Stan Math Library  2.20.0
reverse mode automatic differentiation
check_2F1_converges.hpp
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1 #ifndef STAN_MATH_PRIM_SCAL_ERR_CHECK_2F1_CONVERGES_HPP
2 #define STAN_MATH_PRIM_SCAL_ERR_CHECK_2F1_CONVERGES_HPP
3 
8 #include <cmath>
9 #include <limits>
10 #include <sstream>
11 #include <stdexcept>
12 
13 namespace stan {
14 namespace math {
15 
33 template <typename T_a1, typename T_a2, typename T_b1, typename T_z>
34 inline void check_2F1_converges(const char* function, const T_a1& a1,
35  const T_a2& a2, const T_b1& b1, const T_z& z) {
36  using std::fabs;
37  using std::floor;
38 
39  check_not_nan("check_3F2_converges", "a1", a1);
40  check_not_nan("check_3F2_converges", "a2", a2);
41  check_not_nan("check_3F2_converges", "b1", b1);
42  check_not_nan("check_3F2_converges", "z", z);
43 
44  int num_terms = 0;
45  bool is_polynomial = false;
46 
47  if (is_nonpositive_integer(a1) && fabs(a1) >= num_terms) {
48  is_polynomial = true;
49  num_terms = floor(fabs(value_of_rec(a1)));
50  }
51  if (is_nonpositive_integer(a2) && fabs(a2) >= num_terms) {
52  is_polynomial = true;
53  num_terms = floor(fabs(value_of_rec(a2)));
54  }
55 
56  bool is_undefined = is_nonpositive_integer(b1) && fabs(b1) <= num_terms;
57 
58  if (!is_undefined
59  && (is_polynomial || fabs(z) < 1 || (fabs(z) == 1 && b1 > a1 + a2)))
60  return;
61 
62  std::stringstream msg;
63  msg << "called from function '" << function << "', "
64  << "hypergeometric function 2F1 does not meet convergence "
65  << "conditions with given arguments. "
66  << "a1: " << a1 << ", a2: " << a2 << ", "
67  << "b1: " << b1 << ", z: " << z;
68  throw std::domain_error(msg.str());
69 }
70 
71 } // namespace math
72 } // namespace stan
73 #endif
fvar< T > fabs(const fvar< T > &x)
Definition: fabs.hpp:15
double value_of_rec(const fvar< T > &v)
Return the value of the specified variable.
bool is_nonpositive_integer(T x)
Returns true if the input is a nonpositive integer and false otherwise.
void check_not_nan(const char *function, const char *name, const T_y &y)
Check if y is not NaN.
void domain_error(const char *function, const char *name, const T &y, const char *msg1, const char *msg2)
Throw a domain error with a consistently formatted message.
fvar< T > floor(const fvar< T > &x)
Definition: floor.hpp:12
void check_2F1_converges(const char *function, const T_a1 &a1, const T_a2 &a2, const T_b1 &b1, const T_z &z)
Check if the hypergeometric function (2F1) called with supplied arguments will converge, assuming arguments are finite values.

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