GAMRN(3)

SYNOPSIS
REAL FUNCTION GAMRN (X)

NAME
gamrn - Subsidiary to BSKIN

LIBRARY
SLATEC

TYPE
SINGLE PRECISION (GAMRN-S, DGAMRN-D)

AUTHOR
Amos, D. E., (SNLA)

DESCRIPTION
Abstract GAMRN computes the GAMMA function ratio GAMMA(X)/GAMMA(X+0.5) for real X.gt.0. If X.ge.XMIN, an asymptotic expansion is evaluated. If X.lt.XMIN, an integer is added to X to form a new value of X.ge.XMIN and the asymptotic expansion is eval- uated for this new value of X. Successive application of the recurrence relation W(X)=W(X+1)*(1+0.5/X) reduces the argument to its original value. XMIN and comp- utational tolerances are computed as a function of the number of digits carried in a word by calls to I1MACH and R1MACH. However, the computational accuracy is limited to the max- imum of unit roundoff (=R1MACH(4)) and 1.0E-18 since critical constants are given to only 18 digits. Input X - Argument, X.gt.0.0 OUTPUT GAMRN - Ratio GAMMA(X)/GAMMA(X+0.5)

SEE ALSO
BSKIN

REFERENCES
Y. L. Luke, The Special Functions and Their Approximations, Vol. 1, Math In Sci. And Eng. Series 53, Academic Press, New York, 1969, pp. 34-35.

ROUTINES CALLED
I1MACH, R1MACH

REVISION HISTORY (YYMMDD)
820601 DATE WRITTEN
890531 Changed all specific intrinsics to generic. (WRB)
891214 Prologue converted to Version 4.0 format. (BAB)
900328 Added TYPE section. (WRB)
910722 Updated AUTHOR section. (ALS)
920520 Added REFERENCES section. (WRB)