objectivefunction.java

著名IT公司ILog的APS高级排产优化引擎

package com.power.lpsolver.LPSolve;
import java.util.*;
/**
 *
 * <p>Title: PIPE Engine</p>
 * <p>Description: Global Planning Optimization Engine</p>
 * <p>Copyright: Copyright (c) 2002</p>
 * <p>Company: Paraster, Inc.</p>
 * @author Wei Tan
 * @version 1.0
 */

/**
 * ObjectiveFunction is a special kind of constraint in that it has a sense
 * property (MAX or MIN). The default sense is MIN. Also ObjectiveFunction
 * has operations different from a constraint.
 */
public class ObjectiveFunction extends Constraint
{
        /**
         * The sense of the ObjectiveFunction, may only be MAX or MIN.
         */
    private String _sense;

        /**
         * class constructor, sense is initialized.
         * @param sense the sense of the ObjectiveFunction.
         */
	public ObjectiveFunction( String sense ) {
		super( "Objective Function", -1 );

		_sense = sense;
		//setRHS( 0 );
		setSign( "=" );
	}

        /**
         * class constructor, also default constructor.
         */
	public ObjectiveFunction() {
		super( "Objective Function", 0 );
		//setRHS( 0 );
		setSign( "=" );
	}

	public void addElement( Element elem ) {
		_conElements.put( _memMgr.getIntegerString( elem.getColumnNumber() ),
						  elem );
	}

        /**
         * Sets the sense of the ObjectiveFunction.
         * @param str the sense to be set.
         */
	public void setSense( String str ) {
		_sense = str;
	}

        /**
         * Tests to see if current solution is optimal.
         * @return <code>true</code> when all coefficients are greater than zero;
         *         <code>false</code> otherwise.
         */
	public boolean isOptimal() {
		Enumeration allElems = super.getElements().elements();
		Hashtable basicVariables = Solve.getInstance().getBasicVariables();
		MemoryManager memMgr = MemoryManager.getInstance();

		while( allElems.hasMoreElements() ) {
			Element elem = (Element) allElems.nextElement();


			Object obj = basicVariables.get( memMgr.getIntegerString( elem.getColumnNumber() ) );
			if( null != obj ) {
				continue;
			}

			if( elem.getCoefficient() < 0 ) return false;

		}

		return true;
	}

        /**
         * Gets the pivotal column number - the column with the most negative
         * coefficient.
         * @return the found column number;
         *         -1 when none exists.
         */
	public int getPivotColumn() {
		Solve solve = Solve.getInstance();
		Hashtable basicVariables = solve.getBasicVariables();
		Enumeration allElems = super.getElements().elements();
		MemoryManager memMgr = MemoryManager.getInstance();

		double mostNegative = 0;
		int colIdx = -1;

		while( allElems.hasMoreElements() ) {
			Element elem = (Element) allElems.nextElement();
			double coeff = elem.getCoefficient();
			//System.out.println( "coeff = " + coeff );
			if( coeff >= 0 ) continue;

			//must be nonbasic variable
			Object obj = basicVariables.get( memMgr.getIntegerString( elem.getColumnNumber() ) );
			if( null != obj ) {
				continue;
			}

			//get most negative
			if( coeff < mostNegative ) {
				mostNegative = coeff;
				colIdx = elem.getColumnNumber();

			}
		}
		//System.out.println("returned colidx  " + colIdx );
		return colIdx;
	}

        /**
         * Sets up Phase I objective function with a given constraint - replaces
         * an artificial variable in the objective function using a constraint
         * that contains the artificial variable.
         * con: sum(rest) + artVar = b may be rewritten as
         * con: artVar = b - sum(rest).
         * @param con a constraint that contains an artificial variable.
         */
	public void setupPhaseOneObjWithConstraint( Constraint con ) {
		Enumeration allElems = con.getElements().elements();

		while( allElems.hasMoreElements() ) {
			Element elem = (Element) allElems.nextElement();
			Element alreadyInObj = (Element) getElementAt( elem.getColumnNumber() );

			if( null == alreadyInObj ) {
				alreadyInObj = (Element) elem.clone();
				alreadyInObj.applyMultiplier( -1 );
				this.addElement( alreadyInObj );
			} else {
				alreadyInObj.addCoefficient( -1, elem );
			}
		}

		setRHS( getRHS() - con.getRHS() );

		eliminateFloatingError();
	}

	public String getMPSRowType() {
		return new String( " N  " );
	}

	public void print() {
		System.out.print( "\n" + "Min" + ": " );
		Enumeration allElems = this.getElements().elements();
		ModelVariables mdlVars = Model.getInstance().getModelVariables();

		while( allElems.hasMoreElements() ) {
			Element elem = (Element) allElems.nextElement();
			Variable var = mdlVars.getVariable( elem.getColumnNumber() );
			if( elem.getCoefficient() > 0 ) {
				System.out.print( " + " );
			} else {
				System.out.print( " - " );
			}
			System.out.print( Math.abs( elem.getCoefficient() ) );
			System.out.print( var.getMPSName() );
		}

		System.out.print( ";\n" );
	}

}