LEMON Tutorial  59
lp_demo.cc File Reference

Demo program for the LP solver interface. More...

`#include <iostream>`
`#include <lemon/lp.h>`

## Detailed Description

This demo program shows how the LEMON LP solver interface can be used. A simple linear programming (LP) problem is formulated and solved using the default LP solver (e.g. GLPK).

/* -*- mode: C++; indent-tabs-mode: nil; -*-
*
* This file is a part of LEMON, a generic C++ optimization library.
*
* Egervary Jeno Kombinatorikus Optimalizalasi Kutatocsoport
* (Egervary Research Group on Combinatorial Optimization, EGRES).
*
* Permission to use, modify and distribute this software is granted
* provided that this copyright notice appears in all copies. For
* precise terms see the accompanying LICENSE file.
*
* This software is provided "AS IS" with no warranty of any kind,
* express or implied, and with no claim as to its suitability for any
* purpose.
*
*/
#include <iostream>
#include <lemon/lp.h>
using namespace lemon;
int main()
{
// Create an instance of the default LP solver class
// (it will represent an "empty" problem at first)
Lp lp;
// Add two columns (variables) to the problem
// Add rows (constraints) to the problem
lp.addRow(0 <= 2 * x1 + x2 <= 25);
// Set lower and upper bounds for the columns (variables)
lp.colLowerBound(x1, 0);
lp.colUpperBound(x2, 10);
// Specify the objective function
lp.max();
lp.obj(5 * x1 + 3 * x2);
// Solve the problem using the underlying LP solver
lp.solve();
// Print the results
if (lp.primalType() == Lp::OPTIMAL) {
std::cout << "Objective function value: " << lp.primal() << std::endl;
std::cout << "x1 = " << lp.primal(x1) << std::endl;
std::cout << "x2 = " << lp.primal(x2) << std::endl;
} else {