fxsimplex 2.0.1

index.js

Source:
Author:
  • Michael.R.Fox, Ph.D. <fox.michael.r@gmail.com>
Copyright:
  • Michael R. Fox, Ph.D., 2020, 2021
License:
  • MIT Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the 'Software'), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sub-license, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions: - The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software: THE SOFTWARE IS PROVIDED 'AS IS', WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. *

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fxSimplex is a small JavaScript library designed to perform linear optimization using either the one-phase or two-phase simplex methods as appropriate.

Installation

To install, issue the following command:

npm install -l fxsimplex --save

Usage

Include fxSimplex in your project in one of two ways:

You can include a reference to the built version of the library:

<!DOCTYPE Html>
  <html>
      <head>
          <body>
              <script type = 'text/javascript' src = 'fxSimplex.min.js'></script>
              .
              <!--   or   -->
              .
              <script type = 'text/javascript' src = 'https://cdn.jsdelivr.net/npm/fxsimplex@latest/dist/fxSimplex.min.js'></script>
              .
          </body>
      </head>
  </html>

Or you may use ES6 syntax:

import simplex from 'node_modules/fxsimplex';

if you use this option note that the source files are ES6 modules (unlike the distribution files which have been transpiled). In this case, if you need to support older browsers you may want to edit your .babelrc file to specifically transpile fxSimplex:

{
     "exclude": "/node_modules\/(?!fxsimplex)/"
}

fxSimplex exposes only one method: simplex() which takes two arguments, an objective and an array of constraints. The objective must be a string in the form of Maximize Z = 1x + 5y. The objective must start with the word Maximize or Minimize (case is irrelevant and max or min is fine too) and be followed by the variable name for the objective function, an equals sign, and a function to be optimized.

The constraints are an array of strings in the in the form of ['x + y <= 4', '2x - y <= 7', ...]. Variables may be any combination of letters and numbers or character strings (such as 'x0', 'y1', 'q', etc.) as long as they start with a letter and don't use the reserved variable syntax of 's0', 'e0', 'a0'. These are reserved for slack, extra, and alternate variables respectively. However, variables may start with the letters s, e, and a as long as they don't follow the reserved variable syntax (i.e., a number immediately following the first letter). Constraints must contain a function which uses either '<=', '>=', or '='.

fxSimplex returns an object with the solution (an array of key value pairs for the basic variables and their coefficients in the form of [['y', 10],['x', 10], ['Z', 20]], ...) and a result: a string in the form of ['solved' | 'infeasible' | 'unbounded' | 'multiple solutions']. If the optimization is successful, the result will be either solved or multiple solutions, and the solution will contain optimal coefficients. If the result returns infeasible or unbounded, the optimization has failed and the coefficients returned in the solution will reflect the final tableau reached and not be optimal.

If the constraints or objective are in the incorrect format, an error to the console will be logged and fxSimplex will return an empty object {solution: [], result: ''}`.

Example

import simplex from 'fxsimplex';

     let objective = 'Maximize Z = 3x + 2y';
     let constraints = ['2x + y <= 18',
                        '2x + 3y <= 42',
                        '3x + y <= 24'];

    console.log(simplex(objective, constraints));

...

output: {
        solution: [['y', 12], ['s2',3], ['x',3], ['Z', 33]],
        result: 'solved'};