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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Counting in Linear Programming

I have a linear programming question I have integer values t[i] such that |t[i]| < M. Each T[i] is a positive or negative integer bound by a known maximum I'd like to set a value c[i] such that c[i] is zero if t[i] <> 0 How do I do this? The more…
Nickle
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Are these linear programming constraints correct?

The problem is: Beth works a maximum of $20$ hours/week programming computers and tutoring math. She receives $\$25$/hour for programming and $\$20$/hour for tutoring. She works between $3$ and $8$ hours/week programming, but always gives more time…
Someone
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Why are the constraints X and Y in fractions?

I got a question about a LP problem. Truckco manufactures two types of trucks: 1 and 2. Each truck must go through the painting shop and assembly shop. If the painting shop were completely devoted to painting Type 1 trucks, then 800 per day could…
Hikato
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Consider the LPP $ \ Ax \leq b , \ \ x \geq 0 \ $ having $ \ infeasible \ $ solution and $ b \geq 0 \ $.

Consider the LPP $ \ Ax \leq b , \ \ x \geq 0 \ $ having $ \ infeasible \ $ solution and $ b \geq 0 \ $. We then start $ Phase \ I $ of the Simplex method by working with an Auxiliary problem in the following form: $ Max \ \ -x_0 \\ Subject \ \…
MAS
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What is the objective function and constraints of this problem?

How to solve this problem? This is what I know so far. Let A be the no. of drivers at the beginning of the year. Let B be the no. of drivers fired. Let C be the no. of drivers recruited Is the objective function 12000A + 2000B + 1000C Am I on the…
Janice
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LP Maximising a negative objective function

How can I turn this into canonical form and then use the two-phase simplex method to solve it? $$max\quad -2x_1-x_2-x_3 \\ \text{subject to: }-x_1-x_3 \le -1 \\ -x_1+x_2 \le -2 \\ -x_2+x_3 \le -1 \\ x_1,x_2,x_3 \ge 0 $$ When I put it into the…
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Is there a proof of complementary slackness that doesn't use strong duality?

I'm trying to prove strong duality using complementary slackness, not the other way around. But for that I need to prove complementary slackness without using strong duality first. Does anybody know of such a proof?
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A faster method to solve l.p.p. problems.

The following question was asked in an exam: Consider the problem: Maximize $2y_1+3y_2+5y_3+4y_4$ subject to $y_1+y_2\leq 1,$ $y_2+y_3\leq 1,$ $y_4+y_1\leq 1,$ $y_3+y_4\leq 1$ and $y_i\geq 0$ for i=1,2,3,4. Then the optimum value is 1. equal to…
shwetha
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Master and Subproblem for Column Generation Algorithm

Let $S$ be a set of vectors defined as $S := \{x \in \mathbb{R}^n_+ : e^Tx = 1\}$. A vectorization of matrix $xx^T$, denoted by $vec(xx^T)$, is a transformation by stacking the columns of $xx^T$ on top of each other, resulting a column vector.…
FarahFai
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Turning a linear program into an auxiliary problem

I have maximise $$10x-2y+5z$$ s.t $$2x+y-z \le 3$$ $$-8x-2y+5z \le 2 $$ $$-x+2y-3z \ge 7$$ This becomes maximise $$10x-2y+5z$$ s.t $$2x+y-z +s_1= 3$$ $$-8x-2y+5z +s_2=3 2 $$ $$-x+2y-3z -s_1= 7$$ Now only the third constraint gives me an infeasible…
stackdsewew
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How to choose leaving variable when problem is unbounded

Online solver gave me that this problem was unbounded. $$Maximise − 7 + x − 2y + 3z − w_3$$ subject to $$w_1 = 3 − 2x − y + z$$ $$w_2 = 2 + 8x + 2y − 5z$$ $$w_0 = 7 − x + 2y − 3z + w_3$$ $$x, y, z, w_0, w_1, w_2, w_3 \ge 0$$ I can increase $x$ by…
stackdsewew
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Formulating a linear program

I can't figure out a geometric interpretation of what this question wants. I thought maybe it was akin to a line of best fit but I am not sure. An d $f(x_1)$ the value of the function at $x_1$, but isn't that the same as $y_1$, so wouldn't…
stackdsewew
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Need help to understand part of a lecture on linear programming

I am watching this video on 1:17:50 and I do not understand the statement that professor makes: why $yAx = cx = yb$ implies that every $x$ has the same objective, which means all $x$ are optimal. I do not really understand what David Karger is…
YohanRoth
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Verify my simple linear program formulation

Let $x_a$ denote amount of feed A and $x_b$ denote amount of feed B. Minimize $10x_a+12x_b$ subject to $4x_a+2x_b \ge 12$ $4x_a+8x_b \ge 24$ $8x_b \ge 8$ Have I got the numbers right? Also to solve it graphically I would get 3 lines that…
stackdsewew
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Conversion of absolute value LP to standard form

Minimize: $\mid{x-y}\mid + 2z$ Subject to: $0 \leq x \leq 3$, $0\leq y \leq 4$, $0 \leq z$, $-x+y \geq 4$, $x+y+z \leq 2$. The following is what I did, I am looking to see if this is correct, or if there is an easier way to go about it the…
Pascal
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