algams.f 1.2 KB

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  1. *DECK ALGAMS
  2. SUBROUTINE ALGAMS (X, ALGAM, SGNGAM)
  3. C***BEGIN PROLOGUE ALGAMS
  4. C***PURPOSE Compute the logarithm of the absolute value of the Gamma
  5. C function.
  6. C***LIBRARY SLATEC (FNLIB)
  7. C***CATEGORY C7A
  8. C***TYPE SINGLE PRECISION (ALGAMS-S, DLGAMS-D)
  9. C***KEYWORDS ABSOLUTE VALUE OF THE LOGARITHM OF THE GAMMA FUNCTION,
  10. C FNLIB, SPECIAL FUNCTIONS
  11. C***AUTHOR Fullerton, W., (LANL)
  12. C***DESCRIPTION
  13. C
  14. C Evaluates the logarithm of the absolute value of the gamma
  15. C function.
  16. C X - input argument
  17. C ALGAM - result
  18. C SGNGAM - is set to the sign of GAMMA(X) and will
  19. C be returned at +1.0 or -1.0.
  20. C
  21. C***REFERENCES (NONE)
  22. C***ROUTINES CALLED ALNGAM
  23. C***REVISION HISTORY (YYMMDD)
  24. C 770701 DATE WRITTEN
  25. C 890531 Changed all specific intrinsics to generic. (WRB)
  26. C 890531 REVISION DATE from Version 3.2
  27. C 891214 Prologue converted to Version 4.0 format. (BAB)
  28. C***END PROLOGUE ALGAMS
  29. C***FIRST EXECUTABLE STATEMENT ALGAMS
  30. ALGAM = ALNGAM(X)
  31. SGNGAM = 1.0
  32. IF (X.GT.0.0) RETURN
  33. C
  34. INT = MOD (-AINT(X), 2.0) + 0.1
  35. IF (INT.EQ.0) SGNGAM = -1.0
  36. C
  37. RETURN
  38. END