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  1. C PVECTO SOURCE CB215821 16/04/21 21:18:09 8920
  2. c---------------------------------------------------------------------
  3. c
  4. SUBROUTINE PVECTO (S, XL, V, COM)
  5. c
  6. c=====================================================================
  7. c =
  8. c This routine calculates one eigenvector. =
  9. c =
  10. c Input: xl eigenvalue =
  11. c s (6) original matrix =
  12. c Output: v (3) eigenvector =
  13. c =
  14. c Note: s = (Sxx, Syy, Szz, Sxy, Sxz, Syz) =
  15. c =
  16. c=====================================================================
  17. IMPLICIT INTEGER(I-N)
  18. real*8 s (6), v (3), xl, com
  19. c
  20. real*8 tol, x1, x2, x3, x4, x5, x6, xn, det, deti, v1, v2
  21. c
  22. data tol / 1.0 d-07 /
  23. c
  24. x1 = s (1) - xl
  25. x2 = s (2) - xl
  26. x3 = s (3) - xl
  27. x4 = s (4)
  28. x5 = s (6)
  29. x6 = s (5)
  30. c
  31. det = x1 * x2 - x4 **2
  32. if (ABS(det/com) .gt. tol) then
  33. deti = 1.0 d0 / det
  34. v1 = (x4 * x5 - x6 * x2) * deti
  35. v2 = (x6 * x4 - x5 * x1) * deti
  36. xn = 1.0 d0 / SQRT(v1**2+v2**2+1.0d0)
  37. v (1) = v1 * xn
  38. v (2) = v2 * xn
  39. v (3) = xn
  40. return
  41. end if
  42. c
  43. det = x4 * x5 - x6 * x2
  44. if (ABS(det/com) .gt. tol) then
  45. v1 = (x6 * x4 - x5 * x1) / det
  46. xn = 1.0 d0 / SQRT(v1**2+1.0d0)
  47. v (1) = xn
  48. v (2) = v1 * xn
  49. v (3) = 0.0 d0
  50. return
  51. end if
  52. c
  53. det = x1 * x5 - x4 * x6
  54. if (ABS(det/com) .gt. tol) then
  55. v (1) = 0.0 d0
  56. v (2) = 1.0 d0
  57. v (3) = 0.0 d0
  58. return
  59. end if
  60. c
  61. det = x4 * x3 - x5 * x6
  62. if (ABS(det/com) .gt. tol) then
  63. v1 = (x5 **2 - x2 * x3) / det
  64. xn = 1.0 d0 / SQRT(v1**2+1.0d0)
  65. v (1) = v1 * xn
  66. v (2) = xn
  67. v (3) = 0.0 d0
  68. return
  69. end if
  70. c
  71. det = x2 * x3 - x5 **2
  72. if (ABS(det/com) .gt. tol) then
  73. v (1) = 1.0 d0
  74. v (2) = 0.0 d0
  75. v (3) = 0.0 d0
  76. return
  77. end if
  78. c
  79. v (1) = 0.0 d0
  80. v (2) = 1.0 d0
  81. v (3) = 0.0 d0
  82. c
  83. end
  84.  
  85.  
  86.  
  87.  

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