// ******************************************************************************
   //
   // Title:       Force Field X.
   // Description: Force Field X - Software for Molecular Biophysics.
   // Copyright:   Copyright (c) Michael J. Schnieders 2001-2025.
   //
   // 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 edu.rit.pj.IntegerForLoop;
  import edu.rit.pj.IntegerSchedule;
  import edu.rit.pj.ParallelRegion;
  import edu.rit.pj.ParallelTeam;
  
  import javax.annotation.Nullable;
  import java.util.Arrays;
  import java.util.Random;
  import java.util.logging.Level;
  import java.util.logging.Logger;
  
  import jdk.incubator.vector.DoubleVector;
  import jdk.incubator.vector.VectorShuffle;
  import jdk.incubator.vector.VectorSpecies;
  
  import static java.lang.String.format;
  import static java.util.Objects.requireNonNullElseGet;
  
  /**
   * Compute the 3D FFT of complex, double precision input of arbitrary dimensions via 1D Mixed Radix
   * FFTs in parallel.
   *
   * <p>The location of the input point [i, j, k] within the input array must be: <br>
   * double real = input[x*nextX + y*nextY + z*nextZ] <br>
   * double imag = input[x*nextX + y*nextY + z*nextZ + 1] <br>
   * where <br>
   * int nextX = 2 <br>
   * int nextY = 2*nX <br>
   * int nextZ = 2*nX*nY <br>
   *
   * @author Michal J. Schnieders
   * @see Complex
   * @since 1.0
   */
  public class Complex3DParallel {
  
    private static final Logger logger = Logger.getLogger(Complex3DParallel.class.getName());
    /**
     * The X-dimension.
     */
    private final int nX;
    /**
     * The Y-dimension.
     */
    private final int nY;
    /**
     * The Z-dimension.
     */
    private final int nZ;
    /**
     * The offset from any real value to its imaginary part.
     */
    private final int im;
    /**
     * The offset from any real value to the next real value (1 for blocked and 2 for interleaved).
     */
    private final int ii;
    /**
     * The offset to the next X value.
     */
   private final int nextX;
   /**
    * The offset to the next Y value.
    */
   private final int nextY;
   /**
    * The offset to the next Z value.
    */
   private final int nextZ;
   /**
    * The offset to the next X value for the transposed data.
    */
   private final int trNextX;
   /**
    * The offset to the next Y value for the transposed data.
    */
   private final int trNextY;
   /**
    * The offset to the next Z value for the transposed data.
    */
   private final int trNextZ;
   /**
    * The reciprocal space data.
    */
   private final double[] recip;
   /**
    * The number of threads to use.
    */
   private final int threadCount;
   /**
    * The ParallelTeam instance.
    */
   private final ParallelTeam parallelTeam;
   /**
    * The 2D FFTs for each thread for XY-planes.
    */
   private final Complex2D[] fftXY;
   /**
    * The 1D FFTs for each thread to compute FFTs along the Z-dimension.
    * Each thread operates one YZ-plane at a time to complete nY FFTs.
    */
   private final Complex[] fftZ;
   /**
    * The FFTs along the Z-dimension will use offset between real and imaginary parts.
    */
   private final int internalImZ;
   /**
    * The IntegerSchedule to use.
    */
   private final IntegerSchedule schedule;
   /**
    * The X-dimension minus 1.
    */
   private final int nXm1;
   /**
    * The Y-dimension minus 1.
    */
   private final int nYm1;
   /**
    * The Z-dimension minus 1.
    */
   private final int nZm1;
   /**
    * The FFTRegion for parallel calculation of a 3D FFT.
    */
   private final FFTRegion fftRegion;
   /**
    * The IFFTRegion for parallel calculation of an inverse 3D FFT.
    */
   private final IFFTRegion ifftRegion;
   /**
    * The ConvolutionRegion for parallel calculation of a convolution.
    */
   private final ConvolutionRegion convRegion;
   /**
    * This is a reference to the input array for convenience.
    * The input array must be of size 2 * nX * nY * nZ.
    */
   public double[] input;
   /**
    * Use SIMD instructions if available.
    */
   private boolean useSIMD;
   private final VectorSpecies<Double> species = DoubleVector.SPECIES_PREFERRED;
   private final int vectorSize = species.length();
   private final int[] shuffle = {0, 0, 1, 1, 2, 2, 3, 3, 4, 4, 5, 5, 6, 6, 7, 7};
   private final VectorShuffle<Double> expandFirstHalf = VectorShuffle.fromArray(species, shuffle, 0);
   private final VectorShuffle<Double> expandSecondHalf = VectorShuffle.fromArray(species, shuffle, vectorSize);
 
   /**
    * Pack the FFTs for optimal use of SIMD instructions.
    */
   private boolean packFFTs;
   private final boolean localZTranspose;
   /**
    * Work array used for transforms along the Z-axis.
    */
   public final double[] work3D;
 
   /**
    * Initialize the 3D FFT for complex 3D matrix.
    *
    * @param nX           X-dimension.
    * @param nY           Y-dimension.
    * @param nZ           Z-dimension.
    * @param parallelTeam A ParallelTeam instance.
    * @since 1.0
    */
   public Complex3DParallel(int nX, int nY, int nZ, ParallelTeam parallelTeam) {
     this(nX, nY, nZ, parallelTeam, DataLayout3D.INTERLEAVED);
   }
 
   /**
    * Initialize the 3D FFT for complex 3D matrix.
    *
    * @param nX           X-dimension.
    * @param nY           Y-dimension.
    * @param nZ           Z-dimension.
    * @param parallelTeam A ParallelTeam instance.
    * @param dataLayout   The data layout.
    * @since 1.0
    */
   public Complex3DParallel(int nX, int nY, int nZ, ParallelTeam parallelTeam, DataLayout3D dataLayout) {
     this(nX, nY, nZ, parallelTeam, null, dataLayout);
   }
 
