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Questions tagged [operations-research]

Operations Research is the application of quantitative techniques to decision making, typically involving mathematical optimization. Problems include dynamic programming, linear programming and Integer programming & discrete optimization.

Operations Research is the application of quantitative techniques to decision making, typically involving mathematical optimization. A problem is modeled as a math formulation, and the solution obtained via a solver. Problems in OR include dynamic programming, linear programming and Integer programming and discrete optimization.

The other names for Operations Research (OR) include Decision Science, Management Science, or Operational Research.

The Wikipedia page on Operations Research. INFORMS, the society for OR practitioners has a lot of relevant information.

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Monster heads problem in Python

Two guns A and B need to be used to kill a monster(with N heads). When gun A is used it cuts 6 heads, but if the monster doesn't die(no of heads > 0), it will grow 3 heads. When gun B is used it cuts 4 heads but if the monster doesn't die it grows 2…
user507220
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Analyzing the log of CBC solver in pulp

I am trying to solve an optimization problem in pulp using the CBC solver. Here is the log and few questions that I would like to know from the logs : Welcome to the CBC MILP Solver Version: 2.9.9 Build Date: Aug 21 2017 command line -…
function
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Clustering of sites using OR tools (CP solver)

I am trying to make clusters of sites based on their distance from each other. I am using or tools cp solver to achieve this. The program runs fine for 40 to 50 number of sites but when i try to run for about 200 sites with each cluster containing…
zxcv
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CPLEX changing the time limit

I am using and running directly from the IBM ILOG CPLEX Optimization Studio to solve an optimization problem. Since the problem and the instance is so big, CPLEX takes a very long time, so I want to limit the runtime to 2 hours. In parameters, the…
Taya Or
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how can I minimize the price/weight in a solver? (gurobi)

I have an optimization problem that consists of reducing the price/weight of the shipping of the products as much as possible. I modeled as below: MATHEMATICAL MODEL Basically, I have a vector called order, which represents the weight of each order…
Fernanda Almeida
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Python Gurobi Minimizing Cost: Code has no errors but doesnt find sensibel solution?

I wrote a code in Gurobi Python API for minimizing production costs which have a variable and a fixed cost part. There are a number of tasks which are assigned to a number of stations whereby cycle time should not be exceeded. Also 4 types of…
Harun Gül
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AddBoolOr and AddImplication in cp_sat solver

Hi I have difficulty understand the following code, can anyone help to explain? Thanks in advance! model.AddBoolOr(x, y.Not(), b) model.AddImplication(b, x) model.AddImplication(b, y)
Mark Spencer
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Get Objective Value from Pyomo every X iterations?

Is there a way to get from pyomo a list of the objective values at every X iterations, especially when using cbc? The usual way of running the solver only returns the final solver results. results =…
gameveloster
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Tips for fast first feasible solution of a MILP using scip

I have a MINLP problem. I can solve it quite fast (seconds) for small instances using SCIP. However, in big instances, it takes a long long time (hours) in getting to a feasible solution. I wanted to know if anyone here has some tips on how to reach…
orpanter
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What Discrete Optimization family is this?

I am given N lists of M items that will be physically realized (someone actually has to put items (names abbreviated here,) in physical bins.) Then the bins are emptied, if necessary, and re-used, working left-to-right. There is a real cost to…
klausnrooster
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Which mathematical optimization problem is this?

I have an combinational optimization problem and I do not know its name in literature. My problem is the following: I have n sets containing exclusive elements, so each element is present only in a set. An element is characterized by 2 constraints…
Max
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Can I set the SCIP constraint handler to work only after a feasible solution is found?

I read the SCIP constraint handler documentation, and reads that CONSHDLR_CHECKPRIORITY= -1 makes that the constraint handler only works when the solution is integral. However, my handler is still adding constraints before finding a feasible…
orpanter
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What are the options for CBC solver in Pyomo?

Two questions: 1- Is there any options for cbc solver to stop when a feasible solution is found? I know there is a opt.options['seconds'] =100 but when I specify small numbers it does not find a feasible one 2- Is there any list for CBC options ? so…
Optimization team
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Changing a parameter while branching in SCIP

I use pyscipopt. I know how to add constraints while branching using handlers (kind of), but now I also want to change some parameters. I imagine that is similar, but couldn’t found an example. What I want is as follows: -Every time a feasible node…
orpanter
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Efficiently solving assignment problem with constraints

I have a variation of https://en.wikipedia.org/wiki/Assignment_problem#Unbalanced_assignment: A bipartite graph with vertex sets A and T, Non-negative costs on the edges, All vertexes in A and T must occur at most once in a matching. But with…
Luma
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