Questions tagged [linear-programming]

Questions on linear programming, the optimization of a linear function subject to linear constraints.

A linear programming problem may be defined as the problem of maximizing or minimizing a linear function subject to linear constraints. The constraints may be equalities or inequalities.

Linear programs are problems that can be expressed in canonical form as \begin{align}\max\quad&c^\top x\\\text{s.t.}\quad& Ax\le b\\\quad& x\ge 0\end{align} where $x$ represents the vector of variables (to be determined), $c$ and $b$ are vectors of (known) coefficients, $A$ is a (known) matrix of coefficients, and ${\displaystyle (\cdot )^{\top}}$ is the matrix transpose.

The expression to be maximized or minimized is called the objective function ($c^{\top}x$ in this case).

The inequalities $Ax \le b$ and $x \ge 0$ are the constraints which specify a convex polytope over which the objective function is to be optimized. The inequality $x \ge 0$ is called non-negativity constraints and are often found in linear programming problems. The other inequality $Ax \le b$ is called the main constraints.

Applications:

Linear programming can be applied to various fields of study. It is widely used in mathematics, and to a lesser extent in business, economics, and for some engineering problems. Industries that use linear programming models include transportation, energy, telecommunications, and manufacturing. It has proven useful in modeling diverse types of problems in planning, routing, scheduling, assignment, and design.

References:

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Linear programming with schedule overlap

I've got a linear programming problem like this: There is a set of projects. each project has a duration in months, and a number of employees required each project must begin on a given month (1..12) there is a total of N employees Not all…
Gaston
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How to solve this LP problem graphically?

Max Z = $10x + 15y$ s.t. $x \ge 400$ $x + y \le 1000$ $0.7x - 0.3y \ge 0$ $x,y \ge 0$ The first two constraints I understand how to graph, but how do I do the third one? How do I graph this inequality? Thanks in advance.
Hikato
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Linear Optimization - Putting gaps between scheduled items?

I'm playing around with linear programming for schedule optimization, and I'm using ojAlgo although that shouldn't matter. The scenario is I have several university classes each with variables start time S and end time E. Assume there is only one…
tmn
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Basic feasible solutions

I am not able to understand the part "without solving show that it has an optimal solution" Please help. Thanks P.S: Question in attachment ]1
AJ_
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Comparison between MILP and LP solver performance.

In case of a problem which can be formulated as both MILP or LP, which is more appropriate. Factors into the consideration can be time complexity of solving algorithm, stability and convergence issues and any other as well.
Parikshit
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Looking for examples of simplex tableaus

(a) Such that the LPP is unbounded and thus has no optimal solutions. (b) Such that the tableau represents an optimal solution to the LPP. Just looking to get some examples of these, to familiarize and figure out how to come up with them in the…
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Why do we call one LP a primal, and one a dual? Would switching what we call them make a difference?

If I've been given a problem that tells me that a certain LP1 is a primal, and it's dual is LP2.. Could I also say that LP2 is the primal, and LP1 is it's dual? Why do we call one a primal and one a dual? The weak duality theorem states that the…
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Linear programming standard form convention: RHS positive?

Indeed many authors have various versions of standard form LP problems, but I am wondering if the following is an essential trait: In an LP problem we have min(f(x)) with constraint,say, $Ax\geq b$. My question is whether the RHS has to be positive…
Thomas Kojar
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Linear programming constraint specification

How do you specify a linear constraint to an integer program where, given a binary variable x over a period of t intervals (x1,x2…xt), you want x to be =1 either never or at least n consecutive times?
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Linear programming - Maximizing negative objective function

How can I turn this into canonical form and then use the two-phase simplex method to solve it? Would I need to add slack variable AND surplus variables? $$\max\quad -2x_1-x_2-x_3 \\ \text{subject to: }-x_1-x_3 \le -1 \\ -x_1+x_2 \le -2 \\ -x_2+x_3…
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Convert a Non-Linear Constraint of Integer and continuous variables to a Linear Constraint

(Updated) I am looking to simplify formulation of a MINLP problem with below formulation- Objective Function - $$min (\sum_{i=1}^n x_i), x_i \in I, x_i>=0 $$ Below are the constraints - $$\sum_{i=1}^n (x_i * y_i) = C_1 , y_i \in [0,1], y_i>=0…
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What are the necessary and sufficient conditions for having multiple optimal solutions of a LP?

The necessary condition is found to be degeneracy at the presence of more than one leaving variable is essential for multiple optimal solutions. But what is the sufficient condition? Is $C-C_b*inv(B)*A=0$ is sufficient one? Also if one has one…
Parikshit
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Do we need the extra column in the augmented matrix of a LP?

Consider the following linear program: $$ \begin{array}{ll} \text{maximize} & x_1 + x_2 + x_3 \\ \text{subject to} & 60x_1 + 20x_2 +50x_3 \leq 1 \\ & 20x_1 + 50x_2 + 10x_3 \leq 1 \\ \text{and} & x_1, x_2, x_3 \geq 0 \end{array} $$ It has the…
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Linear program feasible region is infinite with optimum solution of bounded cost

Is there an example of linear program in two variables that has infinite feasible region with an optimum solution of bounded cost?
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Linear Programming question- optimal solution

A film producer is seeking actors and investors for his new movie. There are n available actors; actor i charges $s_i$ dollars. For funding, there are m available investors. Investor j will provide $p_j$ dollars, but only on the condition that…
Rheem
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