   /**
    * Initialize the 3D FFT for complex 3D matrix.
    *
    * @param nX              X-dimension.
    * @param nY              Y-dimension.
    * @param nZ              Z-dimension.
    * @param parallelTeam    A ParallelTeam instance.
    * @param integerSchedule The IntegerSchedule to use.
    * @since 1.0
    */
   public Complex3DParallel(int nX, int nY, int nZ, ParallelTeam parallelTeam, @Nullable IntegerSchedule integerSchedule) {
     this(nX, nY, nZ, parallelTeam, integerSchedule, DataLayout3D.INTERLEAVED);
   }
 
   /**
    * Initialize the 3D FFT for complex 3D matrix.
    *
    * @param nX              X-dimension.
    * @param nY              Y-dimension.
    * @param nZ              Z-dimension.
    * @param parallelTeam    A ParallelTeam instance.
    * @param integerSchedule The IntegerSchedule to use.
    * @param dataLayout      The data layout.
    * @since 1.0
    */
   public Complex3DParallel(int nX, int nY, int nZ, ParallelTeam parallelTeam,
                            @Nullable IntegerSchedule integerSchedule, DataLayout3D dataLayout) {
     this.nX = nX;
     this.nY = nY;
     this.nZ = nZ;
     this.parallelTeam = parallelTeam;
     recip = new double[nX * nY * nZ];
 
     DataLayout1D dataLayout1D;
     DataLayout2D dataLayout2D;
     switch (dataLayout) {
       default:
       case INTERLEAVED:
         // Interleaved data layout.
         im = 1;
         ii = 2;
         nextX = 2;
         nextY = 2 * nX;
         nextZ = 2 * nX * nY;
         // Internal FFTs will be performed in interleaved format.
         dataLayout1D = DataLayout1D.INTERLEAVED;
         dataLayout2D = DataLayout2D.INTERLEAVED;
         // Transforms along the Z-axis will be repacked into 1D interleaved format.
         internalImZ = 1;
         trNextY = 2;
         trNextZ = 2 * nY;
         trNextX = 2 * nY * nZ;
         break;
       case BLOCKED_X:
         // Blocking is along the X-axis.
         im = nX;
         ii = 1;
         nextX = 1;
         nextY = 2 * nX;
         nextZ = 2 * nX * nY;
         // Internal FFTs will be performed in blocked format.
         dataLayout1D = DataLayout1D.BLOCKED;
         dataLayout2D = DataLayout2D.BLOCKED_X;
         // Transforms along the Z-axis will be repacked into 1D blocked format.
         internalImZ = nZ * nY;
         trNextY = 1;
         trNextZ = nY;
         trNextX = 2 * nY * nZ;
         break;
       case BLOCKED_XY:
         // Blocking is based on 2D XY-planes.
         im = nX * nY;
         ii = 1;
         nextX = 1;
         nextY = nX;
         nextZ = 2 * nY * nX;
         // Internal FFTs will be performed in blocked format.
         dataLayout1D = DataLayout1D.BLOCKED;
         dataLayout2D = DataLayout2D.BLOCKED_XY;
         // Transforms along the Z-axis will be repacked into 1D blocked format.
         internalImZ = nY * nZ;
         trNextY = 1;
         trNextZ = nY;
         trNextX = 2 * nY * nZ;
         break;
       case BLOCKED_XYZ:
         // Blocking is based on 3D XYZ-volume with all real values followed by all imaginary.
         im = nX * nY * nZ;
         ii = 1;
         nextX = 1;
         nextY = nX;
         nextZ = nY * nX;
         // Internal 1D FFTs will be performed in blocked format.
         dataLayout1D = DataLayout1D.BLOCKED;
         dataLayout2D = DataLayout2D.BLOCKED_XY;
         // Transforms along the Z-axis will be repacked into 1D blocked format.
         internalImZ = nY * nZ;
         trNextY = 1;
         trNextZ = nY;
         trNextX = 2 * nY * nZ;
         break;
     }
 
     nXm1 = this.nX - 1;
     nYm1 = this.nY - 1;
     nZm1 = this.nZ - 1;
     threadCount = parallelTeam.getThreadCount();
     schedule = requireNonNullElseGet(integerSchedule, IntegerSchedule::fixed);
 
     // Do not use SIMD by default for now.
     useSIMD = false;
     String simd = System.getProperty("fft.useSIMD", Boolean.toString(useSIMD));
     try {
       useSIMD = Boolean.parseBoolean(simd);
     } catch (Exception e) {
       useSIMD = false;
     }
 
     // Do not pack FFTs by default for now.
     packFFTs = false;
     String pack = System.getProperty("fft.packFFTs", Boolean.toString(packFFTs));
     try {
       packFFTs = Boolean.parseBoolean(pack);
     } catch (Exception e) {
       packFFTs = false;
     }
 
