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subroutine dgscale( nn, gold, xdiff, diag, rmin ) |
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c ================================================================== |
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c SUBROUTINE dgscale |
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c ================================================================== |
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c |
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c o computes new preconditioner and writes it to OPWARMD |
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c |
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c o started: ??? not reproducible |
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c |
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c o Version: 2.1.0, 02-Mar-2000: Patrick Heimbach, MIT/EAPS |
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c |
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c ================================================================== |
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c SUBROUTINE dgscale |
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c ================================================================== |
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implicit none |
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#include "blas1.h" |
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integer nn |
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double precision gold(nn), xdiff(nn), diag(nn) |
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integer i |
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double precision r1, rmin, den |
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c----------------------------------------- |
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c read diagonal |
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c----------------------------------------- |
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call dostore( nn, diag, .false., 3 ) |
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r1 = 0. |
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do i = 1, nn |
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r1 = r1 + gold(i)*gold(i)*diag(i) |
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end do |
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r1 = 1.0 / r1 |
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call SSCAL( nn, r1, diag, 1 ) |
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c----------------------------------------- |
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c update the diagonal |
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c (gg is used as an auxiliary vector) |
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c----------------------------------------- |
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den = 0.0 |
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do i = 1, nn |
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cph( |
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if (diag(i).LE.rmin) then |
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cph print *, 'pathei-lsopt: in dgscale; diag = 0 for i=', i |
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diag(i) = rmin |
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end if |
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cph) |
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den = den + xdiff(i)*xdiff(i) / diag(i) |
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end do |
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do i = 1, nn |
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diag(i) = 1./ |
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$ (1./diag(i)+gold(i)**2-(xdiff(i)/diag(i))**2/den) |
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if (diag(i).le.rmin) then |
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diag(i) = rmin |
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endif |
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end do |
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c----------------------------------------- |
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c write diagonal |
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c----------------------------------------- |
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call dostore( nn, diag, .true., 3 ) |
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return |
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end |
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