Questions tagged [gurobi]

Questions related to the commercial solver Gurobi Optimizer.

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71 views

gurobipy.GurobiError: Second argument should be a list of Var

The following error was encountered when using LinExpr in gurobi: ...
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1answer
176 views

Job Shop Scheduling Problem: jobs are scheduled on the same machine at the same time

I want to solve a job shop scheduling problem. I got $n$ Jobs that have to be scheduled on $k$ Machines. A Job $i$ has 2 or 3 Tasks $j$, and there is a known sequence of the Tasks of a Job. One ...
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57 views

Hybrid metaheuristic and linear program?

I have a Linear program (LP) that can solve problem X with two objective functions a and b, I use the weighted sum method. I use Gurobi solver when I optimize the objective alone, the problem takes a ...
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61 views

How to use gurobi to plan production and minimize the times of changeovers

Suppose we have two lines: L1 and L2. Suppose we have 4 product types: A1, ...
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81 views

Multiple conditions in indicator constraint of Gurobi

I'm working on a vehicle routing problem, in which a vehicle need to pick up amounts of things in some nodes. I'm trying to solve it by Gurobi optimizer. Except for meeting the time windows of each ...
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76 views

How can I set the solution of gurobi to be a multiple of 10 instead of all integers?

For example, the solution for gurobi has two solutions, as follows: [10,20,50,70] [55,79,30,80] I only want to output solutions that contain only multiples of 10. The sample example as follow: ...
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78 views

Binary variable with two criteria in Gurobi (Java)

I have the following problem in Gurobi (Java). I have a binary variable $b$ that is supposed to be $1$ or $0$ depending on my optimisation variable $x$. It should be true that $b = 1$ if $c_1 \le x \...
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60 views

Quadratic optimization in Gurobi with constraint

I have a question of understanding in Gurobi: I have an objective function in which my optimization variable x is squared. I have solved this bsiher by a quadratic objective function with $x$, $x$. ...
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88 views

Strange Result from GurobiPy

I am trying to understand why GurobiPy gives me a strange result for a simple linear programming model coded as below? Why is the optimality gap is 0%? Please let me know if you spot any errors in the ...
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92 views

Expansion heuristic using gurobi reduced cost / shadow price (LP)

Gurobi 9.0.0 // C++ // LP Let us assume the following problem with three nodes: (1)-----(2)-----(3) node (1) is producing ...
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80 views

Ways to improve lower bounds while solving MIPs

What are the ways to improve lower bounds while solving a minimization problem (MILP)?
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86 views

Gurobi Environment should be Common or Unique for concurrent optimization problems?

Thanks for the amazing performance of Gurobi. Actually we are using Gurobi Cloud (via its python binding - Gurobipy) for our optimization requirements. Due to our ...
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174 views

How to write this constraint in Gurobi python?

I'm wondering how I can translate this math constraint to gurobi python. $$\forall a \in A, b \in B, x_{ab} \in \{0, 1\}$$ So far I have written: ...
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1answer
261 views

Gurobi: How to define constraints that can accept multiple different values? [duplicate]

I have a question about Gurobi. How do I define a constraint that can accept multiple different values? For example, a sample constraint is shown as follows: ...
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1answer
229 views

if-else query depending on optimization variable in Gurobi (Java)

I am looking for the most elegant solution to the following problem: I have an if-else query that depends on my optimization variable $x_i$. If $a \leq b_i + x_i$, the parameter $c$ should take the ...
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1answer
85 views

How to solve the following linear programming problem using Gurobi (or at least python)?

For an optional ungraded assignment (see it as a complex problem that won't be graded, more to test our skills and knowledge) I was given the following problem. It is not as straightforward as all the ...
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56 views

Lower bound very bad. How to improve?

I have the following MILP: \begin{alignat}{2} \nonumber \mbox{minimize } \quad & \phi = \sum_{i=1}^{m-1} \sum_{f=1}^{F} \sum_{\underset{\bar{f} \neq f}{\bar{f}=1}}^F \sum_{h \in H} \left( D_{f \...
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97 views

Problems with a MILP

I need some advice, any hints will be appreciated. I have a MILP and I am using Gurobi to solve it. I have a feasible integer solution. When I use mipstart, after ...
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96 views

Mixed Integer Programming - Model Formulation for A Resource Allocation Problem

There are a number of orders, which needs to be shipped. For each order, there may be 1 to 3 route options. The problem here is to find out the best allocation (combination) of orders among these ...
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44 views

Linear equation from pairs of values with conditions in Gurobi (Java)

How can I create a linear equation in Gurobi (Java) from values (x-y value pairs) that also has the following properties: $\forall x \leq 0 \Longrightarrow y = 0$ The linear line/equation should have ...

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