// ******************************************************************************
   //
   // Title:       Force Field X.
   // Description: Force Field X - Software for Molecular Biophysics.
   // Copyright:   Copyright (c) Michael J. Schnieders 2001-2024.
   //
   // This file is part of Force Field X.
   //
   // Force Field X is free software; you can redistribute it and/or modify it
  // under the terms of the GNU General Public License version 3 as published by
  // the Free Software Foundation.
  //
  // Force Field X is distributed in the hope that it will be useful, but WITHOUT
  // ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
  // FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
  // details.
  //
  // You should have received a copy of the GNU General Public License along with
  // Force Field X; if not, write to the Free Software Foundation, Inc., 59 Temple
  // Place, Suite 330, Boston, MA 02111-1307 USA
  //
  // Linking this library statically or dynamically with other modules is making a
  // combined work based on this library. Thus, the terms and conditions of the
  // GNU General Public License cover the whole combination.
  //
  // As a special exception, the copyright holders of this library give you
  // permission to link this library with independent modules to produce an
  // executable, regardless of the license terms of these independent modules, and
  // to copy and distribute the resulting executable under terms of your choice,
  // provided that you also meet, for each linked independent module, the terms
  // and conditions of the license of that module. An independent module is a
  // module which is not derived from or based on this library. If you modify this
  // library, you may extend this exception to your version of the library, but
  // you are not obligated to do so. If you do not wish to do so, delete this
  // exception statement from your version.
  //
  // ******************************************************************************
  package ffx.numerics.fft;
  
  import static org.junit.Assert.assertEquals;
  import static org.junit.Assert.assertTrue;
  
  import java.util.Arrays;
  import java.util.Collection;
  import java.util.Random;
  
  import ffx.utilities.FFXTest;
  import org.junit.Test;
  import org.junit.runner.RunWith;
  import org.junit.runners.Parameterized;
  import org.junit.runners.Parameterized.Parameters;
  
  /** @author Michael J. Schnieders */
  @RunWith(Parameterized.class)
  public class ComplexTest extends FFXTest {
  
    private final int n;
    private final String info;
    private final boolean preferred;
    private final double[] data;
    private final double[] orig;
    private final double[] dft;
  
    public ComplexTest(String info, int n, boolean preferred) {
      this.info = info;
      this.n = n;
      this.preferred = preferred;
      data = new double[n * 2];
      orig = new double[n * 2];
      dft = new double[n * 2];
      Random r = new Random();
      for (int i = 0; i < n; i++) {
        double d = r.nextDouble();
        data[i * 2] = d;
        orig[i * 2] = d;
      }
    }
  
    @Parameters
    public static Collection<Object[]> data() {
      return Arrays.asList(
          new Object[][] {
              {"Test n = 162 with factors [6, 3, 3, 3]", 162, true},
              {"Test n = 160 with factors [5, 4, 4, 2]", 160, true},
              {"Test n = 120 with factors [6, 5, 4]", 120, true},
              {"Test n = 64 with factors [4, 4, 4]", 64, true},
              {"Test n = 48 with factors [6, 4, 2]", 48, true},
              {"Test n = 21 with factors [7, 3]", 21, true},
              {"Test n = 38 with factors [2, 19]", 38, false},
              {"Test n = 22 with factors [2, 11]", 22, false},
          });
    }
  
    /** Test of fft method, of class Complex. */
    @Test
    public void testFft() {
      double tolerance = 1.0e-11;
  
      int offset = 0;
     int stride = 2;
     Complex complex = new Complex(n);
 
     // System.out.println(info + "\n Factors " + Arrays.toString(complex.getFactors()));
 
     long dftTime = System.nanoTime();
     Complex.dft(data, dft);
     dftTime = System.nanoTime() - dftTime;
     String dftString = " DFT Time: " + dftTime * 1.0e-9 + " s\n";
 
     long fftTime = System.nanoTime();
     complex.fft(data, offset, stride);
     fftTime = System.nanoTime() - fftTime;
     String fftString = " FFT Time: " + fftTime * 1.0e-9 + " s";
 
     // Test the FFT is equals the DFT result.
     for (int i = 0; i < 2 * n; i++) {
       assertEquals(" Forward " + info + " at position: " + i, dft[i], data[i], tolerance);
     }
 
     // The FFT is faster than the DFT.
     String message = fftString + dftString;
     // assertTrue(message, fftTime < dftTime);
 
     // Test that X = IFFT(FFT(X)).
     complex.inverse(data, offset, stride);
     for (int i = 0; i < n; i++) {
       double orig = this.orig[i * 2];
       double actual = data[i * 2];
       assertEquals(" IFFT(FFT(X)) " + info + " at position: " + i, orig, actual, tolerance);
     }
   }
 
   /** Test of preferredDimension method, of class Complex. */
   @Test
   public void testPreferredDimension() {
     boolean result = Complex.preferredDimension(n);
     assertEquals(info, preferred, result);
   }
 }