sparse_example.cpp

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// @HEADER
// *****************************************************************************
//                           Sacado Package
//
// Copyright 2006 NTESS and the Sacado contributors.
// SPDX-License-Identifier: LGPL-2.1-or-later
// *****************************************************************************
// @HEADER

// dfad_example
//
//  usage: 
//     dfad_example
//
//  output:  
//     prints the results of differentiating a simple function with forward
//     mode AD using the Sacado::Fad::DFad class (uses dynamic memory
//     allocation for number of derivative components).

#include <iostream>
#include <iomanip>

#include "Sacado_No_Kokkos.hpp"

// The function to differentiate
template <typename ScalarT>
ScalarT func(const ScalarT& a, const ScalarT& b, const ScalarT& c) {
  ScalarT r = std::log(b+1.)/std::sin(a);

  return r;
}

typedef Sacado::LFad::LogicalSparse<double,bool> FadType;

int main(int argc, char **argv)
{
  double pi = std::atan(1.0)*4.0;

  // Values of function arguments
  double a = pi/4;
  double b = 2.0;
  double c = 3.0;

  // Number of independent variables
  int num_deriv = 3;

  // Fad objects
  FadType afad(num_deriv, 0, a); // First (0) indep. var
  FadType bfad(num_deriv, 1, b); // Second (1) indep. var
  FadType cfad(num_deriv, 2, c); // Third (2) indep. var
  FadType rfad;                  // Result

  // Compute function
  double r = func(a, b, c);

  // Compute function and derivative with AD
  rfad = func(afad, bfad, cfad);

  std::cout << rfad << std::endl;

  // Extract value and derivatives
  double r_ad = rfad.val();     // r
  bool drda_ad = rfad.dx(0);  // dr/da
  bool drdb_ad = rfad.dx(1);  // dr/db
  bool drdc_ad = rfad.dx(2);  // dr/dc

  double tol = 1.0e-14;
  if (std::fabs(r - r_ad) < tol && drda_ad && drdb_ad && !drdc_ad) {
    std::cout << "\nExample passed!" << std::endl;
    return 0;
  }
  else {
    std::cout <<"\nSomething is wrong, example failed!" << std::endl;
    return 1;
  }
}