# All Questions

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54 views

### Optimize probability parameter in an optimal control problem

We have a game with infinite but countable rounds. We have one machine, that may either break down, or continue operating. For each round the machine operates, it gives cost $-1$ (so profit of $1$). ...
117 views

### Protein folding and protein design relation

I understand from active COVID-19 question Are there any COVID-19 (coronavirus) related optimization problems with input datasets that we can "crowd solve"? that protein folding problem is ...
2k views

### Does there exist an aggregation of videos on optimization?

Is there a website or otherwise maintained list of talks regarding mathematical optimization? This would be a big help for the community it seems. I'm most interested in those relating to integer ...
79 views

157 views

### Ways to strengthen QCQP relaxations

I was wondering what types of methods can be used to strengthen QCQP relaxations. Our solver has all the standard stuff, like constraint propagation, presolving, etc., but some QCQP problems seem to ...
102 views

### Optimal way to ensure optional intervals are consecutive in OR-Tools

I am trying to solve a scheduling problem in OR-Tools. There are lots of "events" that need to be scheduled to "blocks" (essentially half-days). I am naturally using optional intervals for the events. ...
56 views

### Pyomo CBC 1.#j error

I am using to solve my model Pyomo/CBC combination. But rarely, CBC Gap shows 1.#j and pyomo generate an error. Hence, it doesn't get solution. How can I solve this problem? Screen output: ...
53 views

### How to set combined stop condition in AMPL/CPLEX?

I would like to set a stop condition combined of a timelimit and a relative MIP gap. So I would like AMPL/CPLEX to look for the solution of my LP for an hour and if there isn't a solution stop if or ...
85 views

### How can I model this binary logic?

I am looking for a constraint to express the following: IF W1 = 0 AND W2 = 0 THEN Y = 0 IF W1 = 0 AND W2 = 1 THEN Y = 1 IF W1 = 1 AND W2 = 0 THEN Y = 0 IF W1 = 1 AND W2 = 1 THEN Y <= 1 ...
6k views

### Are there any COVID-19 (coronavirus) related optimization problems with input datasets that we can “crowd solve”?

Is anyone aware of a medicine/vaccine related challenges with a good problem definition and some available input datasets, ideally related to COVID-19? What kind of constraint solving challenges would ...
197 views

### How can this be expressed as a MILP constraint?

I am looking for a constraint to express the following: IF W1 = 0 AND W2 = 0 THEN Y = 1 IF W1 = 0 AND W2 = 1 THEN Y = 1 IF W1 = 1 AND W2 = 0 THEN Y = 0 IF W1 = 1 AND W2 = 1 THEN Y <= 1 ...
148 views

### Cutting-planes application procedure for a specific problem

Sort of following up with this question. I reformulated another model to make it convex and possibly solve it with some cut generation method. I would like to double-check whether I am doing it ...
81 views

### Linear programming sensitivity analysis using Matlab

I have a linear program in the MPS file format listing all the rows, columns, right-hand sides, etc. I can read that in Matlab and solve it using linprog. However, it seems there is no easy way to do ...
270 views

### if-else condition for the objective variable using big M notation

Let $0\leq \beta\leq 1$ be an objective variable. The size of $\beta$ is $N\!\times\!N$. Now, how can I impose the following? if $\beta_{i,j}>0$ then $\beta_{j,i}=0$ Big M notation can be ...
172 views

### How to represent multiple elements of the same set correctly?

In a mathematical model, I have a set $J$ of distinct jobs, and a constraint dealing with pairs of elements from the job set. Which of the following is the most accurate way to address two jobs $j$ ...
68 views

### Dealing with a non-convex problem

I have the following objective function. The variables: $h_p$, $e_{trs}\left(h_p\right), w_{trs}\left(h_p\right)$ are all non-negative continuous. $T,R,S,\pi_{trs}$ are polynomially-sized sets. All ...
Given a set $S$ which we need to travel following TSP rules. I was wondering if this sub tour elimination method is good enough or not? Let $b_{i,j}$ denote edge from $i$ to $j$ is taken or not and \$...