//******************************************************************************
   //
   // 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.
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  // Force Field X; if not, write to the Free Software Foundation, Inc., 59 Temple
  // Place, Suite 330, Boston, MA 02111-1307 USA
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  // combined work based on this library. Thus, the terms and conditions of the
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  package ffx.realspace.commands.test;
  
  import ffx.algorithms.cli.AlgorithmsCommand;
  import ffx.numerics.Potential;
  import ffx.potential.MolecularAssembly;
  import ffx.potential.bonded.LambdaInterface;
  import ffx.potential.cli.AlchemicalOptions;
  import ffx.potential.cli.GradientOptions;
  import ffx.realspace.RealSpaceData;
  import ffx.realspace.cli.RealSpaceOptions;
  import ffx.realspace.parsers.RealSpaceFile;
  import ffx.utilities.FFXBinding;
  import ffx.xray.RefinementEnergy;
  import picocli.CommandLine.Command;
  import picocli.CommandLine.Mixin;
  import picocli.CommandLine.Parameters;
  
  import java.util.ArrayList;
  import java.util.Collections;
  import java.util.List;
  import java.util.stream.IntStream;
  
  import static ffx.utilities.StringUtils.parseAtomRanges;
  
  /**
   * The Real Space Annealing script.
   * <br>
   * Usage:
   * <br>
   * ffxc realspace.test.LambdaGradient [options] &lt;filename&gt;
   */
  @Command(description = " Test Lambda Derivatives on a Real Space target.", name = "realspace.test.LambdaGradient")
  public class LambdaGradient extends AlgorithmsCommand {
  
    @Mixin
    private RealSpaceOptions realSpaceOptions;
  
    @Mixin
    private AlchemicalOptions alchemicalOptions;
  
    @Mixin
    private GradientOptions gradientOptions;
  
    /**
     * One or more filenames.
     */
    @Parameters(arity = "1..*", paramLabel = "files", description = "PDB and Real Space input files.")
    private List<String> filenames;
    
    private Potential potential;
  
    /**
     * LambdaGradient constructor.
     */
    public LambdaGradient() {
      super();
    }
  
    /**
     * LambdaGradient constructor that sets the command line arguments.
     * @param args Command line arguments.
     */
   public LambdaGradient(String[] args) {
     super(args);
   }
 
   /**
    * LambdaGradient constructor.
    * @param binding The Binding to use.
    */
   public LambdaGradient(FFXBinding binding) {
     super(binding);
   }
 
   @Override
   public LambdaGradient run() {
 
     if (!init()) {
       return this;
     }
 
     // Turn on computation of lambda derivatives
     System.setProperty("lambdaterm", "true");
 
     String modelfilename;
     MolecularAssembly[] assemblies;
     if (filenames != null && filenames.size() > 0) {
       assemblies = algorithmFunctions.openAll(filenames.get(0));
       activeAssembly = assemblies[0];
       modelfilename = filenames.get(0);
     } else if (activeAssembly == null) {
       logger.info(helpString());
       return this;
     } else {
       modelfilename = activeAssembly.getFile().getAbsolutePath();
       assemblies = new MolecularAssembly[]{activeAssembly};
     }
 
     alchemicalOptions.setFirstSystemAlchemistry(activeAssembly);
     alchemicalOptions.setFirstSystemUnchargedAtoms(activeAssembly);
 
     logger.info("\n Testing lambda derivatives for " + modelfilename);
 
     List<RealSpaceFile> mapfiles = realSpaceOptions.processData(filenames, activeAssembly);
     RealSpaceFile[] mapFileArray = mapfiles.toArray(new RealSpaceFile[0]);
 
     RealSpaceData realspacedata = new RealSpaceData(activeAssembly, activeAssembly.getProperties(),
         activeAssembly.getParallelTeam(), mapFileArray);
 
     RefinementEnergy refinementEnergy = new RefinementEnergy(realspacedata,
         realSpaceOptions.refinementMode);
     potential = refinementEnergy;
     LambdaInterface lambdaInterface = refinementEnergy;
 
     // Reset the number of variables for the case of dual topology.
     int n = potential.getNumberOfVariables();
     double[] x = new double[n];
     double[] gradient = new double[n];
     double[] lambdaGrad = new double[n];
     double[][] lambdaGradFD = new double[2][n];
 
     // Number of independent atoms.
     assert (n % 3 == 0);
     int nAtoms = n / 3;
 
     // Compute the Lambda = 0.0 energy.
     double lambda = 0.0;
     lambdaInterface.setLambda(lambda);
     potential.getCoordinates(x);
     double e0 = potential.energy(x, true);
 
