Module PSI in SPECFUN

General Information

Evaluates the logarithmic derivative of the gamma function, psi(x) = d/dx (gamma(x)) / gamma(x) = d/dx (ln gamma(x)) for real x, where either -xmax1 < x < -xmin (x not a negative integer), or xmin < x. Uses rational approximations that are theoretically accurate to 20 significant decimal digits.

Usage

S = PSI(X)

Classification

C7c	Psi function

Type

subroutine in SPECFUN package

Language

Fortran

Availability

Public domain, Portable

Precision

Single & Double Precision

Download from NETLIB; Public access repository

Location

The University of Tennessee at Knoxville and Bell Laboratories

Contact

Jack Dongarra, ORNL (dongarra@cs.utk.edu) and Eric Grosse, Bell Labs (ehg@research.att.com)