     String localTranspose = System.getProperty("fft.localZTranspose", "true");
     boolean local;
     try {
       local = Boolean.parseBoolean(localTranspose);
     } catch (Exception e) {
       local = true;
     }
     localZTranspose = local;
 
     fftXY = new Complex2D[threadCount];
     for (int i = 0; i < threadCount; i++) {
       fftXY[i] = new Complex2D(nX, nY, dataLayout2D, im);
       fftXY[i].setPackFFTs(packFFTs);
       fftXY[i].setUseSIMD(useSIMD);
     }
 
     fftZ = new Complex[threadCount];
     for (int i = 0; i < threadCount; i++) {
       fftZ[i] = new Complex(nZ, dataLayout1D, internalImZ, nY);
       fftZ[i].setUseSIMD(useSIMD);
     }
 
     if (localZTranspose) {
       work3D = null;
     } else {
       work3D = new double[2 * nX * nY * nZ];
     }
 
     fftRegion = new FFTRegion();
     ifftRegion = new IFFTRegion();
     convRegion = new ConvolutionRegion();
   }
 
   public String toString() {
     return "Complex3DParallel {" +
         "nX=" + nX +
         ", nY=" + nY +
         ", nZ=" + nZ +
         ", im=" + im +
         ", ii=" + ii +
         ", nextX=" + nextX +
         ", nextY=" + nextY +
         ", nextZ=" + nextZ +
         ", threadCount=" + threadCount +
         ", parallelTeam=" + parallelTeam +
         ", internalImZ=" + internalImZ +
         ", schedule=" + schedule +
         ", nXm1=" + nXm1 +
         ", nYm1=" + nYm1 +
         ", nZm1=" + nZm1 +
         ", fftRegion=" + fftRegion +
         ", ifftRegion=" + ifftRegion +
         ", convRegion=" + convRegion +
         ", useSIMD=" + useSIMD +
         ", packFFTs=" + packFFTs +
         '}';
   }
 
   /**
    * Use SIMD instructions if available.
    *
    * @param useSIMD True to use SIMD instructions.
    */
   public void setUseSIMD(boolean useSIMD) {
     this.useSIMD = useSIMD;
     for (int i = 0; i < threadCount; i++) {
       fftXY[i].setUseSIMD(useSIMD);
       fftZ[i].setUseSIMD(useSIMD);
     }
   }
 
   /**
    * Pack the FFTs for optimal use of SIMD instructions.
    *
    * @param packFFTs True to pack the FFTs.
    */
   public void setPackFFTs(boolean packFFTs) {
     this.packFFTs = packFFTs;
     for (int i = 0; i < threadCount; i++) {
       fftXY[i].setPackFFTs(packFFTs);
     }
   }
 
   /**
    * Compute the 3D FFT, perform a multiplication in reciprocal space,
    * and the inverse 3D FFT in parallel.
    *
    * @param input The input array must be of size 2 * nX * nY * nZ.
    * @since 1.0
    */
   public void convolution(final double[] input) {
     this.input = input;
     try {
       parallelTeam.execute(convRegion);
     } catch (Exception e) {
       String message = "Fatal exception evaluating a convolution.\n";
       logger.log(Level.SEVERE, message, e);
     }
   }
 
   /**
    * Compute the 3D FFT in parallel.
    *
    * @param input The input array must be of size 2 * nX * nY * nZ.
    * @since 1.0
    */
   public void fft(final double[] input) {
     this.input = input;
     try {
       parallelTeam.execute(fftRegion);
     } catch (Exception e) {
       String message = " Fatal exception evaluating the FFT.\n";
       logger.log(Level.SEVERE, message, e);
     }
   }
 
   /**
    * Get the timings for each thread.
    *
    * @return The timings for each thread.
    */
   public long[] getTiming() {
     return convRegion.getTiming();
   }
 
   /**
    * Compute the inverse 3D FFT in parallel.
    *
    * @param input The input array must be of size 2 * nX * nY * nZ.
    * @since 1.0
    */
   public void ifft(final double[] input) {
     this.input = input;
     try {
       parallelTeam.execute(ifftRegion);
     } catch (Exception e) {
       String message = "Fatal exception evaluating the inverse FFT.\n";
       logger.log(Level.SEVERE, message, e);
       System.exit(-1);
     }
   }
 
   /**
    * Initialize the timing array.
    */
   public void initTiming() {
     convRegion.initTiming();
   }
 
   /**
    * Get the timing string.
    *
    * @return The timing string.
    */
   public String timingString() {
     return convRegion.timingString();
   }
 
   /**
    * Setter for the field <code>recip</code>.
    *
    * @param recip an array of double.
    */
   public void setRecip(double[] recip) {
     // Reorder the reciprocal space data for convolution.
     // Input
     // trNextY = ii
     // trNextZ = nY*ii
     // real[y, z] = work[y*trNextY + z*trNextZ]
     // imag[y, z] = work[y*trNextY + z*trNextZ + internalImZ]
     int recipNextY = nX;
     int recipNextZ = nY * nX;
     int index = 0;
     for (int x = 0; x < nX; x++) {
       int dx = x;
       for (int z = 0; z < nZ; z++) {
         int dz = dx + z * recipNextZ;
         for (int y = 0; y < nY; y++) {
           int conv = y * recipNextY + dz;
           this.recip[index] = recip[conv];
           index++;
         }
       }
     }
   }
 
   /**
    * An external ParallelRegion can be used as follows: <code>
    * start() {
    * fftRegion.input = input;
    * }
    * run(){
    * execute(0, nZm1, fftRegion.fftXYLoop[threadID]);
    * execute(0, nXm1, fftRegion.fftZLoop[threadID]);
    * }
    * </code>
    */
   private class FFTRegion extends ParallelRegion {
 
     private final FFTXYLoop[] fftXYLoop;
     private final FFTZLoop[] fftZLoop;
     private final TransposeLoop[] transposeLoop;
     private final UnTransposeLoop[] unTransposeLoop;
 
     private FFTRegion() {
       fftXYLoop = new FFTXYLoop[threadCount];
       fftZLoop = new FFTZLoop[threadCount];
       for (int i = 0; i < threadCount; i++) {
         fftXYLoop[i] = new FFTXYLoop();
         fftZLoop[i] = new FFTZLoop();
       }
       if (!localZTranspose) {
         transposeLoop = new TransposeLoop[threadCount];
         unTransposeLoop = new UnTransposeLoop[threadCount];
         for (int i = 0; i < threadCount; i++) {
           transposeLoop[i] = new TransposeLoop();
           unTransposeLoop[i] = new UnTransposeLoop();
         }
       } else {
         transposeLoop = null;
         unTransposeLoop = null;
       }
     }
 
