{/opt/gurobi951/linux64/bin} \). What is the output of \( \texttt{echo \$PATH} \)? How did you set the environment va...

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    • Eli Towle
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  • Eli Towle commented,

    1. Community
    2. Programming
    3. gurobipy.Model.addGenConstrMin() Invalid data in vars array

    I generated an initial feasible solution from a reduced problem and I want to feed the MIP start of my larger instance with this solution. However, my constraint to penalize values below 60 is vio...

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  • Eli Towle commented,

    1. Community
    2. Algorithms
    3. GurobiError: Invalid argument to LinExpr multiplication

    It's okay to use a tuple as the dictionary key. The problem is that some of the dictionary values are tuples. These tuples are then multiplied by variables. Here is an example showing the source of...

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  • Eli Towle commented,

    1. Community
    2. Algorithms
    3. GurobiError: Invalid argument to LinExpr multiplication

    The problematic constraints are the ones that use \( \texttt{d} \): mdl.addConstrs(y[j,k]<= quicksum(d[(i,k)]*x[(i,j)]for i in N) for j in lot for k in G)mdl.addConstrs(quicksum(d[(i,k)]*x[(i,j)] f...

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    • Eli Towle
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  • Eli Towle commented,

    1. Community
    2. Modeling
    3. Infeasibility while adding a constraint

    Can you share a mathematical formulation of this model? Additionally, it would be helpful to see a complete, self-contained code example that reproduces the results you currently see. Here are some...

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    • Eli Towle
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  • Eli Towle commented,

    1. Community
    2. Programming
    3. Constraint comparing Var with one entry of MVar

    Starting with Gurobi 9.5, indexing an MVar like \( \texttt{x[j]} \) should yield a Var object, not an MVar object. Which version of Gurobi are you using? You can check with import gurobipy as gppri...

  • Eli Towle commented,

    1. Community
    2. Systems
    3. New Academic License Key

    Hi Tivon, Can you please request a separate academic license for your new computer? To do so, follow the instructions for a named-user academic license on the Academic Program and Licenses page. Eli

  • Eli Towle commented,

    1. Community
    2. Modeling
    3. binary programming for 0/m instead of 0/1 variables

    So now the problem becomes min(x'Qx-c'x), s.t. x=mz, z = 0 or 1, 0=<m<=2 (2 for instance), right? Does it mean that x, z, m are all variables to solve now? If so, should the Q and c in my objectiv...

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