dozer
Structural
- Apr 9, 2001
- 506
Here's a fun one. I have a date routine that among other things it grabs the last two digits of the year from the GETDAT subroutine. Funny thing is when 2005 rolled around it was saying the year is 04!
I fixed the problem, but I was wondering if any of you experts know what going on in the bowels of the computer that would cause this. Here's the code snippet:
SUBROUTINE GET_DATE_TIME(DATE, TIME)
*
* Example of return values:
* DATE = '03/13/01'
* TIME = ' 9:18 am'
*
USE DFLIB
CHARACTER(8) DATE, TIME
CHARACTER(3) AMorPM
INTEGER(2) IYR, IMON, IDAY, IHR, IMIN, ISEC, IHUNDRETHS
*
* GET DATE
*
CALL GETDAT(IYR,IMON,IDAY)
TMP=IYR / 100.0
IYR = (TMP - INT(TMP)) * 100
ENCODE(8,'(I2.2,1H/,I2.2,1H/,I2.2)',DATE)IMON,IDAY,IYR
.
.
.
To fix it I added this to the declarations:
REAL(8) TMP
and I changed
TMP=IYR / 100.0 to TMP = dfloti(IYR) / 100.0
The clue that tipped me off was that I assigned
TMP - INT(TMP) to a variable and looked at it in the debugger. The value was 0.049999 something, something. In our perfect base 10 world it should have been 20.05 - 20 = 0.05.
Yes, I know it's a precision problem, but I want to understand it. Any takers?
I fixed the problem, but I was wondering if any of you experts know what going on in the bowels of the computer that would cause this. Here's the code snippet:
SUBROUTINE GET_DATE_TIME(DATE, TIME)
*
* Example of return values:
* DATE = '03/13/01'
* TIME = ' 9:18 am'
*
USE DFLIB
CHARACTER(8) DATE, TIME
CHARACTER(3) AMorPM
INTEGER(2) IYR, IMON, IDAY, IHR, IMIN, ISEC, IHUNDRETHS
*
* GET DATE
*
CALL GETDAT(IYR,IMON,IDAY)
TMP=IYR / 100.0
IYR = (TMP - INT(TMP)) * 100
ENCODE(8,'(I2.2,1H/,I2.2,1H/,I2.2)',DATE)IMON,IDAY,IYR
.
.
.
To fix it I added this to the declarations:
REAL(8) TMP
and I changed
TMP=IYR / 100.0 to TMP = dfloti(IYR) / 100.0
The clue that tipped me off was that I assigned
TMP - INT(TMP) to a variable and looked at it in the debugger. The value was 0.049999 something, something. In our perfect base 10 world it should have been 20.05 - 20 = 0.05.
Yes, I know it's a precision problem, but I want to understand it. Any takers?