     @Override
     public void run() {
       int threadIndex = getThreadIndex();
       try {
         if (localZTranspose) {
           execute(0, nZm1, fftXYLoop[threadIndex]);
           execute(0, nXm1, fftZLoop[threadIndex]);
         } else {
           execute(0, nZm1, fftXYLoop[threadIndex]);
           execute(0, nXm1, transposeLoop[threadIndex]);
           execute(0, nXm1, fftZLoop[threadIndex]);
           execute(0, nZm1, unTransposeLoop[threadIndex]);
         }
       } catch (Exception e) {
         logger.severe(e.toString());
       }
     }
   }
 
   /**
    * An external ParallelRegion can be used as follows: <code>
    * start() {
    * ifftRegion.input = input;
    * }
    * run(){
    * execute(0, nXm1, ifftRegion.ifftZLoop[threadID]);
    * execute(0, nZm1, ifftRegion.ifftXYLoop[threadID]);
    * }
    * </code>
    */
   private class IFFTRegion extends ParallelRegion {
 
     private final IFFTXYLoop[] ifftXYLoop;
     private final IFFTZLoop[] ifftZLoop;
     private final TransposeLoop[] transposeLoop;
     private final UnTransposeLoop[] unTransposeLoop;
 
     private IFFTRegion() {
       ifftXYLoop = new IFFTXYLoop[threadCount];
       ifftZLoop = new IFFTZLoop[threadCount];
       for (int i = 0; i < threadCount; i++) {
         ifftXYLoop[i] = new IFFTXYLoop();
         ifftZLoop[i] = new IFFTZLoop();
       }
       if (!localZTranspose) {
         transposeLoop = new TransposeLoop[threadCount];
         unTransposeLoop = new UnTransposeLoop[threadCount];
         for (int i = 0; i < threadCount; i++) {
           transposeLoop[i] = new TransposeLoop();
           unTransposeLoop[i] = new UnTransposeLoop();
         }
       } else {
         transposeLoop = null;
         unTransposeLoop = null;
       }
     }
 
     @Override
     public void run() {
       int threadIndex = getThreadIndex();
       try {
         if (localZTranspose) {
           execute(0, nXm1, ifftZLoop[threadIndex]);
           execute(0, nZm1, ifftXYLoop[threadIndex]);
         } else {
           execute(0, nXm1, transposeLoop[threadIndex]);
           execute(0, nXm1, ifftZLoop[threadIndex]);
           execute(0, nZm1, unTransposeLoop[threadIndex]);
           execute(0, nZm1, ifftXYLoop[threadIndex]);
         }
       } catch (Exception e) {
         logger.severe(e.toString());
       }
     }
   }
 
   /**
    * An external ParallelRegion can be used as follows: <code>
    * start() {
    * convRegion.input = input;
    * }
    * run(){
    * execute(0, nZm1, convRegion.fftXYLoop[threadID]);
    * execute(0, nYm1, convRegion.fftZIZLoop[threadID]);
    * execute(0, nZm1, convRegion.ifftXYLoop[threadID]);
    * }
    * </code>
    */
   private class ConvolutionRegion extends ParallelRegion {
 
     private final FFTXYLoop[] fftXYLoop;
     private final TransposeLoop[] transposeLoop;
     private final FFTZIZLoop[] fftZIZLoop;
     private final UnTransposeLoop[] unTransposeLoop;
     private final IFFTXYLoop[] ifftXYLoop;
     private final long[] convTime;
 
     private ConvolutionRegion() {
       fftXYLoop = new FFTXYLoop[threadCount];
       fftZIZLoop = new FFTZIZLoop[threadCount];
       ifftXYLoop = new IFFTXYLoop[threadCount];
       convTime = new long[threadCount];
       for (int i = 0; i < threadCount; i++) {
         fftXYLoop[i] = new FFTXYLoop();
         fftZIZLoop[i] = new FFTZIZLoop();
         ifftXYLoop[i] = new IFFTXYLoop();
       }
       if (!localZTranspose) {
         transposeLoop = new TransposeLoop[threadCount];
         unTransposeLoop = new UnTransposeLoop[threadCount];
         for (int i = 0; i < threadCount; i++) {
           transposeLoop[i] = new TransposeLoop();
           unTransposeLoop[i] = new UnTransposeLoop();
         }
       } else {
         transposeLoop = null;
         unTransposeLoop = null;
       }
     }
 
     public void initTiming() {
       for (int i = 0; i < threadCount; i++) {
         fftXYLoop[i].time = 0;
         fftZIZLoop[i].time = 0;
         ifftXYLoop[i].time = 0;
       }
       if (!localZTranspose) {
         for (int i = 0; i < threadCount; i++) {
           transposeLoop[i].time = 0;
           unTransposeLoop[i].time = 0;
         }
       }
     }
 
     public long[] getTiming() {
       if (localZTranspose) {
         for (int i = 0; i < threadCount; i++) {
           convTime[i] = convRegion.fftXYLoop[i].time
               + convRegion.fftZIZLoop[i].time
               + convRegion.ifftXYLoop[i].time;
         }
       } else {
         for (int i = 0; i < threadCount; i++) {
           convTime[i] = convRegion.fftXYLoop[i].time
               + convRegion.transposeLoop[i].time
               + convRegion.fftZIZLoop[i].time
               + convRegion.unTransposeLoop[i].time
               + convRegion.ifftXYLoop[i].time;
         }
       }
       return convTime;
     }
 
