Stan Math Library  2.9.0
reverse mode automatic differentiation
log1p_exp.hpp
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1 #ifndef STAN_MATH_PRIM_SCAL_FUN_LOG1P_EXP_HPP
2 #define STAN_MATH_PRIM_SCAL_FUN_LOG1P_EXP_HPP
3 
4 #include <boost/math/tools/promotion.hpp>
6 
7 namespace stan {
8  namespace math {
9 
42  template <typename T>
43  inline typename boost::math::tools::promote_args<T>::type
44  log1p_exp(const T a) {
45  using std::exp;
46  // like log_sum_exp below with b=0.0; prevents underflow
47  if (a > 0.0)
48  return a + log1p(exp(-a));
49  return log1p(exp(a));
50  }
51 
52  }
53 }
54 
55 #endif
fvar< T > exp(const fvar< T > &x)
Definition: exp.hpp:10
fvar< T > log1p_exp(const fvar< T > &x)
Definition: log1p_exp.hpp:13
fvar< T > log1p(const fvar< T > &x)
Definition: log1p.hpp:16

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