Runtime script with inexplicable results...

I have a function in my scripts to calculate the runtime in seconds for a program, using the Timer value from windows, which returns the current time as seconds from midnight.

The blue code is my script run at the beginning of a part program. The red code is what is run at the end. (I've cut and pasted these sections from the scripts...they are too long.) In the event that a program runs through midnight, I have a section in the red code to correctly calculate runtime. I've tested this code in the excel editor while resetting my computer clock to 11:59 PM and running it through midnight, and it works. Unfortunately, this code does not work when running PC-DMIS through midnight. I get program times of more than 86400.

Any ideas why this is not calculating correctly only when run through PC-DMIS?

[COLOR="Blue"]Sub Main()

Dim BeforeTime As String
BeforeTime = Timer
BeforeTime = CLng(BeforeTime)

End Sub[/COLOR]

[COLOR="Red"]
Sub Main()

Dim Aftertime As String
Aftertime = Timer
Aftertime = CLng(Aftertime)
Dim RunTime As String

If Aftertime < BeforeTime Then
RunTime = (86400 - BeforeTime) + Aftertime
Else
RunTime = Aftertime - BeforeTime
End If

End Sub[/COLOR]

mbwolfe over 14 years ago
I have a function in my scripts to calculate the runtime in seconds for a program, using the Timer value from windows, which returns the current time as seconds from midnight.

The blue code is my script run at the beginning of a part program. The red code is what is run at the end. (I've cut and pasted these sections from the scripts...they are too long.) In the event that a program runs through midnight, I have a section in the red code to correctly calculate runtime. I've tested this code in the excel editor while resetting my computer clock to 11:59 PM and running it through midnight, and it works. Unfortunately, this code does not work when running PC-DMIS through midnight. I get program times of more than 86400.

Any ideas why this is not calculating correctly only when run through PC-DMIS?

[COLOR="Blue"]Sub Main() Dim BeforeTime As String BeforeTime = Timer BeforeTime = CLng(BeforeTime) End Sub[/COLOR] [COLOR="Red"] Sub Main() Dim Aftertime As String Aftertime = Timer Aftertime = CLng(Aftertime) Dim RunTime As String If Aftertime < BeforeTime Then RunTime = (86400 - BeforeTime) + Aftertime Else RunTime = Aftertime - BeforeTime End If End Sub[/COLOR]

There are lots of problems with your design here. I know because I've made this type of mistake before.

You're assuming that you're off by 1 day (which is probably OK for this), but won't work when you reuse this (and you will, trust me).

Better would be:

while AfterTime < BeforeTIme
BeforeTIme = BeforeTime - 86400

which would correct for any number of days off. This is easier to express with:
BeforeTime = BeforeTIme Mod 86400

But that is really unnecessary as well. More to the point, you're getting into a lot of assumptions about the underlying structure of the data, and I suspect that's causing you the problem. So do this instead:

BeforeTime = Now
...
AfterTime = Now
RunTime = DateDiff (s, AfterTIme, BeforeTIme)

and let the language do the thinking for you

If you're REALLY interested, read Eric Lippert's blog about how he fixed this particular function (he's a software engineer at Microsoft) to see just what you're assuming about:
http://blogs.msdn.com/b/ericlippert/archive/2003/09/16/53013.aspx

Hope this helps.
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Chally72 over 14 years ago

Thanks for the information. Eric's blog and the Spolsky article within made for interesting reading.

When learning on your own, you just don't know what you don't know. I will update this thread when I get the code changed over.
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