     public String timingString() {
       StringBuilder sb = new StringBuilder();
       if (localZTranspose) {
         double xysum = 0.0;
         double zizsum = 0.0;
         double ixysum = 0.0;
         for (int i = 0; i < threadCount; i++) {
           double fftxy = fftXYLoop[i].getTime() * 1e-9;
           double ziz = fftZIZLoop[i].getTime() * 1e-9;
           double ifftxy = ifftXYLoop[i].getTime() * 1e-9;
           String s = format("  Thread %3d: FFTXY=%8.6f, FFTZIZ=%8.6f, IFFTXY=%8.6f\n",
               i, fftxy, ziz, ifftxy);
           sb.append(s);
           xysum += fftxy;
           zizsum += ziz;
           ixysum += ifftxy;
         }
         String s = format("  Sum       : FFTXY=%8.6f, FFTZIZ=%8.6f, IFFTXY=%8.6f\n",
             xysum, zizsum, ixysum);
         sb.append(s);
       } else {
         double xysum = 0.0;
         double transsum = 0.0;
         double zizsum = 0.0;
         double untranssum = 0.0;
         double ixysum = 0.0;
         for (int i = 0; i < threadCount; i++) {
           double fftxy = fftXYLoop[i].getTime() * 1e-9;
           double trans = transposeLoop[i].getTime() * 1e-9;
           double ziz = fftZIZLoop[i].getTime() * 1e-9;
           double untrans = unTransposeLoop[i].getTime() * 1e-9;
           double ifftxy = ifftXYLoop[i].getTime() * 1e-9;
           String s = format("  Thread %3d: FFTXY=%8.6f, Trans=%8.6f, FFTZIZ=%8.6f, UnTrans=%8.6f, IFFTXY=%8.6f\n",
               i, fftxy, trans, ziz, untrans, ifftxy);
           sb.append(s);
           xysum += fftxy;
           transsum += trans;
           zizsum += ziz;
           untranssum += untrans;
           ixysum += ifftxy;
         }
         String s = format("  Sum       : FFTXY=%8.6f, Trans=%8.6f, FFTZIZ=%8.6f, UnTrans=%8.6f, IFFTXY=%8.6f\n",
             xysum, transsum, zizsum, untranssum, ixysum);
         sb.append(s);
       }
 
       return sb.toString();
     }
 
     @Override
     public void run() {
       int threadIndex = getThreadIndex();
       try {
         if (localZTranspose) {
           execute(0, nZm1, fftXYLoop[threadIndex]);
           execute(0, nXm1, fftZIZLoop[threadIndex]);
           execute(0, nZm1, ifftXYLoop[threadIndex]);
         } else {
           execute(0, nZm1, fftXYLoop[threadIndex]);
           execute(0, nXm1, transposeLoop[threadIndex]);
           execute(0, nXm1, fftZIZLoop[threadIndex]);
           execute(0, nZm1, unTransposeLoop[threadIndex]);
           execute(0, nZm1, ifftXYLoop[threadIndex]);
         }
       } catch (Exception e) {
         logger.severe(e.toString());
       }
     }
   }
 
   private class FFTXYLoop extends IntegerForLoop {
 
     private Complex2D localFFTXY;
     private long time;
 
     @Override
     public void run(final int lb, final int ub) {
       for (int z = lb; z <= ub; z++) {
         int offset = z * nextZ;
         localFFTXY.fft(input, offset);
       }
     }
 
     @Override
     public IntegerSchedule schedule() {
       return schedule;
     }
 
     public long getTime() {
       return time;
     }
 
     public void finish() {
       time += System.nanoTime();
     }
 
     @Override
     public void start() {
       time -= System.nanoTime();
       localFFTXY = fftXY[getThreadIndex()];
     }
   }
 
   private class IFFTXYLoop extends IntegerForLoop {
 
     private Complex2D localFFTXY;
     private long time;
 
     @Override
     public void run(final int lb, final int ub) {
       for (int z = lb; z <= ub; z++) {
         int offset = z * nextZ;
         localFFTXY.ifft(input, offset);
       }
     }
 
     @Override
     public IntegerSchedule schedule() {
       return schedule;
     }
 
     public long getTime() {
       return time;
     }
 
     public void finish() {
       time += System.nanoTime();
     }
 
     @Override
     public void start() {
       time -= System.nanoTime();
       localFFTXY = fftXY[getThreadIndex()];
     }
   }
 
   private class FFTZLoop extends IntegerForLoop {
 
     private Complex localFFTZ;
     private long time;
     private final double[] work;
 
     private FFTZLoop() {
       if (localZTranspose) {
         work = new double[2 * nY * nZ];
       } else {
         work = null;
       }
     }
 
     @Override
     public void run(final int lb, final int ub) {
       if (localZTranspose) {
         for (int x = lb; x <= ub; x++) {
           int inputOffset = x * nextX;
           transpose(input, inputOffset, work, 0);
           localFFTZ.fft(work, 0, ii);
           unTranspose(input, inputOffset, work, 0);
         }
       } else {
         for (int x = lb; x <= ub; x++) {
           int offset = x * nY * nZ * ii;
           localFFTZ.fft(work3D, offset, ii);
         }
       }
     }
 
     @Override
     public IntegerSchedule schedule() {
       return schedule;
     }
 
     public long getTime() {
       return time;
     }
 
     @Override
     public void finish() {
       time += System.nanoTime();
     }
 
     @Override
     public void start() {
       time -= System.nanoTime();
       int threadID = getThreadIndex();
       localFFTZ = fftZ[threadID];
     }
   }
 
   private class IFFTZLoop extends IntegerForLoop {
 
     private Complex localFFTZ;
     private long time;
     private final double[] work;
 
     private IFFTZLoop() {
       if (localZTranspose) {
         work = new double[2 * nY * nZ];
       } else {
         work = null;
       }
     }
 
