Logarithm of Gamma Function

ASA245, a C++ library which evaluates the logarithm of the gamma function.

ASA245 is Applied Statistics Algorithm 245.


The computer code and data files described and made available on this web page are distributed under the GNU LGPL license.


ASA245 is available in a C version and a C++ version and a FORTRAN90 version and a MATLAB version.

Related Data and Programs:


FN, a C++ library which approximates elementary and special functions using Chebyshev polynomials, by Wayne Fullerton.

GSL, a C++ library which includes many routines for evaluating special functions.

TEST_VALUES, a C++ library which contains sample values for a number of distributions.

TOMS291, a C++ library which evaluates the logarithm of the Gamma function.


  1. Cornelius Lanczos,
    A precision approximation of the gamma function,
    SIAM Journal on Numerical Analysis, B,
    Volume 1, 1964, pages 86-96.
  2. Allan Mcleod,
    Algorithm AS 245: A Robust and Reliable Algorithm for the Logarithm of the Gamma Function,
    Applied Statistics,
    Volume 38, Number 2, 1989, pages 397-402.

Source Code:

Last revised on 31 January 2020.