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Text File  |  1985-11-29  |  2KB  |  69 lines
  1. C
  2. C     ..................................................................
  3. C
  4. C        SUBROUTINE DQA12
  5. C
  6. C        PURPOSE
  7. C           TO COMPUTE INTEGRAL(EXP(-X)*FCT(X)/SQRT(X), SUMMED OVER X
  8. C                               FROM 0 TO INFINITY).
  9. C
  10. C        USAGE
  11. C           CALL DQA12 (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 12-POINT GENERALIZED GAUSS-
  28. C           LAGUERRE QUADRATURE FORMULA, WHICH INTEGRATES EXACTLY
  29. C           WHENEVER FCT(X) IS A POLYNOMIAL UP TO DEGREE 23.
  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.15-16.
  35. C
  36. C     ..................................................................
  37. C
  38.       SUBROUTINE DQA12(FCT,Y)
  39. C
  40. C
  41.       DOUBLE PRECISION X,Y,FCT
  42. C
  43.       X=.36191360360615602D2
  44.       Y=.33287369929782177D-15*FCT(X)
  45.       X=.27661108779846090D2
  46.       Y=Y+.13169240486156340D-11*FCT(X)
  47.       X=.21396755936166109D2
  48.       Y=Y+.60925085399751278D-9*FCT(X)
  49.       X=.16432195087675313D2
  50.       Y=Y+.8037942349882859D-7*FCT(X)
  51.       X=.12390447963809471D2
  52.       Y=Y+.43164914098046673D-5*FCT(X)
  53.       X=.9075434230961203D1
  54.       Y=Y+.11377383272808760D-3*FCT(X)
  55.       X=.63699753880306349D1
  56.       Y=Y+.16473849653768349D-2*FCT(X)
  57.       X=.41984156448784132D1
  58.       Y=Y+.14096711620145342D-1*FCT(X)
  59.       X=.25098480972321280D1
  60.       Y=Y+.7489094100646149D-1*FCT(X)
  61.       X=.12695899401039615D1
  62.       Y=Y+.25547924356911832D0*FCT(X)
  63.       X=.45450668156378028D0
  64.       Y=Y+.57235907069288604D0*FCT(X)
  65.       X=.50361889117293951D-1
  66.       Y=Y+.8538623277373985D0*FCT(X)
  67.       RETURN
  68.       END
  69.