     @Override
     public void run(final int lb, final int ub) {
       if (localZTranspose) {
         for (int x = lb; x <= ub; x++) {
           int inputOffset = x * nextX;
           transpose(input, inputOffset, work, 0);
           localFFTZ.ifft(work, 0, ii);
           unTranspose(input, inputOffset, work, 0);
         }
       } else {
         for (int x = lb; x <= ub; x++) {
           int offset = x * nY * nZ * ii;
           localFFTZ.ifft(work3D, offset, ii);
         }
       }
     }
 
     @Override
     public IntegerSchedule schedule() {
       return schedule;
     }
 
     public long getTime() {
       return time;
     }
 
     @Override
     public void finish() {
       time += System.nanoTime();
     }
 
     @Override
     public void start() {
       time -= System.nanoTime();
       int threadID = getThreadIndex();
       localFFTZ = fftZ[threadID];
     }
   }
 
   private class FFTZIZLoop extends IntegerForLoop {
 
     private Complex localFFTZ;
     private long time;
     private final double[] work;
 
     private FFTZIZLoop() {
       if (localZTranspose) {
         work = new double[2 * nY * nZ];
       } else {
         work = null;
       }
     }
 
     @Override
     public void run(final int lb, final int ub) {
       if (localZTranspose) {
         for (int x = lb; x <= ub; x++) {
           int inputOffset = x * nextX;
           transpose(input, inputOffset, work, 0);
           localFFTZ.fft(work, 0, ii);
           int recipOffset = x * nY * nZ;
           recipConv(recipOffset, work, 0);
           localFFTZ.ifft(work, 0, ii);
           unTranspose(input, inputOffset, work, 0);
         }
       } else {
         for (int x = lb; x <= ub; x++) {
           // Offset into the work3D array.
           int offset = x * nY * nZ * ii;
           localFFTZ.fft(work3D, offset, ii);
           int recipOffset = x * nY * nZ;
           recipConv(recipOffset, work3D, offset);
           localFFTZ.ifft(work3D, offset, ii);
         }
       }
     }
 
     @Override
     public IntegerSchedule schedule() {
       return schedule;
     }
 
     public long getTime() {
       return time;
     }
 
     public void finish() {
       time += System.nanoTime();
     }
 
     @Override
     public void start() {
       time -= System.nanoTime();
       int threadID = getThreadIndex();
       localFFTZ = fftZ[threadID];
     }
   }
 
   /**
    * The input data order is X,Y,Z (X varies most quickly)
    * real[x, y, z] = input[x*nextX + y*nextY + z*nextZ]
    * imag[x, y, z] = input[x*nextX + y*nextY + z*nextZ + im]
    * The output data order is Y,Z,X (Y varies most quickly)
    * real[x, y, z] = input[y*trNextY + z*trNextZ + x*trNextX]
    * imag[x, y, z] = input[y*trNextY + z*trNextZ + x*trNextX + im]
    */
   private class TransposeLoop extends IntegerForLoop {
 
     private long time;
 
     @Override
     public void run(final int lb, final int ub) {
       for (int x = lb; x <= ub; x++) {
         for (int z = 0; z < nZ; z++) {
           int inputOffset = x * nextX + z * nextZ;
           int workOffset = x * trNextX + z * trNextZ;
           for (int y = 0; y < nY; y++) {
             int inputIndex = inputOffset + y * nextY;
             double real = input[inputIndex];
             double imag = input[inputIndex + im];
             int workIndex = workOffset + y * trNextY;
             work3D[workIndex] = real;
             work3D[workIndex + internalImZ] = imag;
           }
         }
       }
     }
 
     /**
      * Use a fixed schedule to minimize cache interference.
      *
      * @return A fixed IntegerSchedule.
      */
     @Override
     public IntegerSchedule schedule() {
       return IntegerSchedule.fixed();
     }
 
     public long getTime() {
       return time;
     }
 
     @Override
     public void finish() {
       time += System.nanoTime();
     }
 
     @Override
     public void start() {
       time -= System.nanoTime();
     }
   }
 
   /**
    * The transposed input data order is Y,Z,X (Y varies most quickly)
    * real[x, y, z] = input[y*trNextY + z*trNextZ + x*trNextX]
    * imag[x, y, z] = input[y*trNextY + z*trNextZ + x*trNextX + im]
    * <p>
    * The output data order is X,Y,Z (X varies most quickly)
    * real[x, y, z] = input[x*nextX + y*nextY + z*nextZ]
    * imag[x, y, z] = input[x*nextX + y*nextY + z*nextZ + im]
    */
   private class UnTransposeLoop extends IntegerForLoop {
 
     private long time;
 
     @Override
     public void run(final int lb, final int ub) {
       for (int x = 0; x < nX; x++) {
         for (int y = 0; y < nY; y++) {
           int workOffset = x * trNextX + y * trNextY;
           int inputOffset = x * nextX + y * nextY;
           for (int z = lb; z <= ub; z++) {
             int workIndex = workOffset + z * trNextZ;
             double real = work3D[workIndex];
             double imag = work3D[workIndex + internalImZ];
             int inputIndex = inputOffset + z * nextZ;
             input[inputIndex] = real;
             input[inputIndex + im] = imag;
           }
         }
       }
     }
 
     /**
      * Use a dynamic schedule to account mitigate latency reading from the work array.
      *
      * @return A dynamic IntegerSchedule.
      */
     @Override
     public IntegerSchedule schedule() {
       return IntegerSchedule.fixed();
     }
 
     public long getTime() {
       return time;
     }
 
     @Override
     public void finish() {
       time += System.nanoTime();
     }
 
     @Override
     public void start() {
       time -= System.nanoTime();
     }
   }
 
