# Questions tagged [dual]

The tag has no usage guidance.

23 questions
Filter by
Sorted by
Tagged with
1 vote
120 views

### Dual to Primal conversion

I recently tried to solve a primal minimization problem using its maximization dual. In the optimal simplex tableau of the dual, there was a slack variable and only one dual variable in the basis. So, ...
1 vote
71 views

### Termination criterion for the Phase 1 algorithm in column generation

To initialize column generation, I obtain a feasible set of columns via the following Phase 1 algorithm. The restricted master problem for this algorithm is formulated as follows. min ...
• 615
1 vote
85 views

### The dual values and change in the variables values

For a constraint as Ax <= b, the dual shows the change in the objective function if the RHS increases by 1 unit. Now my question is that how we can determine how the optimal values will change by 1 ...
• 400
119 views

### Dual of a LP with a variable restricted to be negative

I have to find the dual of following LP: Minimize $x_1 + x_2 + x_3$ subject to $4x_1 + 8x_2 \geq3$ $7x_2 + 4x_3 \leq 6$ $3x_1 - 2x_2 + 5x_3 = 7$ $x_1 \leq 0, x_2 \geq 0, x_3$ is unrestricted I ...
• 1
419 views

### Understanding reduced costs and dual values

I have a headache regarding calculating the reduced costs of a linear program. I am using Pulp for modelling and CBC for solving. What I do is, I model a linear programming problem based on a rhs ...
• 1,143
134 views

### How to find robust counterpart of sum of logit functions?

Suppose function $\mu_i(y):\mathbb{R} \rightarrow \mathbb{R}$ is a logit function, $\mu_i(y)=1/(1+\exp(-y))$. Also, we assume that $\mathbf{x}_i\in \mathbb{R}^d$ and $\theta \in \mathbb{R}^d$. I am ...
• 2,160
378 views

### CPLEX stuck in solve method - dual simplex solved model

I am solving a (rather large) MILP in CPLEX in Java. I also wrote a solution extractor method, which works most of the time. However, when CPLEX tries to solve my problem with the dual simplex method ...
• 29
1 vote
67 views

### Developing the dual model

I have the following linear program: $$\min \sum_{\vec{s} \in S} \sum_{\vec{z} \in \Xi_{\vec{s}}} c(\vec{s}, \vec{z}) \times \chi(\vec{s}, \vec{z}) \label{eqADP4}$$ \...
• 615
1 vote
67 views

### Dual of a quadratic constraint

This is my model. \begin{align} \min_x&\quad\sum_{e\in E} X_e p_e \\ \text{s.t.}&\quad\sum_{e \in E: T(e)=i} X_e - \sum_{e \in E: H(e)=i} X_e = \begin{cases}1, \;\text{if}\;i=s\\-1,\;\text{if}...
• 517
1 vote
157 views

### Help with dual of a problem

Could anyone confirm me if I write the correct dual for my problem? The different sets confuse me a lot. $s$ is the source node and $t$ the sink node. I'm uncertain if the last dual constraint in ...
• 517
67 views

### Dual of the alternative solutions

Suppose we have two alternative solutions for a linear program. Are their corresponding dual solutions the same? (in terms of the values for each dual variable)
• 400
342 views

### Finding the dual problem of a minimum problem

How to convert the following primal problem into its dual problem: \begin{align} \min_{x,z}&\quad a^\top x + b^\top z\\\text{s.t.}&\quad Ax-d \le Cz \\&\quad x\ge 0, z \le 0. \end{align} I ...
• 131
242 views

### Electricity market clearing price using fixed-MIP formulation?

Dual information of electricity markets clearing problem is required to calculate the marginal clearing price. As most electricity market problems are based on MIP (and dual information of MIP is not ...
• 189
2k views

### Is optimal solution to dual not unique if optimal solution to the primal is degenerate?

If optimal solution to the primal is degenerate, does it necessarily follow that optimal solution to dual not unique? That is, is uniqueness an unnecessary assumption? Spin-off from here. In my ...
• 59
425 views

### Derive "true" shadow price for degenerated LPs using commercial solvers (e.g. Gurobi)

In linear programming for an optimal primal degenerate solution the values of the dual variables are in general not identical with the corresponding shadow prices. Several proposals on how to find the ...
• 93
70 views

### Deriving KKT Conditions for time-step equations

I have a variable $e(h)$, and below is the part of the Lagrangian equation where I am taking the derivative with respect to $e(h)$. \frac{\partial }{\partial e(h)} \hspace{.2cm}\mu_1(h)(e(h)-\bar{E}...
• 803
1k views

### Physical Interpretation of a dual of an LP

I was recently asked to physically interpret a dual of an LP for an audience who does not know mathematics/OR (without LP, dual, bounds, etc.). Though I attempted it and was very close to what the ...
147 views

### On dual-formulation of a given primal for a set-covering problem

I need to solve an LP-relaxation of an airline crew pairing optimization problem (CPOP). The problem formulation is a modified SCP and is as follows: Primal of the CPOP: \begin{align}\min&\quad\...
153 views

### Dual variables associated with same equation for different time instants

I have three equations that are essentially the same equation defined for three time instants. The equations are basically calculating the state of energy of an energy storage facility. \begin{align} ...
• 803
46 views

### Derivations for two formulae for obtaining optimal dual variable values from the optimal primal tableau

We're being taught Industrial Engineering and Operations Research for the first time this semester. Referring to the book by Hamdy A. Taha, I noticed the mention of two formulae for swiftly obtaining ...
90 views

### KKT conditions validation- one dual variable equating to two values

I have the following optimization problem: \begin{alignat}2\min &\quad A(t)\cdot x(t)-B(t)\cdot y(t)+C(t)\cdot z(t)-D(t)\cdot k(t)\\\text{s.t.}&\quad z(t)+z_1(t)-y(t)-y_1(t)+x(t) = k(t);&...
• 803
178 views

### Finding Dual Objective

I have the following simplified optimization problem: \begin{align}\max &\quad ax+by\\\text{s.t.}&\quad0 \le x \le \overline X\\&\quad0 \le y \le\overline Y\\&\quad z = E-x+\beta\cdot ...
• 803