/*
    * Licensed to the Hipparchus project under one or more
    * contributor license agreements.  See the NOTICE file distributed with
    * this work for additional information regarding copyright ownership.
    * The Hipparchus project licenses this file to You under the Apache License, Version 2.0
    * (the "License"); you may not use this file except in compliance with
    * the License.  You may obtain a copy of the License at
    *
    *      https://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  package org.hipparchus.optim.nonlinear.vector.constrained;
  
  import org.hipparchus.linear.Array2DRowRealMatrix;
  import org.hipparchus.linear.ArrayRealVector;
  import org.hipparchus.linear.RealMatrix;
  import org.hipparchus.linear.RealVector;
  
  public class HockSchittkowskiFunction71 extends TwiceDifferentiableFunction {
  
      @Override
      public int dim() {
          return 4;
      }
  
      @Override
      public double value(RealVector x) {
          double x1 = x.getEntry(0);
          double x2 = x.getEntry(1);
          double x3 = x.getEntry(2);
          double x4 = x.getEntry(3);
  
          return x1*x4*(x1+x2+x3)+x3;
      }
  
      @Override
      public RealVector gradient(RealVector x) {
          RealVector grad=new ArrayRealVector(x.getDimension());
          double x1 = x.getEntry(0);
          double x2 = x.getEntry(1);
          double x3 = x.getEntry(2);
          double x4 = x.getEntry(3);
          grad.setEntry(0,x4*(2.0*x1+x2+x3));
          grad.setEntry(1,x1*x4);
          grad.setEntry(2,x1*x4+1.0);
           grad.setEntry(3,x1*(x1+x2+x3));
          return grad;
      }
  
      @Override
      public RealMatrix hessian(RealVector x) {
          double x1 = x.getEntry(0);
          double x2 = x.getEntry(1);
          double x3 = x.getEntry(2);
          double x4 = x.getEntry(3);
          RealMatrix h=new Array2DRowRealMatrix(x.getDimension(),x.getDimension());
          h.setEntry(0,0, 2.0*x4);
          h.setEntry(0,1,x4);
          h.setEntry(0,2,x4);
          h.setEntry(0,3, (2*x1+x2+x3));
  
          h.setEntry(1,0, x4);
          h.setEntry(1,1, 0);
          h.setEntry(1,2, 0);
          h.setEntry(1,3, 0);
  
          h.setEntry(2,0, x4);
          h.setEntry(2,1, 0);
          h.setEntry(2,2, 0);
          h.setEntry(2,3, x1);
  
           h.setEntry(3,0, x1+x2+x3);
          h.setEntry(3,1, x1);
          h.setEntry(3,2, x1);
          h.setEntry(3,3, 0);
  
  
  
          return h;
      }
  
  }