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trad_example.cpp
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31 
32 // trad_example
33 //
34 // usage:
35 // trad_example
36 //
37 // output:
38 // prints the results of differentiating a simple function with reverse
39 // mode AD using the Sacado::Rad::ADvar class.
40 
41 #include <iostream>
42 #include <iomanip>
43 
44 #include "Sacado_No_Kokkos.hpp"
45 
46 // The function to differentiate
47 template <typename ScalarT>
48 ScalarT func(const ScalarT& a, const ScalarT& b, const ScalarT& c) {
49  ScalarT r = c*std::log(b+1.)/std::sin(a);
50 
51  return r;
52 }
53 
54 // The analytic derivative of func(a,b,c) with respect to a and b
55 void func_deriv(double a, double b, double c, double& drda, double& drdb)
56 {
57  drda = -(c*std::log(b+1.)/std::pow(std::sin(a),2.))*std::cos(a);
58  drdb = c / ((b+1.)*std::sin(a));
59 }
60 
61 int main(int argc, char **argv)
62 {
63  double pi = std::atan(1.0)*4.0;
64 
65  // Values of function arguments
66  double a = pi/4;
67  double b = 2.0;
68  double c = 3.0;
69 
70  // Rad objects
73  Sacado::Rad::ADvar<double> crad = c; // Passive variable
74  Sacado::Rad::ADvar<double> rrad; // Result
75 
76  // Compute function
77  double r = func(a, b, c);
78 
79  // Compute derivative analytically
80  double drda, drdb;
81  func_deriv(a, b, c, drda, drdb);
82 
83  // Compute function and derivative with AD
84  rrad = func(arad, brad, crad);
85 
87 
88  // Extract value and derivatives
89  double r_ad = rrad.val(); // r
90  double drda_ad = arad.adj(); // dr/da
91  double drdb_ad = brad.adj(); // dr/db
92 
93  // Print the results
94  int p = 4;
95  int w = p+7;
96  std::cout.setf(std::ios::scientific);
97  std::cout.precision(p);
98  std::cout << " r = " << r << " (original) == " << std::setw(w) << r_ad
99  << " (AD) Error = " << std::setw(w) << r - r_ad << std::endl
100  << "dr/da = " << std::setw(w) << drda << " (analytic) == "
101  << std::setw(w) << drda_ad << " (AD) Error = " << std::setw(w)
102  << drda - drda_ad << std::endl
103  << "dr/db = " << std::setw(w) << drdb << " (analytic) == "
104  << std::setw(w) << drdb_ad << " (AD) Error = " << std::setw(w)
105  << drdb - drdb_ad << std::endl;
106 
107  double tol = 1.0e-14;
108 
109  if (std::fabs(r - r_ad) < tol &&
110  std::fabs(drda - drda_ad) < tol &&
111  std::fabs(drdb - drdb_ad) < tol) {
112  std::cout << "\nExample passed!" << std::endl;
113  return 0;
114  }
115  else {
116  std::cout <<"\nSomething is wrong, example failed!" << std::endl;
117  return 1;
118  }
119 }
static void Gradcomp()
atan(expr.val())
KOKKOS_INLINE_FUNCTION mpl::enable_if_c< ExprLevel< Expr< T1 > >::value==ExprLevel< Expr< T2 > >::value, Expr< PowerOp< Expr< T1 >, Expr< T2 > > > >::type pow(const Expr< T1 > &expr1, const Expr< T2 > &expr2)
expr expr1 expr1 expr1 c expr2 expr1 expr2 expr1 expr2 expr1 expr1 expr1 expr1 c expr2 expr1 expr2 expr1 expr2 expr1 expr1 expr1 expr1 c *expr2 expr1 expr2 expr1 expr2 expr1 expr1 expr1 expr1 c expr2 expr1 expr2 expr1 expr2 expr1 expr1 expr1 expr2 expr1 expr2 expr1 expr1 expr1 expr2 expr1 expr2 expr1 expr1 expr1 c
int main()
Definition: ad_example.cpp:191
void func_deriv(double a, double b, double c, double &drda, double &drdb)
sin(expr.val())
log(expr.val())
const double tol
const T func(int n, T *x)
Definition: ad_example.cpp:49
fabs(expr.val())
cos(expr.val())