Site.java

/**
 *  Copyright 2007-2008 University Of Southern California
 *
 *  Licensed under the Apache License, Version 2.0 (the "License");
 *  you may not use this file except in compliance with the License.
 *  You may obtain a copy of the License at
 *
 *  http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing,
 *  software distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 */

package edu.isi.pegasus.planner.selector.site.heft;

import java.util.List;
import java.util.LinkedList;
import java.util.ListIterator;

/**
 * A data class that models a site as a collection of processors.
 * The number of processors can only be specified in the constructor.
 *
 * @author Karan Vahi
 * @version $Revision$
 */
public class Site {


    /**
     * The number of processors making up a site.
     */
    private int mNumProcessors;

    /**
     * A list of processors making up the site.
     */
    private List mProcessors;

    /**
     * The index to the processor that is to be used for scheduling a job.
     */
    private int mCurrentProcessorIndex;

    /**
     * The logical name assigned to the site.
     */
    private String mName;

    /**
     * The default constructor.
     *
     * @param name  the name to be assigned to the site.
     */
    public Site( String name ) {
        mName          = name;
        mNumProcessors = 0;
        mProcessors    = new LinkedList();
        mCurrentProcessorIndex = 0;
    }

    /**
     * The overloaded constructor.
     *
     * @param name  the name to be assigned to the site.
     * @param  num   the number of processors.
     */
    public Site( String name, int num ){
        mName          = name;
        mNumProcessors = num;
        mCurrentProcessorIndex = -1;
        mProcessors    = new LinkedList( );
    }


    /**
     * Returns the earliest time the site is available for scheduling
     * a job.  It is non insertion based scheduling policy.
     *
     * @param start     the time at which to start the search.
     *
     * @return long
     */
    public long getAvailableTime( long start ){
        int num = 0;

        //each processor is checked for start of list
        long result  = Long.MAX_VALUE;
        long current;
        ListIterator it;
        for( it = mProcessors.listIterator( ); it.hasNext(); num++ ){
            Processor p = ( Processor ) it.next();
            current     = p.getAvailableTime( start );
            if( current < result ){
                //tentatively schedule a job on the processor
                result = current;
                mCurrentProcessorIndex = num;
            }
        }

        if( result > start && num < mNumProcessors ){
            //tentatively schedule a job to an unused processor as yet.
            result = start;
            mCurrentProcessorIndex = num++;
            //if using a normal iterator
            //could use addLast() method
            it.add( new Processor () );

        }

        //sanity check
        if( result == Long.MAX_VALUE ){
            throw new RuntimeException( "Unable to scheduled to site" );
        }

        return result;
    }


    /**
     * Schedules a job to the site.
     *
     * @param start    the start time of the job.
     * @param end      the end time for the job
     */
    public void scheduleJob( long start, long end ){
        //sanity check
        if(  mCurrentProcessorIndex == -1 ){
            throw new RuntimeException( "Invalid State. The job needs to be tentatively scheduled first!" );
        }

        Processor p = ( Processor )mProcessors.get( mCurrentProcessorIndex );
        p.scheduleJob( start, end );

        //reset the index
        mCurrentProcessorIndex = -1;
    }


    /**
     * Returns the name of the site.
     *
     * @return name of the site.
     */
    public String getName(){
        return mName;
    }

    /**
     * Returns the number of available processors.
     *
     * @return number of available processors.
     */
    public int getAvailableProcessors( ){
        return this.mNumProcessors;
    }
}