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inv_gamma_ccdf_log.hpp
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1 #ifndef STAN_MATH_PRIM_SCAL_PROB_INV_GAMMA_CCDF_LOG_HPP
2 #define STAN_MATH_PRIM_SCAL_PROB_INV_GAMMA_CCDF_LOG_HPP
3
4 #include <boost/random/gamma_distribution.hpp>
5 #include <boost/random/variate_generator.hpp>
6 #include <stan/math/prim/scal/meta/OperandsAndPartials.hpp>
7 #include <stan/math/prim/scal/err/check_consistent_sizes.hpp>
8 #include <stan/math/prim/scal/err/check_greater_or_equal.hpp>
9 #include <stan/math/prim/scal/err/check_less_or_equal.hpp>
10 #include <stan/math/prim/scal/err/check_nonnegative.hpp>
11 #include <stan/math/prim/scal/err/check_not_nan.hpp>
12 #include <stan/math/prim/scal/err/check_positive_finite.hpp>
13 #include <stan/math/prim/scal/fun/constants.hpp>
14 #include <stan/math/prim/scal/fun/value_of.hpp>
15 #include <stan/math/prim/scal/fun/lgamma.hpp>
16 #include <stan/math/prim/scal/fun/gamma_q.hpp>
17 #include <stan/math/prim/scal/fun/digamma.hpp>
18 #include <stan/math/prim/scal/meta/length.hpp>
19 #include <stan/math/prim/scal/meta/is_constant_struct.hpp>
20 #include <stan/math/prim/scal/meta/VectorView.hpp>
21 #include <stan/math/prim/scal/meta/VectorBuilder.hpp>
22 #include <stan/math/prim/scal/meta/partials_return_type.hpp>
23 #include <stan/math/prim/scal/meta/return_type.hpp>
24 #include <stan/math/prim/scal/fun/grad_reg_inc_gamma.hpp>
25 #include <stan/math/prim/scal/meta/include_summand.hpp>
26 #include <cmath>
27 #include <limits>
28
29 namespace stan {
30
31 namespace math {
32
33 template <typename T_y, typename T_shape, typename T_scale>
34 typename return_type<T_y, T_shape, T_scale>::type
35 inv_gamma_ccdf_log(const T_y& y, const T_shape& alpha,
36 const T_scale& beta) {
37 typedef typename stan::partials_return_type<T_y, T_shape, T_scale>::type
38 T_partials_return;
39
40 // Size checks
41 if (!(stan::length(y) && stan::length(alpha) && stan::length(beta)))
42 return 0.0;
43
44 // Error checks
45 static const char* function("stan::math::inv_gamma_ccdf_log");
46
47 using stan::math::check_positive_finite;
48 using stan::math::check_not_nan;
49 using stan::math::check_consistent_sizes;
50 using stan::math::check_greater_or_equal;
51 using stan::math::check_less_or_equal;
52 using stan::math::check_nonnegative;
53 using stan::math::value_of;
54 using boost::math::tools::promote_args;
55 using std::exp;
56
57 T_partials_return P(0.0);
58
59 check_positive_finite(function, "Shape parameter", alpha);
60 check_positive_finite(function, "Scale parameter", beta);
61 check_not_nan(function, "Random variable", y);
62 check_nonnegative(function, "Random variable", y);
63 check_consistent_sizes(function,
64 "Random variable", y,
65 "Shape parameter", alpha,
66 "Scale Parameter", beta);
67
68 // Wrap arguments in vectors
69 VectorView<const T_y> y_vec(y);
70 VectorView<const T_shape> alpha_vec(alpha);
71 VectorView<const T_scale> beta_vec(beta);
72 size_t N = max_size(y, alpha, beta);
73
74 OperandsAndPartials<T_y, T_shape, T_scale>
75 operands_and_partials(y, alpha, beta);
76
77 // Explicit return for extreme values
78 // The gradients are technically ill-defined, but treated as zero
79
80 for (size_t i = 0; i < stan::length(y); i++) {
81 if (value_of(y_vec[i]) == 0)
82 return operands_and_partials.to_var(0.0, y, alpha, beta);
83 }
84
85 // Compute ccdf_log and its gradients
86 using stan::math::gamma_q;
87 using stan::math::digamma;
88 using boost::math::tgamma;
89 using std::exp;
90 using std::pow;
