Top new questions this week:
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I have a MILP model that solves a master production schedule including capacity decisions. In the model I have a production quantity that should either be 0 or at least the amount that can be produced ...
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I’m not sure if I’m wording this right but in a nutshell, my problem is:
I’m modelling potential actions a boat owner can do to their boat. Let’s say he wants to know over the 50 year lifespan of the ...
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I have an MINLP problem to solve where I was initially using 'ipopt' solver but the solution was not sticking to 'binary/boolean/integer' domain type for a variable. I am not sure which free solver ...
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I am reading from Nonlinear Programming by Bertsekas, and in the section on ADMM, he says:
Consider the problem
$$\text{min} \sum _{i=1} ^ m f_i(x)$$
$$\text{s.t. }x \in \cap _{i = 1}^m X_i,$$
where $...
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Let's make a space for ALL of OR to be discussed. I'm particularly interested in the link between OR and design, I also co-chair the PSM SIG for the OR Society. Hopefully by putting in some tags we ...
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Nowadays, mathematical programming solvers have been frequently used to solve lots of practical/academic problems. Many of these might be interpreted as a MIP or MINLP to represent a specific problem (...
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I have two different MILP formulations for the same scheduling problem with the same complexity but with different running times. Why it is recommended to compare the relaxed versions of each ...
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Greatest hits from previous weeks:
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I find it hard to form math models for real life operations research problems, how can I learn this? Any books, tutorials available?
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Background
A while ago my team was implementing an interior point LP solver and we came across the following conundrum:
Is there a polynomial-time algorithm to find a feasible starting point
in ...
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Suppose we have two binary variables $x$ and $y$. How can we linearize the product $xy$?
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For the TSP there famously is the concord solver (http://www.math.uwaterloo.ca/tsp/concorde.html) which is argubly the fastest exact solver for the TSP.
There are many other problems that also show ...
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Suppose that you have two algorithms for solving an optimization model, and you want to benchmark their performance over a large set of instances (with only one performance metric, for example, the ...
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Many abbreviations are used in Operations Research. For example, we have abbreviations for problem classes (LP, MIP), solution methods (IPM), and specific problems (TSP, VRP).
Which abbreviations are ...
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So I noticed, that a lot of students taking OR-classes come from non-computer science backgrounds (e.g. buissiness administration). They typically had only one other class in their first semester ...
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Can you answer these questions?
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Let $\mathbf{A}=\left(a_{ij}\right)$ be a $n\times J$ matrix with $a_{ij}\geq 0$, $n>J$ and such that no row or column has all its entries equal to zero. Let also $\mathbf{k}=\left(k_j\right)$ be a ...
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Let $ x \in \mathbb{R}^n_+$ be a variable such that $\sum_{i=1}^n x_i = 1$. In other words, $x$ is in a probability simplex. I am working on barrier-like functions in nonconvex optimization over such ...
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