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dsconv

  1. C DSCONV    SOURCE    BP208322  20/02/06    21:15:29     10512          
  2. c-----------------------------------------------------------------------
  3. c\BeginDoc
  4. c
  5. c\Name: dsconv
  6. c
  7. c\Description:
  8. c  Convergence testing for the symmetric Arnoldi eigenvalue routine.
  9. c
  10. c\Usage:
  11. c  call dsconv
  12. c     ( N, RITZ, BOUNDS, TOL, NCONV )
  13. c
  14. c\Arguments
  15. c  N       Integer.  (INPUT)
  16. c          Number of Ritz values to check for convergence.
  17. c
  18. c  RITZ    Double precision array of length N.  (INPUT)
  19. c          The Ritz values to be checked for convergence.
  20. c
  21. c  BOUNDS  Double precision array of length N.  (INPUT)
  22. c          Ritz estimates associated with the Ritz values in RITZ.
  23. c
  24. c  TOL     Double precision scalar.  (INPUT)
  25. c          Desired relative accuracy for a Ritz value to be considered
  26. c          "converged".
  27. c
  28. c  NCONV   Integer scalar.  (OUTPUT)
  29. c          Number of "converged" Ritz values.
  30. c
  31. c\EndDoc
  32. c
  33. c-----------------------------------------------------------------------
  34. c
  35. c\BeginLib
  36. c
  37. c\Routines called:
  38. c     arscnd  ARPACK utility routine for timing. -> deleted by BP in 2020
  39. c     dlamch  LAPACK routine that determines machine constants.
  40. c
  41. c\Author
  42. c     Danny Sorensen               Phuong Vu
  43. c     Richard Lehoucq              CRPC / Rice University
  44. c     Dept. of Computational &     Houston, Texas
  45. c     Applied Mathematics
  46. c     Rice University
  47. c     Houston, Texas
  48. c
  49. c\SCCS Information: @(#)
  50. c FILE: sconv.F   SID: 2.4   DATE OF SID: 4/19/96   RELEASE: 2
  51. c
  52. c\Remarks
  53. c     1. Starting with version 2.4, this routine no longer uses the
  54. c        Parlett strategy using the gap conditions.
  55. c
  56. c\EndLib
  57. c
  58. c-----------------------------------------------------------------------
  59. c
  60.       subroutine dsconv (n, ritz, bounds, tol, nconv)
  61. c
  62. c     %----------------------------------------------------%
  63. c     | Include files for debugging and timing information |
  64. c -INC TARTRAK
  65. c     %----------------------------------------------------%
  66. c
  67. c
  68. c     %------------------%
  69. c     | Scalar Arguments |
  70. c     %------------------%
  71. c
  72.       integer    n, nconv
  73.       REAL*8
  74.      &           tol
  75. c       real*8     T0,T1
  76. c
  77. c     %-----------------%
  78. c     | Array Arguments |
  79. c     %-----------------%
  80. c
  81.       REAL*8
  82.      &           ritz(n), bounds(n)
  83. c
  84. c     %---------------%
  85. c     | Local Scalars |
  86. c     %---------------%
  87. c
  88.       integer    i
  89.       REAL*8
  90.      &           temp, eps23
  91. c
  92. c     %-------------------%
  93. c     | External routines |
  94. c     %-------------------%
  95. c
  96.       REAL*8
  98.       external   dlamch
  99.  
  100. c     %---------------------%
  101. **c     | Intrinsic Functions |
  102. **c     %---------------------%
  103. **c
  104. **      intrinsic    abs
  105. **c
  106. **c     %-----------------------%
  107. **c     | Executable Statements |
  108. c     %-----------------------%
  109. c       T0=0.D0
  110. c       T1=0.D0
  111. c
  112. *      call arscnd (t0)
  113. c
  114.       eps23 = dlamch('Epsilon-Machine')
  115.       eps23 = eps23**(2.0D+0 / 3.0D+0)
  116. c
  117.       nconv  = 0
  118.       do 10 i = 1, n
  119. c
  120. c        %-----------------------------------------------------%
  121. c        | The i-th Ritz value is considered "converged"       |
  122. c        | when: bounds(i) .le. TOL*max(eps23, abs(ritz(i)))   |
  123. c        %-----------------------------------------------------%
  124. c
  125.          temp = max( eps23, abs(ritz(i)) )
  126.          if ( bounds(i) .le. tol*temp ) then
  127.             nconv = nconv + 1
  128.          end if
  129. c
  130.    10 continue
  131. c
  132. *      call arscnd (t1)
  133. c       tsconv = tsconv + (t1 - t0)
  134. c
  135. c       return
  136. c
  137. c     %---------------%
  138. c     | End of dsconv |
  139. c     %---------------%
  140. c
  141.       end
  142.  
  143.  
  144.  
  145.  

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