91 using std::log;
92
93 // Cache a few expensive function calls if nu is a parameter
94 VectorBuilder<!is_constant_struct<T_shape>::value,
95 T_partials_return, T_shape> gamma_vec(stan::length(alpha));
96 VectorBuilder<!is_constant_struct<T_shape>::value,
97 T_partials_return, T_shape>
98 digamma_vec(stan::length(alpha));
99
100 if (!is_constant_struct<T_shape>::value) {
101 for (size_t i = 0; i < stan::length(alpha); i++) {
102 const T_partials_return alpha_dbl = value_of(alpha_vec[i]);
103 gamma_vec[i] = tgamma(alpha_dbl);
104 digamma_vec[i] = digamma(alpha_dbl);
105 }
106 }
107
108 // Compute vectorized ccdf_log and gradient
109 for (size_t n = 0; n < N; n++) {
110 // Explicit results for extreme values
111 // The gradients are technically ill-defined, but treated as zero
112 if (value_of(y_vec[n]) == std::numeric_limits<double>::infinity())
113 return operands_and_partials.to_var(stan::math::negative_infinity(),
114 y, alpha, beta);
115
116 // Pull out values
117 const T_partials_return y_dbl = value_of(y_vec[n]);
118 const T_partials_return y_inv_dbl = 1.0 / y_dbl;
119 const T_partials_return alpha_dbl = value_of(alpha_vec[n]);
120 const T_partials_return beta_dbl = value_of(beta_vec[n]);
121
122 // Compute
123 const T_partials_return Pn = 1.0 - gamma_q(alpha_dbl, beta_dbl
124 * y_inv_dbl);
125
126 P += log(Pn);
127
128 if (!is_constant_struct<T_y>::value)
129 operands_and_partials.d_x1[n] -= beta_dbl * y_inv_dbl * y_inv_dbl
130 * exp(-beta_dbl * y_inv_dbl) * pow(beta_dbl * y_inv_dbl,
131 alpha_dbl-1)
132 / tgamma(alpha_dbl) / Pn;
133 if (!is_constant_struct<T_shape>::value)
134 operands_and_partials.d_x2[n]
135 -= stan::math::grad_reg_inc_gamma(alpha_dbl, beta_dbl
136 * y_inv_dbl, gamma_vec[n],
137 digamma_vec[n]) / Pn;
138 if (!is_constant_struct<T_scale>::value)
139 operands_and_partials.d_x3[n] += y_inv_dbl
140 * exp(-beta_dbl * y_inv_dbl)
141 * pow(beta_dbl * y_inv_dbl, alpha_dbl-1)
142 / tgamma(alpha_dbl) / Pn;
143 }
144
145 return operands_and_partials.to_var(P, y, alpha, beta);
146 }
147 }
148 }
149
150 #endif
check_not_nan.hpp
lgamma.hpp
stan::math::check_greater_or_equal
bool check_greater_or_equal(const char *function, const char *name, const T_y &y, const T_low &low)
Return true if y is greater or equal than low.
Definition: check_greater_or_equal.hpp:84
stan::math::check_not_nan
bool check_not_nan(const char *function, const char *name, const T_y &y)
Return true if y is not NaN.
Definition: check_not_nan.hpp:63
check_positive_finite.hpp
stan::math::value_of
T value_of(const fvar< T > &v)
Return the value of the specified variable.
Definition: value_of.hpp:16
digamma.hpp
stan::math::log
fvar< T > log(const fvar< T > &x)
Definition: log.hpp:15
stan::length
size_t length(const std::vector< T > &x)
Definition: length.hpp:10
stan::math::OperandsAndPartials::to_var
T_return_type to_var(T_partials_return logp, const T1 &x1=0, const T2 &x2=0, const T3 &x3=0, const T4 &x4=0, const T5 &x5=0, const T6 &x6=0)
Definition: OperandsAndPartials.hpp:322
stan::math::grad_reg_inc_gamma
T grad_reg_inc_gamma(T a, T z, T g, T dig, T precision=1e-6)
Definition: grad_reg_inc_gamma.hpp:15
return_type.hpp
gamma_q.hpp
VectorView.hpp
include_summand.hpp
stan::math::OperandsAndPartials::d_x1
VectorView< T_partials_return, is_vector< T1 >::value, is_constant_struct< T1 >::value > d_x1
Definition: OperandsAndPartials.hpp:253
check_nonnegative.hpp
stan::is_constant_struct
Metaprogram to determine if a type has a base scalar type that can be assigned to type double...
