When I have to use for/next for processing arrays,
I like, I suspect many others, tend to put the array ubound into a local
variable like so:
Dim counter as integer = myarray.ubound // ( new rb syntax )
For I as integer = 0 to counter
...
Next
As opposed to , what would be more clean:
For I as integer = 0 to myarray.ubound
...
Next
Now I just did some timings, and it seems that there is a slight ( not great
) performance advantage with using a local variable. I used the following
code ( with an empty array )
//-------
dim u as integer = UBound(arr)
Result.Text = "Started"
app.DoEvents
for j as integer = 0 to 200000000
for i as integer = 0 to u
Next
Next
Beep
Result.Text= "FINISHED"
//--------
and:
// -------
Result.Text = "Started"
app.DoEvents
for j as integer = 0 to 200000000
for i as integer = 0 to UBound(arr)
Next
Next
Beep
Result.Text= "FINISHED"
//--------
This makes me wonder: - Idoes Ubound use a method/function call to get the
ubound value, or does the RB generate code to directly access a "property"
or variable holding the internal array size ?.
Naturally there would be some speed advantage to NOT using any function to
get the size.
Basically I would prefer not to have to use the local variable counter
method, or as I often have done - creating a class property to hold the
array count. It would be so much cleaner just to use UBOUND directly in the
for loop, knowing that I incur no performance penalty for doing so.
Anyone have info on this ? My test seems to suggest there is not a huge
difference in speed, but a difference nevertheless.
Regards,
Dan
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