/**
 *  file :  SortPerf.java
 *  desc :  Sort performance benchmarking
 */

import Timer.*;
import java.util.Random;
import java.io.*;

class SortPerf {

  private static final String outFilename = "select.dat";
  private static final int    incN = 5;
  private static final int    maxN = 175;
  private static final int    numTrials = 200;

  /**
   *  post :  Opens the output file `outFilename' (above).
   *          Times a sorting algorithm on data for arrays
   *          of size incN, 2*incN, ..., maxN and writes
   *          the timing data to the output file.
   *
   *          For an array of each size, sorts the random
   *          data numTrials times to get an average
   *          running time per trial.
   */
  public static void main( String[] argv ) throws IOException {

    /* open the output file */
    PrintWriter timings = openOutputFile( outFilename );

    // print a header on the output file
    timings.println( "# Results for " + numTrials + " trials" );
    timings.println( "# n   time (msec)" );
    timings.println( "# ---------------" );

    /* do the timing */
    Timer stopWatch = new Timer();
    for( int n = incN; n <= maxN; n += incN ) {

      System.out.println( "timing n == " + n + " ... " );

      stopWatch.reset();
      for( int t = 0; t < numTrials; t++ ) {
	int[] data = randomData( n );
	stopWatch.start();

        /* Call the appropriate sorting routine here */
	SelectionSort.sort( data );

	stopWatch.stop();
      }
      long totalTime = stopWatch.elapsed();

      // output
      timings.println( n + "  " + totalTime );
    }

    /* fin! */
    timings.close();
    System.out.println( "done!  results in `" + outFilename + "'" );
  }


  /**
   *  post :  prints the contents of A to standard out
   */
  private static void printData( int[] A ) {
    for( int i = 0; i < A.length - 1; i++ ) {
      System.out.print( A[i] + ", " );
    }

    if( A.length-1 >= 0 )
      System.out.println( A[A.length-1] );
  }

  private static final long INIT_SEED = 1234567;

  /**
   *   pre :  n > 0
   *
   *  post :  returns an array of `n' randomly selected
   *          integers.
   */
  private static int[] randomData( int n ) {

    // choose same sequence of random numbers so that
    // we can fairly compare our sorting algorithms

    Random randGen = new Random( INIT_SEED );

    int[] newData = new int[ n ];
    for( int i = 0; i < n; i++ ) {
      newData[i] = randGen.nextInt();
    }

    return newData;
  }

  /**
   *  post :  returns an output file stream corresponding
   *          to the file given by `filename'
   */
  private static PrintWriter openOutputFile( String filename )
    throws IOException {
    return new PrintWriter( new FileOutputStream(filename) );
  }
}

// eof