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  1. C GLSQ SOURCE CHAT 05/01/13 00:18:31 5004
  2. *********************************************************************
  3. SUBROUTINE GLSQ(A,X,IL,N,M,ALPHA,E1,E2,M50)
  4. C
  5. C LEAST SQUARES SOLUTION OF A LINEAR SYSTEM
  6. C-----------------------------------------------------------------------
  7. C
  8. IMPLICIT INTEGER(I-N)
  9. IMPLICIT REAL*8(A-H,O-Z)
  10. DIMENSION A(M50,M50), X(*)
  11. INTEGER IL(*)
  12. C
  13. C-----------------------------------------------------------------------
  14. C
  15. MPLUS1 = M + 1
  16. I = 1
  17. C
  18. DO 50 K = 1, M
  19. IL(K) = 0
  20. IF(I - N) 10, 40, 50
  21. C
  22. 10 IPLUS1 = I + 1
  23. DO 30 J = IPLUS1, N
  24. IF(ABS(A(J,K)) .LE. E1) GO TO 30
  25. T1 = SQRT(A(J,K)**2 + A(I,K)**2)
  26. S = A(J,K) / T1
  27. C = A(I,K) / T1
  28. C
  29. DO 20 L = K, MPLUS1
  30. T2 = + C * A(I,L) + S * A(J,L)
  31. A(J,L) = - S * A(I,L) + C * A(J,L)
  32. A(I,L) = T2
  33. 20 CONTINUE
  34. C
  35. 30 CONTINUE
  36. C
  37. 40 IF(ABS(A(I,K)) .LE. E2) GO TO 50
  38. IL(K) = I
  39. I = I + 1
  40. 50 CONTINUE
  41. C
  42. SUM = 0.0
  43. IF(I .GT. N) GO TO 70
  44. C
  45. DO 60 J = I, N
  46. SUM = SUM + A(J,MPLUS1)**2
  47. 60 CONTINUE
  48. C
  49. 70 ALPHA = SQRT(SUM)
  50. X(MPLUS1) = - 1.0
  51. C
  52. DO 90 J = 1, M
  53. I = MPLUS1 - J
  54. X(I) = 0.0
  55. L = IL(I)
  56. IF(L .EQ. 0) GO TO 90
  57. IPLUS1 = I + 1
  58. SUM = 0.0
  59. C
  60. DO 80 K = IPLUS1, MPLUS1
  61. SUM = SUM + A(L,K) * X(K)
  62. 80 CONTINUE
  63. C
  64. X(I) = - SUM / A(L,I)
  65. 90 CONTINUE
  66. C
  67. RETURN
  68. END
  69.  
  70.  

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