/[MITgcm]/MITgcm_contrib/ecco_utils/ecco_v4_release3_optimization/lsopt/dgscale.F
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Revision 1.1 - (hide annotations) (download)
Wed Jan 3 17:13:47 2018 UTC (7 years, 6 months ago) by ou.wang
Branch: MAIN
CVS Tags: HEAD
Check in the optimization used in ECCO v4r3

1 ou.wang 1.1
2     subroutine dgscale( nn, gold, xdiff, diag, rmin )
3    
4    
5     c ==================================================================
6     c SUBROUTINE dgscale
7     c ==================================================================
8     c
9     c o computes new preconditioner and writes it to OPWARMD
10     c
11     c o started: ??? not reproducible
12     c
13     c o Version: 2.1.0, 02-Mar-2000: Patrick Heimbach, MIT/EAPS
14     c
15     c ==================================================================
16     c SUBROUTINE dgscale
17     c ==================================================================
18    
19     implicit none
20    
21     #include "blas1.h"
22    
23     integer nn
24     double precision gold(nn), xdiff(nn), diag(nn)
25    
26     integer i
27     double precision r1, rmin, den
28    
29    
30     c-----------------------------------------
31     c read diagonal
32     c-----------------------------------------
33     call dostore( nn, diag, .false., 3 )
34    
35     r1 = 0.
36     do i = 1, nn
37     r1 = r1 + gold(i)*gold(i)*diag(i)
38     end do
39     r1 = 1.0 / r1
40    
41     call SSCAL( nn, r1, diag, 1 )
42    
43     c-----------------------------------------
44     c update the diagonal
45     c (gg is used as an auxiliary vector)
46     c-----------------------------------------
47    
48     den = 0.0
49    
50     do i = 1, nn
51     cph(
52     if (diag(i).LE.rmin) then
53     cph print *, 'pathei-lsopt: in dgscale; diag = 0 for i=', i
54     diag(i) = rmin
55     end if
56     cph)
57     den = den + xdiff(i)*xdiff(i) / diag(i)
58     end do
59    
60     do i = 1, nn
61     diag(i) = 1./
62     $ (1./diag(i)+gold(i)**2-(xdiff(i)/diag(i))**2/den)
63     if (diag(i).le.rmin) then
64     diag(i) = rmin
65     endif
66     end do
67    
68     c-----------------------------------------
69     c write diagonal
70     c-----------------------------------------
71     call dostore( nn, diag, .true., 3 )
72    
73     return
74     end

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