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I ran a relaxed MIP and got some integer results; how can I constrain MIP to match those integers?

Suppose I run a relaxation of an MIP. If my result is all integers, I have achieved the same min/max that the MIP would achieve. However, what can I say if some portion of my result is integer? If half my decision variables come out integer, does…
Brannon
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Why are several of the decision variables zero at the corner point of a polytope?

I have the following equational Linear Program: \begin{align}\max&\quad c^T x\\\text{s.t.}&\quad Ax=b\\&\quad x\ge0\end{align} The matrix $A$ is $m\times n$, where $m\le n$, $c\in \mathbb{R}^n, x \in \mathbb{R}^n$ and $b\in\mathbb{R}^m$. Also the…
watchdogs132
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MILP - quantify magnitude of overlap

I'm building a manufacturing line optimization model. Part of the model is (lightly) penalizing running the line on the weekend. With time in minutes and t=0 representing 12:00:01 am Monday, the weekend begins at t=7200 (end of 5 days, start of…
Ralph Asher
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Using CBC CLI Arguments in Pyomo

I am currently using the cbc solver with Pyomo opt = SolverFactory('cbc') opt.solve(model) How can more options for Cbc be used, such that what we run using Pyomo is similar to: cbc -cuts off -strong 0 -preprocess off -heuristic off -solve
Athena Wisdom
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Interpretation of a subtour elimination constraint in the TSP

I have a problem with understanding the following mathematical model of the TSP. Given that the TSP is: $$\min \sum_{i,j\in N} d_{i,j} \cdot x_{i,j}$$ subjected to: $$\begin{array}{rrrr}\sum_{j\in N}x_{i,j}&=&1&\forall i \in N\\\ \sum_{i\in…
Snowflake
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Data structures for branch and bound: Efficiently finding the branch node vs. efficiently fathoming

I am implementing a branch and bound algorithm for the knapsack program that is essentially identical to the one described here. I am trying to decide on the optimal data structure to store the set of candidate nodes. It seems there are two natural…
Max
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TSPs and VRPs in real world

I have a CS background, I took some optional courses in Optimization. I stumbled upon classic transport problems like TSP and VRP. Maybe I am not familiar with the domain, but I think that there aren't a lot of software apps built around those…
SomeThoughts
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Can the primal Simplex Method walk all optima in linear time?

It's typical that the Simplex Method implementation exits once it finds an optimum value. However, if I want to find all optima that exist at extreme points (not those that exist along a face), is it possible to walk through them in linear time? In…
Brannon
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List of Call for papers

Is there somewhere a list of ongoing Call for papers for special issues in OR journals? I believe that such a list would not only create a good overview for publication opportunities but also inform about current research trends in the field.
PeterD
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Combining Multiple Cost Values in Shortest Path Problem

I am trying to solve a shortest path problem through Dijkstra's algorithm. However in my case, cost between nodes (nodes $i$ and $j$) are more than one- two nodes are compared based on two different properties and this results in two different cost…
Monotros
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is prime? in Operations Research

Is there a way to linearize is prime? in Operations Research? is prime(n) being true if $n$ is a prime number or false otherwise. If it is not possible, which I suspect, is there any other way in either: Non linear programming Constraint…
JKHA
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how can I modify my LP to activate the most constraints possible?

Suppose I have a linear program (LP) that has many optimal solutions. Of those optima, I want to find the optimum that activates (aka, "pegs" or "bumps") the largest number of constraints. Is there a general mechanism to achieve this? I was able to…
Brannon
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Does this game that I invented correspond to a valid optimization problem?

Recently, I thought of the following "game" that I would like to frame as an optimization problem: Assume there are five baskets. The first basket has five discrete objects (e.g., apples), the second basket has three discrete objects (e.g.,…
stats_noob
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Problem is infeasible with Gurobi, feasible with cbc (but can't access objective value)

I am solving a MILP with cbc and gurobi (via pyomo). Gurobi states that the model is infeasible. As to cbc the solver status states that a feasible and optimal solution is found, but then it fails to access the value of the objective (which in turn…
Meth
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Real Life Applications of Linear Programming

I am trying to find some real life ("non trivial") examples of Linear Programming. So far, most of the examples that I come across are from introductory textbooks involving some basic example about farmers choosing between different crops to grow…
stats_noob
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