pkg/openad/ad_s_different_multiple.F

#include "CPP_EEOPTIONS.h"
CBOP
C     !ROUTINE: DIFFERENT_MULTIPLE

C     !INTERFACE:
      subroutine oad_s_DIFFERENT_MULTIPLE( freq, val1, step, isit )
      IMPLICIT NONE

C     !DESCRIPTION:
C     *==========================================================*
C     | LOGICAL FUNCTION DIFFERENT\_MULTIPLE                       
C     | o Checks if a multiple of freq exist
C     |   around val1 +/- step/2
C     *==========================================================*
C     | This routine is used for diagnostic and other periodic    
C     | operations. It is very sensitive to arithmetic precision. 
C     | For IEEE conforming arithmetic it works well but for      
C     | cases where short cut arithmetic  is used it may not work 
C     | as expected. To overcome this issue compile this routine  
C     | separately with no optimisation.                          
C     *==========================================================*

C     !INPUT PARAMETERS:
C     == Routine arguments ==
C     freq       :: Frequency by which time is divided.
C     val1       :: time that is checked 
C     step       :: length of time interval (around val1) that is checked 
      _RL  freq, val1, step
      logical isit

C---+----1----+----2----+----3----+----4----+----5----+----6----+----7-|--+----|

C     !LOCAL VARIABLES:
C     == Local variables ==
C     v1, v2, v3, v4 :: Temp. for holding time
C     d1, d2, d3     :: Temp. for hold difference
      _RL  v1, v2, v3, v4, d1, d2, d3
CEOP

C     o Do easy cases first.
      isit = .FALSE.

      IF ( freq .NE. 0. ) THEN
        IF ( ABS(step) .GT. freq ) THEN
         isit = .TRUE.
        ELSE

C         o This case is more complex because of round-off error
          v1 = val1
          v2 = val1 - step
          v3 = val1 + step

C         Test v1 to see if its a "closest multiple"
          v4 = NINT(v1/freq)*freq
          d1 = v1-v4
          d2 = v2-v4
          d3 = v3-v4
          IF ( ABS(d1) .LT. ABS(d2) .AND. ABS(d1) .LE. ABS(d3) )
     &        isit = .TRUE.

        ENDIF
      ENDIF

      RETURN
      END
1	#include "CPP_EEOPTIONS.h"
2	CBOP
3	C !ROUTINE: DIFFERENT_MULTIPLE
4
5	C !INTERFACE:
6	subroutine oad_s_DIFFERENT_MULTIPLE( freq, val1, step, isit )
7	IMPLICIT NONE
8
9	C !DESCRIPTION:
10	C ==========================================================
11	C \| LOGICAL FUNCTION DIFFERENT\_MULTIPLE
12	C \| o Checks if a multiple of freq exist
13	C \| around val1 +/- step/2
14	C ==========================================================
15	C \| This routine is used for diagnostic and other periodic
16	C \| operations. It is very sensitive to arithmetic precision.
17	C \| For IEEE conforming arithmetic it works well but for
18	C \| cases where short cut arithmetic is used it may not work
19	C \| as expected. To overcome this issue compile this routine
20	C \| separately with no optimisation.
21	C ==========================================================
22
23	C !INPUT PARAMETERS:
24	C == Routine arguments ==
25	C freq :: Frequency by which time is divided.
26	C val1 :: time that is checked
27	C step :: length of time interval (around val1) that is checked
28	_RL freq, val1, step
29	logical isit
30
31	C---+----1----+----2----+----3----+----4----+----5----+----6----+----7-\|--+----\|
32
33	C !LOCAL VARIABLES:
34	C == Local variables ==
35	C v1, v2, v3, v4 :: Temp. for holding time
36	C d1, d2, d3 :: Temp. for hold difference
37	_RL v1, v2, v3, v4, d1, d2, d3
38	CEOP
39
40	C o Do easy cases first.
41	isit = .FALSE.
42
43	IF ( freq .NE. 0. ) THEN
44	IF ( ABS(step) .GT. freq ) THEN
45	isit = .TRUE.
46	ELSE
47
48	C o This case is more complex because of round-off error
49	v1 = val1
50	v2 = val1 - step
51	v3 = val1 + step
52
53	C Test v1 to see if its a "closest multiple"
54	v4 = NINT(v1/freq)*freq
55	d1 = v1-v4
56	d2 = v2-v4
57	d3 = v3-v4
58	IF ( ABS(d1) .LT. ABS(d2) .AND. ABS(d1) .LE. ABS(d3) )
59	& isit = .TRUE.
60
61	ENDIF
62	ENDIF
63
64	RETURN
65	END