/* Function: esl_rnd_Gamma()
* Synopsis: Returns a random deviate from a Gamma(a, 1) distribution.
* Incept: SRE, Wed Apr 17 13:10:03 2002 [St. Louis]
*
* Purpose: Return a random deviate distributed as Gamma(a, 1.)
* \citep[pp. 133--134]{Knu-81a}.
*
* The implementation follows not only Knuth \citep{Knu-81a},
* but also relied on examination of the implementation in
* the GNU Scientific Library (libgsl) \citep{Galassi06}.
*
* Args: r - random number generation seed
* a - order of the gamma function; a > 0
*
* Throws: <eslEINVAL> for $a <= 0$.
*/
double
esl_rnd_Gamma(ESL_RANDOMNESS *r, double a)
{
double aint;
aint = floor(a);
if (a == aint && a < 12.)
return gamma_integer(r, (unsigned int) a);
else if (a > 3.)
return gamma_ahrens(r, a);
else if (a < 1.)
return gamma_fraction(r, a);
else
return gamma_integer(r, aint) + gamma_fraction(r, a-aint);
return eslOK;
}
int
main (int argc, char *argv[])
{
MPFR_TEST_USE_RANDS ();
tests_start_mpfr ();
special ();
special_overflow ();
test_generic (2, 100, 2);
gamma_integer ();
data_check ("data/gamma", mpfr_gamma, "mpfr_gamma");
tests_end_mpfr ();
return 0;
}
int
main (int argc, char *argv[])
{
tests_start_mpfr ();
special ();
special_overflow ();
exprange ();
tiny (argc == 1);
test_generic (2, 100, 2);
gamma_integer ();
test20071231 ();
test20100709 ();
data_check ("data/gamma", mpfr_gamma, "mpfr_gamma");
tests_end_mpfr ();
return 0;
}