   /**
    * Perform a multiplication by the reciprocal space data.
    *
    * @param recipOffset The offset into the reciprocal space data (x * nY * nZ).
    * @param work        The input array.
    * @param workOffset  The offset into the data array (x * nY * nZ * ii).
    */
   private void recipConv(int recipOffset, double[] work, int workOffset) {
     if (useSIMD && internalImZ == 1) {
       // Only for interleaved data at the moment.
       recipConvSIMD(recipOffset, work, workOffset);
       // recipConvScalar(recipOffset, work, workOffset);
     } else {
       recipConvScalar(recipOffset, work, workOffset);
     }
   }
 
   /**
    * Scalar implementation of reciprocal space multiplication.
    *
    * @param recipOffset The offset into the reciprocal space data (x * nY * nZ).
    * @param work        The input array.
    * @param workOffset  The offset into the data array (x * nY * nZ * ii).
    */
   private void recipConvScalar(int recipOffset, double[] work, int workOffset) {
     int index = workOffset;
     int rindex = recipOffset;
     for (int i = 0; i < nY * nZ; i++) {
       double r = recip[rindex++];
       work[index] *= r;
       work[index + internalImZ] *= r;
       index += ii;
     }
   }
 
   /**
    * Preliminary SIMD implementation of reciprocal space multiplication.
    *
    * @param recipOffset The offset into the reciprocal space data (x * nY * nZ).
    * @param work        The input array.
    * @param workOffset  The offset into the data array (x * nY * nZ * ii).
    */
   private void recipConvSIMD(int recipOffset, double[] work, int workOffset) {
 
     // Check if the data is interleaved.
     if (internalImZ != 1) {
       logger.severe(" Real and imaginary parts must be interleaved.");
     }
 
     // Calculate the number of elements to process
     int length = nY * nZ * 2;
     // One load of from the reciprocal space data is used for two loads for the work array.
     int vectorSize2 = vectorSize * 2;
     int vectorizedLength = (length / vectorSize2) * vectorSize2;
 
     // Process elements in chunks of 2 * vectorSize.
     int i = 0;
     for (; i < vectorizedLength; i += vectorSize2) {
       // Load reciprocal space scalars for two chunks of complex numbers.
       DoubleVector recipVector = DoubleVector.fromArray(species, recip, recipOffset + i / 2);
 
       // Load the first chunk of complex numbers and perform the reciprocal multiplication
       DoubleVector complexVector = DoubleVector.fromArray(species, work, workOffset + i);
       DoubleVector firstHalf = recipVector.rearrange(expandFirstHalf);
       complexVector = complexVector.mul(firstHalf);
       complexVector.intoArray(work, workOffset + i);
 
       // Load the second chunk of complex numbers and perform the reciprocal multiplication
       complexVector = DoubleVector.fromArray(species, work, workOffset + vectorSize + i);
       DoubleVector secondHalf = recipVector.rearrange(expandSecondHalf);
       complexVector = complexVector.mul(secondHalf);
       complexVector.intoArray(work, workOffset + vectorSize + i);
     }
 
     // Process remaining elements
     for (; i < length; i+=2) {
       double r = recip[recipOffset + i / 2];
       work[workOffset + i] *= r;
       work[workOffset + i + internalImZ] *= r;
     }
   }
 
   /**
    * Load the Y-Z plane at fixed X into the work array.
    *
    * @param input        The input array.
    * @param inputOffset  The input offset (typically x * nextX).
    * @param output       The output array.
    * @param outputOffset The output offset (typically zero).
    */
   private void transpose(double[] input, int inputOffset, double[] output, int outputOffset) {
     // Typically the inputOffset is x * nextX.
     // Typically the outputOffset is 0.
     for (int z = 0; z < nZ; z++) {
       for (int y = 0; y < nY; y++) {
         double real = input[inputOffset + y * nextY + z * nextZ];
         double imag = input[inputOffset + y * nextY + z * nextZ + im];
         output[outputOffset + y * trNextY + z * trNextZ] = real;
         output[outputOffset + y * trNextY + z * trNextZ + internalImZ] = imag;
       }
     }
   }
 
   /**
    * Load the Y-Z plane at fixed X back into the input array.
    *
    * @param input        The input array.
    * @param inputOffset  The input offset (typically x * nextX).
    * @param output       The output array.
    * @param outputOffset The output offset (typically zero).
    */
   private void unTranspose(double[] input, int inputOffset, double[] output, int outputOffset) {
     // Typically the inputOffset is x * nextX.
     // Typically the outputOffset is 0.
     for (int z = 0; z < nZ; z++) {
       for (int y = 0; y < nY; y++) {
         double real = output[outputOffset + y * trNextY + z * trNextZ];
         double imag = output[outputOffset + y * trNextY + z * trNextZ + internalImZ];
         input[inputOffset + y * nextY + z * nextZ] = real;
         input[inputOffset + y * nextY + z * nextZ + im] = imag;
       }
     }
   }
 
   /**
    * Initialize a 3D data for testing purposes.
    *
    * @param dim          The dimension of the cube.
    * @param parallelTeam The parallel team.
    * @return The 3D data.
    * @since 1.0
    */
   public static double[] initRandomData(int dim, ParallelTeam parallelTeam) {
     int n = dim * dim * dim;
     double[] data = new double[2 * n];
     try {
       parallelTeam.execute(
           new ParallelRegion() {
             @Override
             public void run() {
               try {
                 execute(
                     0,
                     dim - 1,
                     new IntegerForLoop() {
                       @Override
                       public void run(final int lb, final int ub) {
                         Random randomNumberGenerator = new Random(1);
                         int index = dim * dim * lb * 2;
                         for (int i = lb; i <= ub; i++) {
                           for (int j = 0; j < dim; j++) {
                             for (int k = 0; k < dim; k++) {
                               double randomNumber = randomNumberGenerator.nextDouble();
                               data[index] = randomNumber;
                               index += 2;
                             }
                           }
                         }
                       }
                     });
               } catch (Exception e) {
                 System.out.println(e.getMessage());
                 System.exit(-1);
               }
             }
           });
     } catch (Exception e) {
       System.out.println(e.getMessage());
       System.exit(-1);
     }
     return data;
   }
 
