/[MITgcm]/MITgcm/eesupp/src/different_multiple.F
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Annotation of /MITgcm/eesupp/src/different_multiple.F

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Revision 1.6 - (hide annotations) (download)
Sat Mar 27 03:51:51 2004 UTC (20 years, 3 months ago) by edhill
Branch: MAIN
CVS Tags: checkpoint57b_post, checkpoint56b_post, checkpoint54d_post, checkpoint54e_post, checkpoint57d_post, checkpoint55, checkpoint54, checkpoint57, checkpoint56, checkpoint53, checkpoint54f_post, checkpoint55i_post, checkpoint55c_post, checkpoint53d_post, checkpoint57a_post, checkpoint54b_post, checkpoint52m_post, checkpoint55g_post, checkpoint57c_post, checkpoint55d_post, checkpoint54a_pre, checkpoint53c_post, checkpoint55d_pre, checkpoint57c_pre, checkpoint55j_post, checkpoint54a_post, checkpoint55h_post, checkpoint57e_post, checkpoint55b_post, checkpoint53a_post, checkpoint55f_post, checkpoint53g_post, eckpoint57e_pre, checkpoint56a_post, checkpoint53f_post, checkpoint57f_pre, checkpoint52n_post, checkpoint53b_pre, checkpoint56c_post, checkpoint57a_pre, checkpoint55a_post, checkpoint53b_post, checkpoint53d_pre, checkpoint55e_post, checkpoint54c_post
Changes since 1.5: +2 -2 lines 
 o cleanup comments (NO CODE CHANGES) in eesupp for protex
 o the "api reference" framework now builds documentation for:
     eesupp, pkg/generic_advdiff, and pkg/gmredi
 o remove mnc from the default gfd in pkg_groups pending
     further testing on systems where NetCDF is not installed
1 edhill 1.6 C $Header: /u/gcmpack/MITgcm/eesupp/src/different_multiple.F,v 1.5 2001/09/21 03:54:34 cnh Exp $
2 cnh 1.5 C $Name: $
3 cnh 1.1 #include "CPP_EEOPTIONS.h"
4    
5 cnh 1.5 CBOP
6     C !ROUTINE: DIFFERENT_MULTIPLE
7    
8     C !INTERFACE:
9 cnh 1.1 LOGICAL FUNCTION DIFFERENT_MULTIPLE( freq, val1, val2 )
10     IMPLICIT NONE
11 cnh 1.5
12     C !DESCRIPTION:
13     C *==========================================================*
14 edhill 1.6 C | LOGICAL FUNCTION DIFFERENT\_MULTIPLE
15 cnh 1.5 C | o Checks two numbers multiple of a third number.
16     C *==========================================================*
17     C | This routine is used for diagnostic and other periodic
18     C | operations. It is very sensitive to arithmetic precision.
19     C | For IEEE conforming arithmetic it works well but for
20     C | cases where short cut arithmetic is used it may not work
21     C | as expected. To overcome this issue compile this routine
22     C | separately with no optimisation.
23     C *==========================================================*
24    
25     C !INPUT PARAMETERS:
26     C == Routine arguments ==
27     C val1, val2 :: Two times that are checked
28     C freq :: Frequency by which times are divided.
29 cnh 1.2 _RL freq, val1, val2
30 cnh 1.5
31     C !LOCAL VARIABLES:
32     C == Local variables ==
33     C f :: Temp. for holding freq
34     C v1, v2, v3, v4 :: Temp. for holding time
35     C d1, d2, d3 :: Temp. for hold difference
36     C step :: Temp. for hold difference used as increment
37 cnh 1.2 _RL f, v1, v2, v3, v4, d1, d2, d3, step
38 cnh 1.5 CEOP
39 cnh 1.2
40     C o Do easy cases first.
41 cnh 1.1 DIFFERENT_MULTIPLE = .FALSE.
42 adcroft 1.3
43     IF ( freq .NE. 0. ) THEN
44     IF ( ABS(val1-val2) .GT. freq ) THEN
45     DIFFERENT_MULTIPLE = .TRUE.
46     ELSE
47    
48     C o This case is more complex because of round-off error
49     f = freq
50     v1 = val1
51     v2 = val2
52     step = v1-v2
53    
54     C Test v1 to see if its a "closest multiple"
55     v3 = v1 + step
56     v4 = NINT(v1/f)*f
57     d1 = v1-v4
58     d2 = v2-v4
59     d3 = v3-v4
60     IF ( ABS(d1) .LE. ABS(d2) .AND. ABS(d1) .LE. ABS(d3) )
61     & DIFFERENT_MULTIPLE = .TRUE.
62    
63     ENDIF ! |val1-val2| > freq
64     ENDIF ! freq != 0
65 cnh 1.1
66 cnh 1.2 END
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