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4 votes
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How to increase the lower bound while solving a MILP model?

As mentioned in comments, a tight value for $M$ helps. Sometimes, redundant constraints can help the solver by giving it information that lets it generate bound-tightening cuts. As far as I know, this ...
prubin's user avatar
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0 votes

Unable to find good solution for CVRP with Time Window

Timefold Solver is an open source solver (Apache License) with a CVRPTW implementation (including a web UI) in our quickstarts. It supports Java, Kotlin and soon Python.
Geoffrey De Smet's user avatar
1 vote

PULP: Optimization Assignment of Bicycle production per month

For both Q1 and Q2, you need to enforce $y_i = 1 \implies x_i \ge 1$, which you can do via linear constraint $y_i \le x_i$. For Q1: Replace $15 x_C$ with $15(1 - 0.2 y_A y_H) x_C$ in the working ...
RobPratt's user avatar
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1 vote

Lexicographic objective to maximize the x-th highest value

As Mark L. Stone notes, some solvers (including CPLEX) handle lexicographic optimization directly. If you are using a solver that does not, but does allow you to modify branching, pruning etc. using ...
prubin's user avatar
  • 39.6k
0 votes

Minimize Expenses For Workers

Have $i$ be the set of days where $i=\{Mon, Tue, Wed, Thurs, Fri, Sat, Sun\}$. Additionally, let $j$ denote the quantity of drivers with $j=\{1,2,3,4,5,6\}$, have $k$ denote the range of workers where ...
Miss Mae's user avatar
  • 145
1 vote

Optimizing calls to a separation problem in branch and cut

As far as I understand, you have a branch-and-cut algorithm that separates valid inequalities for integer and fractional solutions. The cuts you separate are valid and improve the quality of the ...
Alberto Santini's user avatar
1 vote

Optimizing calls to a separation problem in branch and cut

Are you solving the separation problem inside a generic callback? If so, CPLEX will solve the problem once per call to the callback (or less, if the callback sometimes chooses not to solve the problem)...
prubin's user avatar
  • 39.6k

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