Stan Math Library  2.9.0
reverse mode automatic differentiation
digamma.hpp
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1 #ifndef STAN_MATH_REV_SCAL_FUN_DIGAMMA_HPP
2 #define STAN_MATH_REV_SCAL_FUN_DIGAMMA_HPP
3 
4 #include <boost/math/special_functions/zeta.hpp>
5 #include <stan/math/rev/core.hpp>
8 
9 namespace stan {
10  namespace math {
11 
12  namespace {
13  class digamma_vari : public op_v_vari {
14  public:
15  explicit digamma_vari(vari* avi) :
16  op_v_vari(digamma(avi->val_), avi) {
17  }
18  void chain() {
19  avi_->adj_ += adj_ * trigamma(avi_->val_);
20  }
21  };
22  }
23 
24  inline var digamma(const stan::math::var& a) {
25  return var(new digamma_vari(a.vi_));
26  }
27 
28  }
29 }
30 #endif
T trigamma(T x)
Definition: trigamma.hpp:50
Independent (input) and dependent (output) variables for gradients.
Definition: var.hpp:31
vari * vi_
Pointer to the implementation of this variable.
Definition: var.hpp:43
fvar< T > digamma(const fvar< T > &x)
Definition: digamma.hpp:16

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