SLATEC Routines --- DGAMRN ---

*DECK DGAMRN
      DOUBLE PRECISION FUNCTION DGAMRN (X)
C***BEGIN PROLOGUE  DGAMRN
C***SUBSIDIARY
C***PURPOSE  Subsidiary to DBSKIN
C***LIBRARY   SLATEC
C***TYPE      DOUBLE PRECISION (GAMRN-S, DGAMRN-D)
C***AUTHOR  Amos, D. E., (SNLA)
C***DESCRIPTION
C
C     Abstract   * A Double Precision Routine *
C         DGAMRN computes the GAMMA function ratio GAMMA(X)/GAMMA(X+0.5)
C         for real X.gt.0. If X.ge.XMIN, an asymptotic expansion is
C         evaluated. If X.lt.XMIN, an integer is added to X to form a
C         new value of X.ge.XMIN and the asymptotic expansion is eval-
C         uated for this new value of X. Successive application of the
C         recurrence relation
C
C                      W(X)=W(X+1)*(1+0.5/X)
C
C         reduces the argument to its original value. XMIN and comp-
C         utational tolerances are computed as a function of the number
C         of digits carried in a word by calls to I1MACH and D1MACH.
C         However, the computational accuracy is limited to the max-
C         imum of unit roundoff (=D1MACH(4)) and 1.0D-18 since critical
C         constants are given to only 18 digits.
C
C         Input      X is Double Precision
C           X      - Argument, X.gt.0.0D0
C
C         Output      DGAMRN is DOUBLE PRECISION
C           DGAMRN  - Ratio  GAMMA(X)/GAMMA(X+0.5)
C
C***SEE ALSO  DBSKIN
C***REFERENCES  Y. L. Luke, The Special Functions and Their
C                 Approximations, Vol. 1, Math In Sci. And
C                 Eng. Series 53, Academic Press, New York, 1969,
C                 pp. 34-35.
C***ROUTINES CALLED  D1MACH, I1MACH
C***REVISION HISTORY  (YYMMDD)
C   820601  DATE WRITTEN
C   890531  Changed all specific intrinsics to generic.  (WRB)
C   890911  Removed unnecessary intrinsics.  (WRB)
C   891214  Prologue converted to Version 4.0 format.  (BAB)
C   900328  Added TYPE section.  (WRB)
C   910722  Updated AUTHOR section.  (ALS)
C   920520  Added REFERENCES section.  (WRB)
C***END PROLOGUE  DGAMRN