1 #ifndef STAN_MATH_PRIM_SCAL_FUN_GRAD_REG_INC_GAMMA_HPP 2 #define STAN_MATH_PRIM_SCAL_FUN_GRAD_REG_INC_GAMMA_HPP 47 if (z >= a && z >= 8) {
50 T a_minus_one_minus_k = a - 1;
51 T fac = a_minus_one_minus_k;
54 T delta = dfac / zpow;
56 for (
int k = 1; k < 10; ++k) {
57 a_minus_one_minus_k -= 1;
62 dfac = a_minus_one_minus_k * dfac + fac;
63 fac *= a_minus_one_minus_k;
68 "is not converging",
"",
"");
71 return gamma_q(a, z) * (l - dig) +
exp(-z + (a - 1) * l) * S / g;
79 while (
fabs(delta) > precision) {
86 "is not converging",
"",
"");
88 return gamma_p(a, z) * ( dig - l ) +
exp( a * l ) * S / g;
fvar< T > fabs(const fvar< T > &x)
fvar< T > log(const fvar< T > &x)
fvar< T > square(const fvar< T > &x)
fvar< T > exp(const fvar< T > &x)
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.
int is_inf(const fvar< T > &x)
Returns 1 if the input's value is infinite and 0 otherwise.
fvar< T > gamma_p(const fvar< T > &x1, const fvar< T > &x2)
double e()
Return the base of the natural logarithm.
T grad_reg_inc_gamma(T a, T z, T g, T dig, double precision=1e-6)
Gradient of the regularized incomplete gamma functions igamma(a, z)
fvar< T > gamma_q(const fvar< T > &x1, const fvar< T > &x2)