A “Dual LP Calculator” is a tool used to solve dual linear programming (LP) problems. In linear programming, every problem has a corresponding dual problem that provides valuable insights into the original (primal) problem. Understanding and solving dual LP problems can help in various fields such as economics, resource allocation, and production planning.

## What is a Dual LP Calculator?

A Dual LP Calculator helps solve dual linear programming problems. Linear programming involves optimizing a linear objective function subject to a set of linear constraints. The dual problem is derived from the primal problem and provides a different perspective on the same scenario. The dual LP calculator makes this conversion and calculation process easier.

## Purpose and Functionality

The purpose of a Dual LP Calculator is to transform a primal LP problem into its dual form and solve it. This helps in understanding the properties of the original problem and can provide additional insights into optimal solutions. The calculator requires several inputs to work:

**Coefficients of the Objective Function (c)**: These are the coefficients from the primal problem’s objective function.**Constraint Coefficients (A)**: This matrix consists of the coefficients from the primal problem’s constraints.**Right-hand Side Values (b)**: These are the constants on the right-hand side of the inequality/equality constraints in the primal problem.

## Understanding Dual Linear Programming

In a primal problem, we typically minimize or maximize a linear objective function subject to constraints. The dual problem has its own objective function and constraints derived from the primal problem.

### Example of a Primal Problem

**Minimize** Z=c1x1+c2x2Z = c_1 x_1 + c_2 x_2Z=c1x1+c2x2

**Subject to:**

a11x1+a12x2≥b1a_{11} x_1 + a_{12} x_2 \ge b_1a11x1+a12x2≥b1

a21x1+a22x2≥b2a_{21} x_1 + a_{22} x_2 \ge b_2a21x1+a22x2≥b2

x1,x2≥0x_1, x_2 \ge 0x1,x2≥0

### Example of the Corresponding Dual Problem

**Maximize** W=b1y1+b2y2W = b_1 y_1 + b_2 y_2W=b1y1+b2y2

**Subject to:**

a11y1+a21y2≤c1a_{11} y_1 + a_{21} y_2 \le c_1a11y1+a21y2≤c1

a12y1+a22y2≤c2a_{12} y_1 + a_{22} y_2 \le c_2a12y1+a22y2≤c2

y1,y2≥0y_1, y_2 \ge 0y1,y2≥0

## Step-by-Step Calculation

### Inputs for the Calculator:

**Coefficients of the Objective Function (c)**: c1,c2c_1, c_2c1,c2**Constraint Coefficients (A)**: a11,a12,a21,a22a_{11}, a_{12}, a_{21}, a_{22}a11,a12,a21,a22**Right-hand Side Values (b)**: b1,b2b_1, b_2b1,b2

### Steps to Convert Primal to Dual:

**Objective Function of Dual**: The coefficients in the primal’s constraints (b values) become the coefficients in the dual’s objective function.**Constraint Coefficients for Dual**: The matrix transpose of the primal’s constraint matrix (A) becomes the constraint matrix in the dual.**Right-hand Side of Dual Constraints**: The coefficients from the primal objective function become the right-hand side constraints in the dual problem.

## Example Calculation

Given a primal problem:

**Minimize**Z=3×1+5x2Z = 3x_1 + 5x_2Z=3×1+5×2**Subject to:**2×1+3×2≥82x_1 + 3x_2 \ge 82×1+3×2≥84×1+x2≥64x_1 + x_2 \ge 64×1+x2≥6×1,x2≥0x_1, x_2 \ge 0x1,x2≥0

Convert to the dual problem:

**Maximize**W=8y1+6y2W = 8y_1 + 6y_2W=8y1+6y2**Subject to:**2y1+4y2≤32y_1 + 4y_2 \le 32y1+4y2≤33y1+y2≤53y_1 + y_2 \le 53y1+y2≤5y1,y2≥0y_1, y_2 \ge 0y1,y2≥0

## Information Table

Input | Value |
---|---|

Coefficients of Objective (c) | 3, 5 |

Constraint Coefficients (A) | [2, 3], [4, 1] |

Right-hand Side Values (b) | 8, 6 |

## Conclusion

A Dual LP Calculator is a valuable tool for simplifying and solving dual linear programming problems. By converting a primal problem to its dual form, it provides a different perspective that can offer deeper insights into the optimal solution. This tool is beneficial in many fields, including economics, resource allocation, and production planning, helping to understand system limits and potentials effectively.