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log_diff_exp.hpp
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1 #ifndef STAN_MATH_FWD_SCAL_FUN_LOG_DIFF_EXP_HPP
2 #define STAN_MATH_FWD_SCAL_FUN_LOG_DIFF_EXP_HPP
3
4 #include <stan/math/fwd/core.hpp>
5
6 #include <stan/math/prim/scal/fun/log_diff_exp.hpp>
7 #include <stan/math/prim/scal/fun/constants.hpp>
8
9 namespace stan {
10 namespace math {
11
12 template <typename T> inline fvar<T>
13 log_diff_exp(const fvar<T>& x1, const fvar<T>& x2) {
14 using std::exp;
15 if (x1.val_ <= x2.val_)
16 return fvar<T>(NOT_A_NUMBER, NOT_A_NUMBER);
17 return fvar<T>(log_diff_exp(x1.val_, x2.val_),
18 x1.d_ / (1 - exp(x2.val_ - x1.val_))
19 + x2.d_ / (1 - exp(x1.val_ - x2.val_)));
20 }
21
22 template <typename T1, typename T2> inline fvar<T2>
23 log_diff_exp(const T1& x1, const fvar<T2>& x2) {
24 using std::exp;
25 if (x1 <= x2.val_)
26 return fvar<T2>(NOT_A_NUMBER, NOT_A_NUMBER);
27 return fvar<T2>(log_diff_exp(x1, x2.val_),
28 x2.d_ / (1 - exp(x1 - x2.val_)));
29 }
30
31 template <typename T1, typename T2> inline fvar<T1>
32 log_diff_exp(const fvar<T1>& x1, const T2& x2) {
33 using std::exp;
34 if (x1.val_ <= x2)
35 return fvar<T1>(NOT_A_NUMBER, NOT_A_NUMBER);
36 return fvar<T1>(log_diff_exp(x1.val_, x2),
37 x1.d_ / (1 - exp(x2 - x1.val_)));
38 }
39 }
40 }
41 #endif
log_diff_exp.hpp
core.hpp
stan::math::fvar::d_
T d_
Definition: fvar.hpp:14
stan::math::NOT_A_NUMBER
const double NOT_A_NUMBER
(Quiet) not-a-number value.
Definition: constants.hpp:55
stan
Definition: log_sum_exp.hpp:8
stan::math::log_diff_exp
fvar< T > log_diff_exp(const fvar< T > &x1, const fvar< T > &x2)
Definition: log_diff_exp.hpp:13
stan::math::fvar::val_
T val_
Definition: fvar.hpp:13
stan::math::exp
fvar< T > exp(const fvar< T > &x)
Definition: exp.hpp:10
constants.hpp
stan::math::fvar
Definition: fvar.hpp:12

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