Limbo.Parsers.LpParser

Table of Contents

• Introduction
• Examples
  • Flex/Bison Parser
  • All Examples
• References

Introduction

LP format is among the various file format to describe optimization problems. The parser can read a special case of linear programming problem in the LP format compatible to Gurobi, which contains only differential constaints. The special linear programming problem can be solved by dual min-cost flow algorithm in the Limbo.Solvers package. Here is a sample file.

Minimize
 b_5829890_x2
 + b_5880854_x2
Subject To
 - 2 b_5829890_x2 + 2 b_5829890_x1 <= -64
b_5880854_x2 - b_5880854_x1 >= 32
Bounds
b_5829890_x1 >= 10 
10 >= b_5880854_x1 
1014 <= b_5829890_x2 <= 1917
1014 <= b_5880854_x2 <= 1917
Generals 
b_5829890_x2 b_5880854_x2
Binary
b_5829890_x1
End

Examples

Flex/Bison Parser

See documented version: test/parsers/lp/test_bison.cpp

 
#include <iostream>
#include <fstream>
 
#include <limbo/parsers/lp/bison/LpDriver.h>
 
using std::cout;
using std::cin;
using std::endl;
using std::string;

class LpDataBase : public LpParser::LpDataBase
{
    public:
        typedef LpParser::int64_t int64_t;
        LpDataBase()
        {
            cout << "constructing LpDataBase" << endl;
        }
        void add_variable(string const& vname, double l, double r) 
        {
            cout << l << " <= " << vname << " <= " << r << endl;
        }
        void add_constraint(string const& cname, LpParser::TermArray const& terms, char compare, double constant) 
        {
            cout << cname << ": ";
            for (LpParser::TermArray::const_iterator it = terms.begin(); it != terms.end(); ++it)
                cout << " + " << it->coef << " " << it->var; 
            cout << " " << compare << " " << constant << endl; 
        }
        void add_objective(bool minimize, LpParser::TermArray const& terms)
        {
            if (minimize)
                cout << "Minimize\n"; 
            else 
                cout << "Maximize\n";
            for (LpParser::TermArray::const_iterator it = terms.begin(); it != terms.end(); ++it)
                cout << " + " << it->coef << " " << it->var; 
            cout << endl; 
            cout << "Subject To\n";
        }
        void set_integer(string const& vname, bool binary)
        {
            if (binary)
                cout << vname << ": BINARY\n";
            else 
                cout << vname << ": INTEGER\n";
        }
};

void test1(string const& filename)
{
    cout << "////////////// test1 ////////////////" << endl;
    LpDataBase db;
    LpParser::read(db, filename);
}

void test2(string const& filename)
{
    cout << "////////////// test2 ////////////////" << endl;
    LpDataBase db;
    LpParser::Driver driver (db);
    //driver.trace_scanning = true;
    //driver.trace_parsing = true;
 
    driver.parse_file(filename);
}

int main(int argc, char** argv)
{
    if (argc > 1)
    {
        test1(argv[1]);
        test2(argv[1]);
    }
    else 
        cout << "at least 1 argument is required" << endl;
 
    return 0;
}

Compiling and running commands (assuming LIMBO_DIR is exported as the environment variable to the path where limbo library is installed)

g++ -o test_bison test_bison.cpp -I $LIMBO_DIR/include -L $LIMBO_DIR/lib -llpparser
./test_bison benchmarks/problem.lp

All Examples

• test/parsers/lp/test_bison.cpp

References

• limbo/parsers/lp/bison/LpDataBase.h
• limbo/parsers/lp/bison/LpDriver.h