Optimization

[sebs]

Hey,

I am running a large loop and so far I cut down a lot of the processing by optimizing little things that made a huge difference.

But I need to know some more, which between the two will take less time/memory:

Dim perc As Long
 
For x = 0 To 50000
  perc = Round((x / 50000) * 100)
  fraProgress.Caption = "Progress - " & perc & "%"
Next

or

For x = 0 To 50000
  fraProgress.Caption = "Progress - " & Round((x / 50000) * 100) & "%"
Next

I am thinking the first one would be the best, the second VB will create a Variant for to calculate, right ?

Thanks

[Hack]

I would go with the first one.

[trisuglow]

Would it be better to replace "(x/50000) * 100" with "x/500"?

[sebs]

Would it be better to replace "(x/50000) * 100" with "x/500"?

Hmmm, I had replaced my variable that hold the number with 50000, but I guess if I would create another variable that hold myNumber / 100, then I could do:

x / myNewVariable

Interesting, I will try that right away.

[sebs]

It works, not much difference, but I am sure there's one.

Here's my code now:

Dim numOfBooks As Long, numOfBooksDivided As Long
 
numOfBooks = UBound(allBooks, 2)
numOfBooksDivided = numOfBooks / 100
 
For x = 0 To numOfBooks
    perc = Round( (x + 1) / numOfBooksDivided )
    fraProgress.Caption = "Progress - " & perc & "%"
Next

[eyeRmonkey]

If you want to speed it up (and don't care about decimal precision) try this:

perc = (x + 1) \ numOfBooksDivided

That is integer division. I might not be what you want because you could lose some accuracy.

[sebs]

If you want to speed it up (and don't care about decimal precision) try this:

perc = (x + 1) \ numOfBooksDivided

That is integer division. I might not be what you want because you could lose some accuracy.

Well I rounded it off anyway, so thanks, it works for this purpose.

[Merri]

Uhhuh, with my test the code doesn't even run. The code wouldn't work with less than a hundred books, because you get a divizion by zero error. This is because you use Long datatype instead of Single or Double, which can hold decimals.

Now, to actually make things fast and smooth:

Private Sub Form_Load()
    Dim numOfBooks As Long, numOfBooksDivided As Double
    Dim perc As Double
    ' then some test code...
    Dim allBooks() As Long, x As Long
    ReDim allBooks(2, 20)
    
    numOfBooks = UBound(allBooks, 2)
    numOfBooksDivided = 100 / numOfBooks
    
    For x = 0 To numOfBooks
        Me.Caption = "Progress - " & CStr(CLng(perc)) & "%"
        perc = perc + numOfBooksDivided
    Next
End Sub

Boy am I efficient there!

[sebs]

Hehe, that is because I did not include all my code, the allBooks are a returned of recordset, so let say

Dim allBooks() As Variant
ReDim allBooks(2, 50000)

And I do not need decimal, your code show 1.23232323123123%, which is not what I need, I do not need decimal. But I like you idea though

[Merri]

Did you include the CStr(CLng()) conversions? It first converts to Long and then to String (avoiding automatical datatype coercion, which causes slowdown). A Long datatype can't hold a decimal.

[sebs]

Did you include the CStr(CLng()) conversions? It first converts to Long and then to String (avoiding automatical datatype coercion, which causes slowdown). A Long datatype can't hold a decimal.

No, but but wouldn't two conversion take longer than just perc = (x + 1) \ numOfBooksDivided ?

[Merri]

The other conversion would be made automatically through datatype coercion if it wasn't there (being slightly slower). I admit using Double datatype is slower than a Long (which is the fastest with 32-bit processor), but if we really take a closer look into your code, you are using Strings, which cause far more slowdown than anything else in the code. So the only advantage to my code is that it is less error prone (no divizion by zero errors, unless there is only one book; but that is easy to check for), it is far more accurate with lesser book amounts and it is still very lightweight (only two mathematical calculations per loop and a conversion for progress display).


So, the next step to increase performance would be to make the label update only if it is changed:

Dim perclast As Long
 
    ' ... the other code...
 
    ' a small trick to make the "0%" appear
    perclast = -1
    For x = 0 To numOfBooks
        If perclast < CLng(perc) Then
            perclast = CLng(perc)
            Me.Caption = "Progress - " & CStr(perclast) & "%"
        End If
        perc = perc + numOfBooksDivided
    Next

And now label is updated only if it required (= 101 times instead of 50000 times).

[sebs]

Yeah, the label update makes a lot of sense, thanks.

It made me think of another thing I was doing wrong, I also have a progress bar and I was setting the max to the numOfBooks and was incrementing it 50000 times, instead I set the max to 100 and will increment with perc only if it changed

Thanks again.

[moeur]

I used the high-resolution performance counter to time these methods. The fastest method at 61ms is

'*** 61ms
Dim numOfBooks As Long, numOfBooksDivided As Long
Dim perc As Long
 
numOfBooks = UBound(allBooks, 2)
numOfBooksDivided = numOfBooks / 100
 
For x = 0 To numOfBooks
    'Don't use this one, it takes 90ms
    'perc = Round((x + 1) / numOfBooksDivided)
    perc = (x + 1) \ numOfBooksDivided
    fraProgress.Caption = "Progress - " & perc & "%"
Next

The next method took 74ms

'*** 74ms
Dim numOfBooks As Long, numOfBooksDivided As Double
    Dim perc As Double
 
    numOfBooks = UBound(allBooks, 2)
    numOfBooksDivided = 100 / numOfBooks
 
    For x = 0 To numOfBooks
        fraProgress.Caption = "Progress - " & CStr(CLng(perc)) & "%"
        perc = perc + numOfBooksDivided
    Next

Here is a post on how to use the high-resolution performance counter
http://www.vbforums.com/showthread.p...18#post2033918