home *** CD-ROM | disk | FTP | other *** search
/ Frostbyte's 1980s DOS Shareware Collection / floppyshareware.zip / floppyshareware / DOOG / PCSSP1.ZIP / AGLGQUAD.ZIP / QA8.FOR < prev    next >
Text File  |  1985-11-29  |  2KB  |  58 lines
  1. C
  2. C     ..................................................................
  3. C
  4. C        SUBROUTINE QA8
  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 QA8 (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 FUNCTION SUBPROGRAM USED.
  16. C           Y      - THE RESULTING INTEGRAL VALUE.
  17. C
  18. C        REMARKS
  19. C           NONE
  20. C
  21. C        SUBROUTINES AND FUNCTION SUBPROGRAMS REQUIRED
  22. C           THE EXTERNAL FUNCTION SUBPROGRAM FCT(X) MUST BE FURNISHED
  23. C           BY THE USER.
  24. C
  25. C        METHOD
  26. C           EVALUATION IS DONE BY MEANS OF 8-POINT GENERALIZED GAUSSIAN-
  27. C           LAGUERRE QUADRATURE FORMULA, WHICH INTEGRATES EXACTLY,
  28. C           WHENEVER FCT(X) IS A POLYNOMIAL UP TO DEGREE 15.
  29. C           FOR REFERENCE, SEE
  30. C           CONCUS/CASSATT/JAEHNIG/MELBY, TABLES FOR THE EVALUATION OF
  31. C           INTEGRAL(X**BETA*EXP(-X)*F(X), SUMMED OVER X FROM 0 TO
  32. C           INFINITY) BY GAUSS-LAGUERRE QUADRATURE, MTAC, VOL.17,
  33. C           ISS.83 (1963), PP.245-256.
  34. C
  35. C     ..................................................................
  36. C
  37.       SUBROUTINE QA8(FCT,Y)
  38. C
  39. C
  40.       X=21.98427
  41.       Y=.5309615E-9*FCT(X)
  42.       X=14.97262
  43.       Y=Y+.4641962E-6*FCT(X)
  44.       X=10.09332
  45.       Y=Y+.5423720E-4*FCT(X)
  46.       X=6.483145
  47.       Y=Y+.001864568*FCT(X)
  48.       X=3.809476
  49.       Y=Y+.02576062*FCT(X)
  50.       X=1.905114
  51.       Y=Y+.1676201*FCT(X)
  52.       X=.6772491
  53.       Y=Y+.5612949*FCT(X)
  54.       X=.07479188
  55.       Y=Y+1.015859*FCT(X)
  56.       RETURN
  57.       END
  58.