     // Compute the Lambda = 1.0 energy.
     lambda = 1.0;
     lambdaInterface.setLambda(lambda);
     double e1 = potential.energy(x, true);
 
     logger.info(String.format(" E(0):      %20.8f.", e0));
     logger.info(String.format(" E(1):      %20.8f.", e1));
     logger.info(String.format(" E(1)-E(0): %20.8f.\n", e1 - e0));
 
     // Finite-difference step size.
     double step = gradientOptions.getDx();
     double width = 2.0 * step;
 
     // Error tolerence
     double errTol = 1.0e-3;
     // Upper bound for typical gradient sizes (expected gradient)
     double expGrad = 1000.0;
 
     double initialLambda = alchemicalOptions.getInitialLambda();
 
     // Test Lambda gradient in the neighborhood of the lambda variable.
     for (int j = 0; j < 3; j++) {
       lambda = initialLambda - 0.01 + 0.01 * j;
 
       if (lambda - step < 0.0) {
         continue;
       }
       if (lambda + step > 1.0) {
         continue;
       }
 
       logger.info(String.format(" Current lambda value %6.4f", lambda));
       lambdaInterface.setLambda(lambda);
 
       // Calculate the energy, dE/dX, dE/dL, d2E/dL2 and dE/dL/dX
       double e = potential.energyAndGradient(x, gradient);
 
       // Analytic dEdL, d2E/dL2 and dE/dL/dX
       double dEdL = lambdaInterface.getdEdL();
       double d2EdL2 = lambdaInterface.getd2EdL2();
       for (int i = 0; i < n; i++) {
         lambdaGrad[i] = 0.0;
       }
 
       lambdaInterface.getdEdXdL(lambdaGrad);
 
       // Calculate the finite-difference dEdLambda, d2EdLambda2 and dEdLambdadX
       lambdaInterface.setLambda(lambda + step);
       double lp = potential.energyAndGradient(x, lambdaGradFD[0]);
       double dedlp = lambdaInterface.getdEdL();
       lambdaInterface.setLambda(lambda - step);
       double lm = potential.energyAndGradient(x, lambdaGradFD[1]);
       double dedlm = lambdaInterface.getdEdL();
 
       double dEdLFD = (lp - lm) / width;
       double d2EdL2FD = (dedlp - dedlm) / width;
 
       double err = Math.abs(dEdLFD - dEdL);
       if (err < errTol) {
         logger.info(String.format(" dE/dL passed:   %10.6f", err));
       } else {
         logger.info(String.format(" dE/dL failed: %10.6f", err));
       }
       logger.info(String.format(" Numeric:   %15.8f", dEdLFD));
       logger.info(String.format(" Analytic:  %15.8f", dEdL));
 
       err = Math.abs(d2EdL2FD - d2EdL2);
       if (err < errTol) {
         logger.info(String.format(" d2E/dL2 passed: %10.6f", err));
       } else {
         logger.info(String.format(" d2E/dL2 failed: %10.6f", err));
       }
       logger.info(String.format(" Numeric:   %15.8f", d2EdL2FD));
       logger.info(String.format(" Analytic:  %15.8f", d2EdL2));
 
       boolean passed = true;
 
       for (int i = 0; i < nAtoms; i++) {
         int ii = i * 3;
         double dX = (lambdaGradFD[0][ii] - lambdaGradFD[1][ii]) / width;
         double dXa = lambdaGrad[ii];
         double eX = dX - dXa;
         ii++;
         double dY = (lambdaGradFD[0][ii] - lambdaGradFD[1][ii]) / width;
         double dYa = lambdaGrad[ii];
         double eY = dY - dYa;
         ii++;
         double dZ = (lambdaGradFD[0][ii] - lambdaGradFD[1][ii]) / width;
         double dZa = lambdaGrad[ii];
         double eZ = dZ - dZa;
 
         double error = Math.sqrt(eX * eX + eY * eY + eZ * eZ);
         if (error < errTol) {
           logger.fine(String.format(" dE/dX/dL for Atom %d passed: %10.6f", i + 1, error));
         } else {
           logger.info(String.format(" dE/dX/dL for Atom %d failed: %10.6f", i + 1, error));
           logger.info(String.format(" Analytic: (%15.8f, %15.8f, %15.8f)", dXa, dYa, dZa));
           logger.info(String.format(" Numeric:  (%15.8f, %15.8f, %15.8f)", dX, dY, dZ));
           passed = false;
         }
       }
       if (passed) {
         logger.info(String.format(" dE/dX/dL passed for all atoms"));
       }
 
       logger.info("");
     }
 
     boolean loopPrint = gradientOptions.getVerbose();
     lambdaInterface.setLambda(initialLambda);
     potential.getCoordinates(x);
     potential.energyAndGradient(x, gradient, loopPrint);
 
     logger.info(String.format(" Checking Cartesian coordinate gradient"));
 
     double[] numeric = new double[3];
     double avLen = 0.0;
     int nFailures = 0;
     double avGrad = 0.0;
 
