| 1 |
C $Header: /u/gcmpack/models/MITgcmUV/eesupp/src/different_multiple.F,v 1.2 1998/11/03 15:28:03 cnh Exp $ |
| 2 |
#include "CPP_EEOPTIONS.h" |
| 3 |
|
| 4 |
CStartofinterface |
| 5 |
LOGICAL FUNCTION DIFFERENT_MULTIPLE( freq, val1, val2 ) |
| 6 |
C /==========================================================\ |
| 7 |
C | LOGICAL FUNCTION DIFFERENT_MULTIPLE | |
| 8 |
C | o Checks two numbers multiple of a third number. | |
| 9 |
C |==========================================================| |
| 10 |
C | This routine is used for diagnostic and other periodic | |
| 11 |
C | operations. It is very sensitive to arithmetic precision.| |
| 12 |
C | For IEEE conforming arithmetic is works well but for | |
| 13 |
C | cases where short cut arithmetic is used it may not work| |
| 14 |
C | as expected. To overcome this issue compile this routine | |
| 15 |
C | separately with no optimisation. | |
| 16 |
C \==========================================================/ |
| 17 |
IMPLICIT NONE |
| 18 |
C Returns TRUE if val1 and val2 are different multiples of freq. |
| 19 |
_RL freq, val1, val2 |
| 20 |
CEndofinterface |
| 21 |
_RL f, v1, v2, v3, v4, d1, d2, d3, step |
| 22 |
|
| 23 |
C o Do easy cases first. |
| 24 |
DIFFERENT_MULTIPLE = .FALSE. |
| 25 |
|
| 26 |
IF ( freq .NE. 0. ) THEN |
| 27 |
IF ( ABS(val1-val2) .GT. freq ) THEN |
| 28 |
DIFFERENT_MULTIPLE = .TRUE. |
| 29 |
ELSE |
| 30 |
|
| 31 |
C o This case is more complex because of round-off error |
| 32 |
f = freq |
| 33 |
v1 = val1 |
| 34 |
v2 = val2 |
| 35 |
step = v1-v2 |
| 36 |
|
| 37 |
C Test v1 to see if its a "closest multiple" |
| 38 |
v3 = v1 + step |
| 39 |
v4 = NINT(v1/f)*f |
| 40 |
d1 = v1-v4 |
| 41 |
d2 = v2-v4 |
| 42 |
d3 = v3-v4 |
| 43 |
IF ( ABS(d1) .LE. ABS(d2) .AND. ABS(d1) .LE. ABS(d3) ) |
| 44 |
& DIFFERENT_MULTIPLE = .TRUE. |
| 45 |
|
| 46 |
ENDIF ! |val1-val2| > freq |
| 47 |
ENDIF ! freq != 0 |
| 48 |
|
| 49 |
END |
Parent Directory
| 
Revision Log
| 
Revision Graph