Iteration performance issue
 

Hi,
I am trying to programmatically iterate through rows, picking the values of
two cells per row, doing some (simple arithmetic) calculations and writing
output to another sheet. (One write per 32 reads in average.)

I can't figure out what I am doing wrong, because it takes some awful lot of
time. My input worksheet has 31000 rows and it takes some 40min to step
through them. I am using
Worksheet.Cells(y, x) syntax to retrieve and write values from/to cells.
Can't believe Excel is so lame, hope a faster syntax exists. Even Access
steps through a recordset faster than this. Could not find anything relevant
in Help. Range transfer to/from VBA array would be great. Using Excel XP
2002 on a 1.5GHz Pent with 512M RAM.

Thanks in advance!

Iteration performance issue
 

Can't do much if you don't post your code.

one can hardly program to paragraph 1.

However, it sounds like you could put a formula in the destination sheet and
drag fill it down the column to do what you want.

--
Regards,
Tom Ogilvy

"J.Smith" wrote in message
...
Hi,
I am trying to programmatically iterate through rows, picking the values
of
two cells per row, doing some (simple arithmetic) calculations and writing
output to another sheet. (One write per 32 reads in average.)

I can't figure out what I am doing wrong, because it takes some awful lot
of
time. My input worksheet has 31000 rows and it takes some 40min to step
through them. I am using
Worksheet.Cells(y, x) syntax to retrieve and write values from/to cells.
Can't believe Excel is so lame, hope a faster syntax exists. Even Access
steps through a recordset faster than this. Could not find anything
relevant
in Help. Range transfer to/from VBA array would be great. Using Excel XP
2002 on a 1.5GHz Pent with 512M RAM.

Thanks in advance!

Iteration performance issue
 

Range transfer to/from VBA array would be great.


This method is reasonably fast

Sub klhjok()
Dim vArr As Variant

application.screenupdating=False
application.calculation=xlManual
'
' get range into variant containing array
'
vArr = Worksheets("fred").Range("A3:L50")
'
' show an element in the arry
'
MsgBox vArr(10, 10)
'
' change element in array
'
vArr(10, 10) = 123456
'
' put array back to sheet
' in different place
'
Worksheets("fred").Range("A3:L50").Offset(3, 20) = vArr
application.screenupdating=true
application.calculation=xlAutomatic

End Sub

regards
Charles
______________________
Decision Models
The Excel Calculation Site.
www.DecisionModels.com

Iteration performance issue
 

vArr = Worksheets("fred").Range("A3:L50")
Worksheets("fred").Range("A3:L50").Offset(3, 20) = vArr

Oh, THAT's how you get a range into/out of an array? Great!
Didn't know that.

application.calculation=xlAutomatic
Wasn't aware of that, either.

I will definitely try these two methods to speed up the code.

(Screenupdating has already been taken care of).

Thanks a lot, Charles!

Iteration performance issue
 

The "application.calculation=xlManual" did the trick!
There was even no need to deal with an array - the same
13K rows got processed in 11sec (as oppsed to 40 min),
which is fine by me.

I think I got an idea where the problem was.
My input sheet with 13K rows has 3 columns with "cascading" formulae
(the next row takes it's input from the previous one)
which apparently got recalculated each time values got written to
the output sheet. (I found it out by removing the
"writing code" and running it with autoCalc enabled - the
result was about as quick as the complete code with autoCalc disabled).

The funny thing is that the cells I was
writing to were NOT used as inputs by any formula.
Why would Excel recalculate them?
(It's more of a rhetorical question.)

Many thanks again, Charles!
J.Smith


"Charles Williams" wrote in message
...
Range transfer to/from VBA array would be great.


This method is reasonably fast

Sub klhjok()
Dim vArr As Variant

application.screenupdating=False
application.calculation=xlManual
'
' get range into variant containing array
'
vArr = Worksheets("fred").Range("A3:L50")
'
' show an element in the arry
'
MsgBox vArr(10, 10)
'
' change element in array
'
vArr(10, 10) = 123456
'
' put array back to sheet
' in different place
'
Worksheets("fred").Range("A3:L50").Offset(3, 20) = vArr
application.screenupdating=true
application.calculation=xlAutomatic

End Sub

regards
Charles
______________________
Decision Models
The Excel Calculation Site.
www.DecisionModels.com