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C $Header: /u/gcmpack/MITgcm/eesupp/src/different_multiple.F,v 1.9 2005/09/27 18:38:28 jmc Exp $ |
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C $Name: $ |
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|
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#include "CPP_EEOPTIONS.h" |
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|
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CBOP |
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C !ROUTINE: DIFFERENT_MULTIPLE |
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|
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C !INTERFACE: |
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LOGICAL FUNCTION DIFFERENT_MULTIPLE( freq, val1, step ) |
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IMPLICIT NONE |
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|
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C !DESCRIPTION: |
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C *==========================================================* |
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C | LOGICAL FUNCTION DIFFERENT\_MULTIPLE |
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C | o Checks if a multiple of freq exist |
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C | around val1 +/- step/2 |
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C *==========================================================* |
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C | This routine is used for diagnostic and other periodic |
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C | operations. It is very sensitive to arithmetic precision. |
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C | For IEEE conforming arithmetic it works well but for |
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C | cases where short cut arithmetic is used it may not work |
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C | as expected. To overcome this issue compile this routine |
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C | separately with no optimisation. |
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C *==========================================================* |
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|
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C !INPUT PARAMETERS: |
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C == Routine arguments == |
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C freq :: Frequency by which time is divided. |
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C val1 :: time that is checked |
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C step :: length of time interval (around val1) that is checked |
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_RL freq, val1, step |
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|
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C---+----1----+----2----+----3----+----4----+----5----+----6----+----7-|--+----| |
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|
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C !LOCAL VARIABLES: |
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C == Local variables == |
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C v1, v2, v3, v4 :: Temp. for holding time |
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C d1, d2, d3 :: Temp. for hold difference |
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_RL v1, v2, v3, v4, d1, d2, d3 |
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CEOP |
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|
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C o Do easy cases first. |
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DIFFERENT_MULTIPLE = .FALSE. |
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|
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IF ( freq .NE. 0. ) THEN |
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IF ( ABS(step) .GT. freq ) THEN |
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DIFFERENT_MULTIPLE = .TRUE. |
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ELSE |
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|
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C o This case is more complex because of round-off error |
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v1 = val1 |
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v2 = val1 - step |
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v3 = val1 + step |
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|
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C Test v1 to see if its a "closest multiple" |
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v4 = NINT(v1/freq)*freq |
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d1 = v1-v4 |
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d2 = v2-v4 |
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d3 = v3-v4 |
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IF ( ABS(d1) .LT. ABS(d2) .AND. ABS(d1) .LE. ABS(d3) ) |
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& DIFFERENT_MULTIPLE = .TRUE. |
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|
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ENDIF |
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ENDIF |
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|
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RETURN |
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END |
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|
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CBOP |
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C !ROUTINE: DIFFERENT_MULTIPLE |
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|
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C !INTERFACE: |
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subroutine ad_s_DIFFERENT_MULTIPLE( freq, val1, step, isit ) |
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IMPLICIT NONE |
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|
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C !DESCRIPTION: |
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C *==========================================================* |
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C | LOGICAL FUNCTION DIFFERENT\_MULTIPLE |
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C | o Checks if a multiple of freq exist |
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C | around val1 +/- step/2 |
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C *==========================================================* |
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C | This routine is used for diagnostic and other periodic |
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C | operations. It is very sensitive to arithmetic precision. |
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C | For IEEE conforming arithmetic it works well but for |
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C | cases where short cut arithmetic is used it may not work |
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C | as expected. To overcome this issue compile this routine |
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C | separately with no optimisation. |
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C *==========================================================* |
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|
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C !INPUT PARAMETERS: |
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C == Routine arguments == |
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C freq :: Frequency by which time is divided. |
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C val1 :: time that is checked |
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C step :: length of time interval (around val1) that is checked |
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_RL freq, val1, step |
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logical isit |
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|
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C---+----1----+----2----+----3----+----4----+----5----+----6----+----7-|--+----| |
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|
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C !LOCAL VARIABLES: |
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C == Local variables == |
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C v1, v2, v3, v4 :: Temp. for holding time |
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C d1, d2, d3 :: Temp. for hold difference |
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_RL v1, v2, v3, v4, d1, d2, d3 |
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CEOP |
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|
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C o Do easy cases first. |
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isit = .FALSE. |
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|
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IF ( freq .NE. 0. ) THEN |
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IF ( ABS(step) .GT. freq ) THEN |
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isit = .TRUE. |
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ELSE |
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|
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C o This case is more complex because of round-off error |
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v1 = val1 |
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v2 = val1 - step |
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v3 = val1 + step |
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|
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C Test v1 to see if its a "closest multiple" |
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v4 = NINT(v1/freq)*freq |
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d1 = v1-v4 |
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d2 = v2-v4 |
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d3 = v3-v4 |
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IF ( ABS(d1) .LT. ABS(d2) .AND. ABS(d1) .LE. ABS(d3) ) |
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& isit = .TRUE. |
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|
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ENDIF |
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ENDIF |
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|
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RETURN |
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END |
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