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log_sum_exp.hpp
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1 #ifndef STAN_MATH_PRIM_MAT_FUN_LOG_SUM_EXP_HPP
2 #define STAN_MATH_PRIM_MAT_FUN_LOG_SUM_EXP_HPP
3
4 #include <stan/math/prim/scal/fun/log1p.hpp>
5 #include <stan/math/prim/mat/fun/Eigen.hpp>
6 #include <boost/math/tools/promotion.hpp>
7 #include <limits>
8 #include <vector>
9
10 namespace stan {
11
12 namespace math {
13
27 template <int R, int C>
28 double log_sum_exp(const Eigen::Matrix<double, R, C>& x) {
29 using std::numeric_limits;
30 using std::log;
31 using std::exp;
32 double max = -numeric_limits<double>::infinity();
33 for (int i = 0; i < x.size(); i++)
34 if (x(i) > max)
35 max = x(i);
36
37 double sum = 0.0;
38 for (int i = 0; i < x.size(); i++)
39 if (x(i) != -numeric_limits<double>::infinity())
40 sum += exp(x(i) - max);
41
42 return max + log(sum);
43 }
44
45 }
46 }
47
48 #endif
stan::math::sum
fvar< T > sum(const std::vector< fvar< T > > &m)
Return the sum of the entries of the specified standard vector.
Definition: sum.hpp:20
stan::math::log
fvar< T > log(const fvar< T > &x)
Definition: log.hpp:15
stan::math::log_sum_exp
fvar< T > log_sum_exp(const std::vector< fvar< T > > &v)
Definition: log_sum_exp.hpp:14
stan::math::exp
fvar< T > exp(const fvar< T > &x)
Definition: exp.hpp:10
Eigen.hpp
stan::math::max
int max(const std::vector< int > &x)
Returns the maximum coefficient in the specified column vector.
Definition: max.hpp:21
log1p.hpp

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