DefaultFourierTransformFactory.java :  » UnTagged » android-tachometer » org » teneighty » fft » Android Open Source

/*
 * $Id$
 *
 * Copyright (c) 2006 Fran Lattanzio
 * 
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 * 
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 * 
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */

package org.teneighty.fft;

import java.util.Collections;
import java.util.List;

import org.teneighty.fft.algorithms.CooleyTukeyFastFourierTransform;
import org.teneighty.fft.algorithms.CooleyTukeyRadixTwoFastFourierTransform;
import org.teneighty.fft.algorithms.PrimeFactorFastFourierTransform;
import org.teneighty.fft.algorithms.DirectFourierTransform;
import org.teneighty.fft.factor.Factorization;
import org.teneighty.fft.factor.Factorization.Factor;
import org.teneighty.fft.factor.DefaultFactorization.DefaultFactor;


/**
 * The default fourier transform factory.
 *
 * @author Fran Lattanzio
 * @version $Revision$ $Date$
 */
public class DefaultFourierTransformFactory
  extends FourierTransformFactory
{

  
  /**
   * Constructor.
   */
  public DefaultFourierTransformFactory()
  {
    super();
  }
  

  /**
   * Create a good fourier transform for the specified factorization.
   * 
   * @param fact the factorization.
   * @return FourierTranform a new transform.
   * @throws NullPointerException If <code>fact</code> is <code>null</code>.
   * @throws IllegalArgumentException If fact is malformed.
   */
  @Override
  protected FourierTransform getTransformImpl( final Factorization fact )
    throws IllegalArgumentException, NullPointerException
  {
    List<Factor> facts = fact.getFactors();
    Factor first = facts.get( 0 );

    // get base.
    final int base = first.getBase();
    final int pow = first.getPower();

    if( facts.size() == 1 )
    {
      if( base == 1 )
      {
        return( new DirectFourierTransform( base ) );
      }      
      else if( base == 2 )
      {
        // use special radix two.
        return ( new CooleyTukeyRadixTwoFastFourierTransform( first.getTotal() ) );
      }
      else if( pow == 1 )
      {
        // it's prime - use prime selector!
        return( PrimeSelector.getFourierTransform( base ) );
      }
      else
      {
        // we have repeated factors - need to use mixed-radix CT.
        // create new factors...
        Factor one = new DefaultFactor( base, 1 );
        Factor two = new DefaultFactor( base, ( pow - 1 ) );

        // use mixed-radix cooley tukey.
        return ( new CooleyTukeyFastFourierTransform( Collections.singletonList( two ), Collections.singletonList( one ), first.getTotal() ) );        
      }
    }
    
    // use PFA.
    final int fsm1 = facts.size() - 1;
    return( new PrimeFactorFastFourierTransform( facts.subList( 0, fsm1 ), facts.subList( fsm1, facts.size() ), fact.getNumber() ) );
  }
  

}