| 1234567891011121314151617181920212223242526272829303132333435363738394041424344 |
- *DECK DGAMR
- DOUBLE PRECISION FUNCTION DGAMR (X)
- C***BEGIN PROLOGUE DGAMR
- C***PURPOSE Compute the reciprocal of the Gamma function.
- C***LIBRARY SLATEC (FNLIB)
- C***CATEGORY C7A
- C***TYPE DOUBLE PRECISION (GAMR-S, DGAMR-D, CGAMR-C)
- C***KEYWORDS FNLIB, RECIPROCAL GAMMA FUNCTION, SPECIAL FUNCTIONS
- C***AUTHOR Fullerton, W., (LANL)
- C***DESCRIPTION
- C
- C DGAMR(X) calculates the double precision reciprocal of the
- C complete Gamma function for double precision argument X.
- C
- C***REFERENCES (NONE)
- C***ROUTINES CALLED DGAMMA, DLGAMS, XERCLR, XGETF, XSETF
- C***REVISION HISTORY (YYMMDD)
- C 770701 DATE WRITTEN
- C 890531 Changed all specific intrinsics to generic. (WRB)
- C 890531 REVISION DATE from Version 3.2
- C 891214 Prologue converted to Version 4.0 format. (BAB)
- C 900727 Added EXTERNAL statement. (WRB)
- C***END PROLOGUE DGAMR
- DOUBLE PRECISION X, ALNGX, SGNGX, DGAMMA
- EXTERNAL DGAMMA
- C***FIRST EXECUTABLE STATEMENT DGAMR
- DGAMR = 0.0D0
- IF (X.LE.0.0D0 .AND. AINT(X).EQ.X) RETURN
- C
- CALL XGETF (IROLD)
- CALL XSETF (1)
- IF (ABS(X).GT.10.0D0) GO TO 10
- DGAMR = 1.0D0/DGAMMA(X)
- CALL XERCLR
- CALL XSETF (IROLD)
- RETURN
- C
- 10 CALL DLGAMS (X, ALNGX, SGNGX)
- CALL XERCLR
- CALL XSETF (IROLD)
- DGAMR = SGNGX * EXP(-ALNGX)
- RETURN
- C
- END
|
