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finite_diff_gradient.hpp
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1 #ifndef STAN_MATH_PRIM_MAT_FUNCTOR_FINITE_DIFF_GRADIENT_HPP
2 #define STAN_MATH_PRIM_MAT_FUNCTOR_FINITE_DIFF_GRADIENT_HPP
3
4 #include <stan/math/prim/mat/fun/Eigen.hpp>
5
6 namespace stan {
7
8 namespace math {
9
37 template <typename F>
38 void
39 finite_diff_gradient(const F& f,
40 const Eigen::Matrix<double, -1, 1>& x,
41 double& fx,
42 Eigen::Matrix<double, -1, 1>& grad_fx,
43 const double epsilon = 1e-03) {
44 using Eigen::Matrix;
45 using Eigen::Dynamic;
46 Matrix<double, Dynamic, 1> x_temp(x);
47
48 int d = x.size();
49 grad_fx.resize(d);
50
51 fx = f(x);
52
53 for (int i = 0; i < d; ++i) {
54 double delta_f = 0.0;
55
56 x_temp(i) = x(i) + 3.0 * epsilon;
57 delta_f = f(x_temp);
58
59 x_temp(i) = x(i) + 2.0 * epsilon;
60 delta_f -= 9.0 * f(x_temp);
61
62 x_temp(i) = x(i) + epsilon;
63 delta_f += 45.0 * f(x_temp);
64
65 x_temp(i) = x(i) + -3.0 * epsilon;
66 delta_f -= f(x_temp);
67
68 x_temp(i) = x(i) + -2.0 * epsilon;
69 delta_f += 9.0 * f(x_temp);
70
71 x_temp(i) = x(i) + -epsilon;
72 delta_f -= 45.0 * f(x_temp);
73
74 delta_f /= 60 * epsilon;
75
76 x_temp(i) = x(i);
77 grad_fx(i) = delta_f;
78 }
79 }
80 }
81 }
82 #endif
Eigen.hpp
stan::math::e
double e()
Return the base of the natural logarithm.
Definition: constants.hpp:95
stan::math::finite_diff_gradient
void finite_diff_gradient(const F &f, const Eigen::Matrix< double,-1, 1 > &x, double &fx, Eigen::Matrix< double,-1, 1 > &grad_fx, const double epsilon=1e-03)
Calculate the value and the gradient of the specified function at the specified argument using finite...
Definition: finite_diff_gradient.hpp:39

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