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Text File  |  1985-11-29  |  3KB  |  77 lines
  1. C
  2. C     ..................................................................
  3. C
  4. C        SUBROUTINE DQL16
  5. C
  6. C        PURPOSE
  7. C           TO COMPUTE INTEGRAL(EXP(-X)*FCT(X), SUMMED OVER X
  8. C                               FROM 0 TO INFINITY).
  9. C
  10. C        USAGE
  11. C           CALL DQL16 (FCT,Y)
  12. C           PARAMETER FCT REQUIRES AN EXTERNAL STATEMENT
  13. C
  14. C        DESCRIPTION OF PARAMETERS
  15. C           FCT    - THE NAME OF AN EXTERNAL DOUBLE PRECISION FUNCTION
  16. C                    SUBPROGRAM USED.
  17. C           Y      - THE RESULTING DOUBLE PRECISION INTEGRAL VALUE.
  18. C
  19. C        REMARKS
  20. C           NONE
  21. C
  22. C        SUBROUTINES AND FUNCTION SUBPROGRAMS REQUIRED
  23. C           THE EXTERNAL DOUBLE PRECISION FUNCTION SUBPROGRAM FCT(X)
  24. C           MUST BE FURNISHED BY THE USER.
  25. C
  26. C        METHOD
  27. C           EVALUATION IS DONE BY MEANS OF 16-POINT GAUSSIAN-LAGUERRE
  28. C           QUADRATURE FORMULA, WHICH INTEGRATES EXACTLY,
  29. C           WHENEVER FCT(X) IS A POLYNOMIAL UP TO DEGREE 31.
  30. C           FOR REFERENCE, SEE
  31. C           SHAO/CHEN/FRANK, TABLES OF ZEROS AND GAUSSIAN WEIGHTS OF
  32. C           CERTAIN ASSOCIATED LAGUERRE POLYNOMIALS AND THE RELATED
  33. C           GENERALIZED HERMITE POLYNOMIALS, IBM TECHNICAL REPORT
  34. C           TR00.1100 (MARCH 1964), PP.24-25.
  35. C
  36. C     ..................................................................
  37. C
  38.       SUBROUTINE DQL16(FCT,Y)
  39. C
  40. C
  41.       DOUBLE PRECISION X,Y,FCT
  42. C
  43.       X=.51701160339543318D2
  44.       Y=.41614623703728552D-21*FCT(X)
  45.       X=.41940452647688333D2
  46.       Y=Y+.50504737000355128D-17*FCT(X)
  47.       X=.34583398702286626D2
  48.       Y=Y+.62979670025178678D-14*FCT(X)
  49.       X=.28578729742882140D2
  50.       Y=Y+.21270790332241030D-11*FCT(X)
  51.       X=.23515905693991909D2
  52.       Y=Y+.28623502429738816D-9*FCT(X)
  53.       X=.19180156856753135D2
  54.       Y=Y+.18810248410796732D-7*FCT(X)
  55.       X=.15441527368781617D2
  56.       Y=Y+.68283193308711996D-6*FCT(X)
  57.       X=.12214223368866159D2
  58.       Y=Y+.14844586873981299D-4*FCT(X)
  59.       X=.9438314336391939D1
  60.       Y=Y+.20427191530827846D-3*FCT(X)
  61.       X=.70703385350482341D1
  62.       Y=Y+.18490709435263109D-2*FCT(X)
  63.       X=.50780186145497679D1
  64.       Y=Y+.11299900080339453D-1*FCT(X)
  65.       X=.34370866338932066D1
  66.       Y=Y+.47328928694125219D-1*FCT(X)
  67.       X=.21292836450983806D1
  68.       Y=Y+.13629693429637754D0*FCT(X)
  69.       X=.11410577748312269D1
  70.       Y=Y+.26579577764421415D0*FCT(X)
  71.       X=.46269632891508083D0
  72.       Y=Y+.33105785495088417D0*FCT(X)
  73.       X=.8764941047892784D-1
  74.       Y=Y+.20615171495780099D0*FCT(X)
  75.       RETURN
  76.       END
  77.