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precomputed_gradients.hpp
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1 #ifndef STAN_MATH_REV_CORE_PRECOMPUTED_GRADIENTS_HPP
2 #define STAN_MATH_REV_CORE_PRECOMPUTED_GRADIENTS_HPP
3
4 #include <stan/math/rev/core/vari.hpp>
5 #include <stan/math/rev/core/var.hpp>
6 #include <algorithm>
7 #include <stdexcept>
8 #include <vector>
9
10 namespace stan {
11
12 namespace math {
13
21 class precomputed_gradients_vari : public vari {
22 protected:
23 const size_t size_;
24 vari** varis_;
25 double* gradients_;
26
27 public:
37 precomputed_gradients_vari(double val,
38 size_t size,
39 vari** varis,
40 double* gradients)
41 : vari(val),
42 size_(size),
43 varis_(varis),
44 gradients_(gradients) {
45 }
46
58 precomputed_gradients_vari(double val,
59 const std::vector<var>& vars,
60 const std::vector<double>& gradients)
61 : vari(val),
62 size_(vars.size()),
63 varis_(ChainableStack::memalloc_
64 .alloc_array<vari*>(vars.size())),
65 gradients_(ChainableStack::memalloc_
66 .alloc_array<double>(vars.size())) {
67 if (vars.size() != gradients.size())
68 throw std::invalid_argument("sizes of vars and gradients"
69 " do not match");
70 for (size_t i = 0; i < vars.size(); ++i)
71 varis_[i] = vars[i].vi_;
72 std::copy(gradients.begin(), gradients.end(), gradients_);
73 }
74
79 void chain() {
80 for (size_t i = 0; i < size_; ++i)
81 varis_[i]->adj_ += adj_ * gradients_[i];
82 }
83 };
84
85
98 inline var precomputed_gradients(const double value,
99 const std::vector<var>& operands,
100 const std::vector<double>& gradients) {
101 return var(new precomputed_gradients_vari(value, operands, gradients));
102 }
103 }
104 }
105 #endif
stan::math::precomputed_gradients
var precomputed_gradients(const double value, const std::vector< var > &operands, const std::vector< double > &gradients)
This function returns a var for an expression that has the specified value, vector of operands...
Definition: precomputed_gradients.hpp:98
vari.hpp
stan
Definition: log_sum_exp.hpp:8
stan::math::precomputed_gradients_vari::gradients_
double * gradients_
Definition: precomputed_gradients.hpp:25
stan::math::precomputed_gradients_vari::size_
const size_t size_
Definition: precomputed_gradients.hpp:23
stan::math::vari
The variable implementation base class.
Definition: vari.hpp:30
stan::math::var
Independent (input) and dependent (output) variables for gradients.
Definition: var.hpp:31
stan::math::precomputed_gradients_vari::varis_
vari ** varis_
Definition: precomputed_gradients.hpp:24
stan::math::precomputed_gradients_vari
A variable implementation taking a sequence of operands and partial derivatives with respect to the o...
Definition: precomputed_gradients.hpp:21
stan::math::precomputed_gradients_vari::precomputed_gradients_vari
precomputed_gradients_vari(double val, const std::vector< var > &vars, const std::vector< double > &gradients)
Construct a precomputed vari with the specified value, operands, and gradients.
Definition: precomputed_gradients.hpp:58
stan::math::invalid_argument
void invalid_argument(const char *function, const char *name, const T &y, const char *msg1, const char *msg2)
Throw an invalid_argument exception with a consistently formatted message.
Definition: invalid_argument.hpp:31
var.hpp
stan::math::precomputed_gradients_vari::chain
void chain()
Implements the chain rule for this variable, using the prestored operands and gradient.
Definition: precomputed_gradients.hpp:79
stan::math::size
int size(const std::vector< T > &x)
Return the size of the specified standard vector.
Definition: size.hpp:17
stan::math::AutodiffStackStorage
Definition: autodiffstackstorage.hpp:12
stan::math::vari::adj_
double adj_
The adjoint of this variable, which is the partial derivative of this variable with respect to the ro...
Definition: vari.hpp:44
stan::math::precomputed_gradients_vari::precomputed_gradients_vari
precomputed_gradients_vari(double val, size_t size, vari **varis, double *gradients)
Construct a precomputed vari with the specified value, operands, and gradients.
Definition: precomputed_gradients.hpp:37

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