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  1. C JACOBF SOURCE CHAT 05/01/13 00:48:23 5004
  2. C
  3. SUBROUTINE JACOBF (POLY,PDER,POLYM1,PDERM1,POLYM2,PDERM2,
  4. $ N,ALP,BET,X)
  5. C--------------------------------------------------------------------
  6. C
  7. C Computes the Jacobi polynomial (POLY) and its derivative (PDER)
  8. C of degree N at X.
  9. C
  10. C--------------------------------------------------------------------
  11. IMPLICIT INTEGER(I-N)
  12. IMPLICIT REAL*8 (A-H,O-Z)
  13. APB = ALP+BET
  14. POLY = 1.D0
  15. PDER = 0.D0
  16. IF (N .EQ. 0) RETURN
  17. POLYL = POLY
  18. PDERL = PDER
  19. POLY = (ALP-BET+(APB+2.D0)*X)/2.D0
  20. PDER = (APB+2.D0)/2.D0
  21. IF (N .EQ. 1) RETURN
  22. DO 20 K=2,N
  23. DK =K
  24. A1 = 2.D0*DK*(DK+APB)*(2.D0*DK+APB-2.D0)
  25. A2 = (2.D0*DK+APB-1.D0)*(ALP**2-BET**2)
  26. B3 = (2.D0*DK+APB-2.D0)
  27. A3 = B3*(B3+1.D0)*(B3+2.D0)
  28. A4 = 2.D0*(DK+ALP-1.D0)*(DK+BET-1.D0)*(2.D0*DK+APB)
  29. POLYN = ((A2+A3*X)*POLY-A4*POLYL)/A1
  30. PDERN = ((A2+A3*X)*PDER-A4*PDERL+A3*POLY)/A1
  31. PSAVE = POLYL
  32. PDSAVE = PDERL
  33. POLYL = POLY
  34. POLY = POLYN
  35. PDERL = PDER
  36. PDER = PDERN
  37. 20 CONTINUE
  38. POLYM1 = POLYL
  39. PDERM1 = PDERL
  40. POLYM2 = PSAVE
  41. PDERM2 = PDSAVE
  42. RETURN
  43. END
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