   /**
    * Test the Complex3DParallel FFT.
    *
    * @param args an array of {@link java.lang.String} objects.
    * @throws java.lang.Exception if any.
    * @since 1.0
    */
   public static void main(String[] args) throws Exception {
     int dimNotFinal = 128;
     int nCPU = ParallelTeam.getDefaultThreadCount();
     int reps = 5;
     boolean blocked = false;
     try {
       dimNotFinal = Integer.parseInt(args[0]);
       if (dimNotFinal < 1) {
         dimNotFinal = 100;
       }
       nCPU = Integer.parseInt(args[1]);
       if (nCPU < 1) {
         nCPU = ParallelTeam.getDefaultThreadCount();
       }
       reps = Integer.parseInt(args[2]);
       if (reps < 1) {
         reps = 5;
       }
       blocked = Boolean.parseBoolean(args[3]);
     } catch (Exception e) {
       //
     }
     final int dim = dimNotFinal;
     System.out.printf("Initializing a %d cubed grid for %d CPUs.\n"
             + "The best timing out of %d repetitions will be used.%n",
         dim, nCPU, reps);
     // One dimension of the serial array divided by the number of threads.
     Complex3D complex3D;
     Complex3DParallel complex3DParallel;
     ParallelTeam parallelTeam = new ParallelTeam(nCPU);
     if (blocked) {
       complex3D = new Complex3D(dim, dim, dim, DataLayout3D.BLOCKED_X);
       complex3DParallel = new Complex3DParallel(dim, dim, dim, parallelTeam, DataLayout3D.BLOCKED_X);
     } else {
       complex3D = new Complex3D(dim, dim, dim, DataLayout3D.INTERLEAVED);
       complex3DParallel = new Complex3DParallel(dim, dim, dim, parallelTeam, DataLayout3D.INTERLEAVED);
     }
     final int dimCubed = dim * dim * dim;
     final double[] data = initRandomData(dim, parallelTeam);
     final double[] work = new double[dimCubed];
     Arrays.fill(work, 1.0);
 
     double toSeconds = 0.000000001;
     long seqTime = Long.MAX_VALUE;
     long parTime = Long.MAX_VALUE;
     long seqTimeConv = Long.MAX_VALUE;
     long parTimeConv = Long.MAX_VALUE;
 
     complex3D.setRecip(work);
     complex3DParallel.setRecip(work);
 
     // Warm-up
     System.out.println("Warm Up Sequential FFT");
     complex3D.fft(data);
     System.out.println("Warm Up Sequential IFFT");
     complex3D.ifft(data);
     System.out.println("Warm Up Sequential Convolution");
     complex3D.convolution(data);
 
 
 
     for (int i = 0; i < reps; i++) {
       System.out.printf(" Iteration %d%n", i + 1);
       long time = System.nanoTime();
       complex3D.fft(data);
       complex3D.ifft(data);
       time = (System.nanoTime() - time);
       System.out.printf("  Sequential FFT:  %9.6f (sec)%n", toSeconds * time);
       if (time < seqTime) {
         seqTime = time;
       }
       time = System.nanoTime();
       complex3D.convolution(data);
       time = (System.nanoTime() - time);
       System.out.printf("  Sequential Conv: %9.6f (sec)%n", toSeconds * time);
       if (time < seqTimeConv) {
         seqTimeConv = time;
       }
     }
 
     // Warm-up
     System.out.println("Warm up Parallel FFT");
     complex3DParallel.fft(data);
     System.out.println("Warm up Parallel IFFT");
     complex3DParallel.ifft(data);
     System.out.println("Warm up Parallel Convolution");
     complex3DParallel.convolution(data);
     complex3DParallel.initTiming();
 
     for (int i = 0; i < reps; i++) {
       // Reset timings after half the iterations.
       if (i == reps / 2) {
         complex3DParallel.initTiming();
       }
 
       System.out.printf(" Iteration %d%n", i + 1);
       long time = System.nanoTime();
       complex3DParallel.fft(data);
       complex3DParallel.ifft(data);
       time = (System.nanoTime() - time);
       System.out.printf("  Parallel FFT:  %9.6f (sec)%n", toSeconds * time);
       if (time < parTime) {
         parTime = time;
       }
 
       time = System.nanoTime();
       complex3DParallel.convolution(data);
       time = (System.nanoTime() - time);
       System.out.printf("  Parallel Conv: %9.6f (sec)%n", toSeconds * time);
       if (time < parTimeConv) {
         parTimeConv = time;
       }
 
     }
 
     System.out.printf(" Best Sequential FFT Time:   %9.6f (sec)%n", toSeconds * seqTime);
     System.out.printf(" Best Sequential Conv. Time: %9.6f (sec)%n", toSeconds * seqTimeConv);
     System.out.printf(" Best Parallel FFT Time:     %9.6f (sec)%n", toSeconds * parTime);
     System.out.printf(" Best Parallel Conv. Time:   %9.6f (sec)%n", toSeconds * parTimeConv);
     System.out.printf(" 3D FFT Speedup:             %9.6f X%n", (double) seqTime / parTime);
     System.out.printf(" 3D Conv Speedup:            %9.6f X%n", (double) seqTimeConv / parTimeConv);
 
     System.out.printf(" Parallel Convolution Timings:\n" + complex3DParallel.timingString());
 
     parallelTeam.shutdown();
   }
 }