PhpMIP is a PHP class representing a Linear Mixed-Integer Programm.
It comes with a writer to the IBM CPLEX LP file format and a base writer and Interface that should facilitate adding your own writer classes.
The package can be installed into your project via composer:
$ php composer.phar require i4h/php-mip "*"
See the examples directory for two examples MIPs.
The workflow follows that of common modeling languages:
- Create sets
- Create variables
- Create constraints
- Define the objective function
This is the example from example/trivial.php:
$mip = new \vendor\i4h\PhpMIP\MIP();
/* Variable x */
$mip->addVariable("x", \vendor\i4h\PhpMIP\MIPvariable::TYPE_CONTINUOUS);
$mip->setVariableLB("x", 0);
/* Variable y */
$mip->addVariable("y", \vendor\i4h\PhpMIP\MIPvariable::TYPE_CONTINUOUS);
$mip->setVariableLB("y", 0);
/* Objective (default coefficient is 1) */
$mip->addObjectiveCoefficient("x");
$mip->addObjectiveCoefficient("y");
/* Constraint x + y <= 1 */
$vars = [
['name'=>'x', 'coefficient'=>1],
['name'=>'y', 'coefficient'=>1],
];
$mip->addConstraintLE($vars, 1);
/* Use Lp writer to write to a file */
$writer = new \vendor\i4h\PhpMIP\LpWriter();
$writer->setOutFile("/path/to/outfile.lp");
$writer->write(create);
The code above will create an lp file with the following content:
Minimize
obj: 1 x + 1 y
Subject To
1 x + 1 y <= 1
Bounds
end