Stan Math Library  2.10.0
reverse mode automatic differentiation
sqrt.hpp
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1 #ifndef STAN_MATH_REV_SCAL_FUN_SQRT_HPP
2 #define STAN_MATH_REV_SCAL_FUN_SQRT_HPP
3 
4 #include <stan/math/rev/core.hpp>
5 #include <cmath>
6 
7 namespace stan {
8  namespace math {
9 
10  namespace {
11  class sqrt_vari : public op_v_vari {
12  public:
13  explicit sqrt_vari(vari* avi) :
14  op_v_vari(std::sqrt(avi->val_), avi) {
15  }
16  void chain() {
17  avi_->adj_ += adj_ / (2.0 * val_);
18  }
19  };
20  }
21 
50  inline var sqrt(const var& a) {
51  return var(new sqrt_vari(a.vi_));
52  }
53 
54  }
55 }
56 #endif
fvar< T > sqrt(const fvar< T > &x)
Definition: sqrt.hpp:15
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

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