 
     // Collect atoms to test.
     List<Integer> atomsToTest;
     if (gradientOptions.getGradientAtoms().equalsIgnoreCase("NONE")) {
       logger.info(" The gradient of no atoms will be evaluated.");
       return this;
     } else if (gradientOptions.getGradientAtoms().equalsIgnoreCase("ALL")) {
       logger.info(" Checking gradient for all active atoms.\n");
       atomsToTest = new ArrayList<>();
       IntStream.range(0, nAtoms).forEach(val -> atomsToTest.add(val));
     } else {
       atomsToTest = parseAtomRanges(" Gradient atoms", gradientOptions.getGradientAtoms(), nAtoms);
       logger.info(
           " Checking gradient for active atoms in the range: " + gradientOptions.getGradientAtoms() + "\n");
     }
 
     for (int i : atomsToTest) {
       int i3 = i * 3;
       int i0 = i3 + 0;
       int i1 = i3 + 1;
       int i2 = i3 + 2;
 
       // Find numeric dX
       double orig = x[i0];
       x[i0] = x[i0] + step;
       double e = potential.energyAndGradient(x, lambdaGradFD[0], loopPrint);
       x[i0] = orig - step;
       e -= potential.energyAndGradient(x, lambdaGradFD[1], loopPrint);
       x[i0] = orig;
       numeric[0] = e / width;
 
       // Find numeric dY
       orig = x[i1];
       x[i1] = x[i1] + step;
       e = potential.energyAndGradient(x, lambdaGradFD[0], loopPrint);
       x[i1] = orig - step;
       e -= potential.energyAndGradient(x, lambdaGradFD[1], loopPrint);
       x[i1] = orig;
       numeric[1] = e / width;
 
       // Find numeric dZ
       orig = x[i2];
       x[i2] = x[i2] + step;
       e = potential.energyAndGradient(x, lambdaGradFD[0], loopPrint);
       x[i2] = orig - step;
       e -= potential.energyAndGradient(x, lambdaGradFD[1], loopPrint);
       x[i2] = orig;
       numeric[2] = e / width;
 
       double dx = gradient[i0] - numeric[0];
       double dy = gradient[i1] - numeric[1];
       double dz = gradient[i2] - numeric[2];
       double len = dx * dx + dy * dy + dz * dz;
       avLen += len;
       len = Math.sqrt(len);
 
       double grad2 =
           gradient[i0] * gradient[i0] + gradient[i1] * gradient[i1] + gradient[i2] * gradient[i2];
       avGrad += grad2;
       grad2 = Math.sqrt(grad2);
 
       if (len > errTol) {
         logger.info(String.format(" Atom %d failed: %10.6f.", i + 1, len)
             + String.format("\n Analytic: (%12.4f, %12.4f, %12.4f)\n", gradient[i0], gradient[i1],
             gradient[i2])
             + String.format(" Numeric:  (%12.4f, %12.4f, %12.4f)\n", numeric[0], numeric[1],
             numeric[2]));
         ++nFailures;
         //return this;
       } else {
         logger.info(String.format(" Atom %d passed: %10.6f.", i + 1, len)
             + String.format("\n Analytic: (%12.4f, %12.4f, %12.4f)\n", gradient[i0], gradient[i1],
             gradient[i2])
             + String.format(" Numeric:  (%12.4f, %12.4f, %12.4f)", numeric[0], numeric[1],
             numeric[2]));
       }
 
       if (grad2 > expGrad) {
         logger.info(String.format(" Atom %d has an unusually large gradient: %10.6f", i + 1, grad2));
       }
       logger.info("\n");
     }
 
     avLen = avLen / nAtoms;
     avLen = Math.sqrt(avLen);
     if (avLen > errTol) {
       logger.info(String.
           format(" Test failure: RMSD from analytic solution is %10.6f > %10.6f", avLen, errTol));
     } else {
       logger.info(String.
           format(" Test success: RMSD from analytic solution is %10.6f < %10.6f", avLen, errTol));
     }
     logger.info(String.format(" Number of atoms failing gradient test: %d", nFailures));
 
     avGrad = avGrad / nAtoms;
     avGrad = Math.sqrt(avGrad);
     if (avGrad > expGrad) {
       logger.info(String.format(" Unusually large RMS gradient: %10.6f > %10.6f", avGrad, expGrad));
     } else {
       logger.info(String.format(" RMS gradient: %10.6f", avGrad));
     }
 
     return this;
   }
 
   @Override
   public List<Potential> getPotentials() {
     return potential == null ? Collections.emptyList() : Collections.singletonList(potential);
   }
 }