Definition: is_constant_struct.hpp:16
check_less_or_equal.hpp
stan::math::exp
fvar< T > exp(const fvar< T > &x)
Definition: exp.hpp:10
stan::math::OperandsAndPartials::d_x3
VectorView< T_partials_return, is_vector< T3 >::value, is_constant_struct< T3 >::value > d_x3
Definition: OperandsAndPartials.hpp:259
stan::math::OperandsAndPartials
A variable implementation that stores operands and derivatives with respect to the variable...
Definition: OperandsAndPartials.hpp:238
OperandsAndPartials.hpp
stan::max_size
size_t max_size(const T1 &x1, const T2 &x2)
Definition: max_size.hpp:9
VectorBuilder.hpp
stan::math::inv_gamma_ccdf_log
return_type< T_y, T_shape, T_scale >::type inv_gamma_ccdf_log(const T_y &y, const T_shape &alpha, const T_scale &beta)
Definition: inv_gamma_ccdf_log.hpp:35
partials_return_type.hpp
stan::math::check_less_or_equal
bool check_less_or_equal(const char *function, const char *name, const T_y &y, const T_high &high)
Return true if y is less or equal to high.
Definition: check_less_or_equal.hpp:81
length.hpp
grad_reg_inc_gamma.hpp
stan::VectorBuilder
Definition: VectorBuilder.hpp:61
constants.hpp
stan::math::check_consistent_sizes
bool check_consistent_sizes(const char *function, const char *name1, const T1 &x1, const char *name2, const T2 &x2)
Return true if the dimension of x1 is consistent with x2.
Definition: check_consistent_sizes.hpp:31
stan::math::OperandsAndPartials::d_x2
VectorView< T_partials_return, is_vector< T2 >::value, is_constant_struct< T2 >::value > d_x2
Definition: OperandsAndPartials.hpp:256
is_constant_struct.hpp
stan::math::pow
fvar< T > pow(const fvar< T > &x1, const fvar< T > &x2)
Definition: pow.hpp:18
stan::math::check_nonnegative
bool check_nonnegative(const char *function, const char *name, const T_y &y)
Return true if y is non-negative.
Definition: check_nonnegative.hpp:66
check_greater_or_equal.hpp
value_of.hpp
stan::math::tgamma
fvar< T > tgamma(const fvar< T > &x)
Definition: tgamma.hpp:15
stan::VectorView
VectorView is a template metaprogram that takes its argument and allows it to be used like a vector...
Definition: VectorView.hpp:41
stan::partials_return_type::type
boost::math::tools::promote_args< typename partials_type< typename scalar_type< T1 >::type >::type, typename partials_type< typename scalar_type< T2 >::type >::type, typename partials_type< typename scalar_type< T3 >::type >::type, typename partials_type< typename scalar_type< T4 >::type >::type, typename partials_type< typename scalar_type< T5 >::type >::type, typename partials_type< typename scalar_type< T6 >::type >::type >::type type
Definition: partials_return_type.hpp:26
stan::math::gamma_q
fvar< T > gamma_q(const fvar< T > &x1, const fvar< T > &x2)
Definition: gamma_q.hpp:15
check_consistent_sizes.hpp
stan::math::check_positive_finite
bool check_positive_finite(const char *function, const char *name, const T_y &y)
Return true if y is positive and finite.
Definition: check_positive_finite.hpp:28
stan::math::negative_infinity
double negative_infinity()
Return negative infinity.
Definition: constants.hpp:132
stan::math::digamma
fvar< T > digamma(const fvar< T > &x)
Definition: digamma.hpp:16

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