table.java

Create a problem solver for linear programming

/*
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 */

package ro.simplex;

import ro.utils.Fraction;

/**
 *
 * @author Doan Chien Thang
 */
public class Table {
    private Dictionary dict;
    private ProblemInStandardForm problem;

    public Table(Dictionary dict, ProblemInStandardForm problem) {
        this.dict = dict;
        this.problem = problem;
    }

    @Override
    public String toString() {
        String result = "";
        return result;
    }

    public Variable getOutVar() {
        Variable resVar = null;
        Variable outVar = null;
        Fraction minCoef = new Fraction(0);
        Objective objective = this.dict.getObjective();
        if (objective.hasPositiveCoefs()) {
            for (int i = 0; i < objective.getCoefs().size(); i++) {
//            for (int i = objective.getCoefs().size() - 1; i >= 0; i--) {
                Variable inVar = null;
                if (objective.getCoefs().get(i).getOpposite().isNegative()) {
                    outVar = objective.getVars().get(i);
                    inVar = getInVar(outVar);
                    if (inVar == null) {
                        outVar = null;
                        continue;
                    }
                    if (objective.getCoef(outVar).isGreaterThan(minCoef)) {
                        resVar = outVar;
                        minCoef = objective.getCoef(outVar);
                    }
                }
            }
            if (resVar == null)
                this.problem.answer = Problem.IS_UNBOUND;
        } else {
            this.problem.answer = Problem.HAS_ONE_SOLUTION;
            for (int i = 0; i < objective.getCoefs().size(); i++)
                if (this.problem.baseVars.contains(objective.getVars().get(i))
                && objective.getCoefs().get(i).equals(new Fraction(0))) {
                    this.problem.answer = Problem.HAS_INFINITVE_SOLUTIONS;
                    break;
                }
        }
        return resVar;
    }
    
    public Variable getInVar(Variable outVar) {
        Fraction f = new Fraction(0);
        Variable var = null;
        for (int i = 0; i < dict.getVarConstraints().size(); i++) {
        //for (int i = dict.getVarConstraints().size() - 1; i >= 0; i--) {
            Fraction coef = dict.getVarConstraints().get(i).getCoef(outVar);
            if (coef.isNegative() && f.isGreaterThan(Fraction.divide(coef,
                    dict.getVarConstraints().get(i).getValue()))) {
                var = dict.getVarConstraints().get(i).getLeftVar();
                f = Fraction.divide(coef,
                        dict.getVarConstraints().get(i).getValue());
            }
        }
        return var;
    }
}