Normal vs. Stringbuilder Concatenation; unusual tick numbers

[MattC231]

StringBuilder.zip

This is the objective of my assignment:
"This exercise explores the merits of using Stringbuilder to perform string manipulations, in particular, concatenations. Strings are reference objects and immutable. Modifications To a string of any kind require that a new string be created, and that the revised contents of the old string be copied to the location of the new string. As you can imagine, this process can quickly become very costly in terms of resources. The solution is to use StringBuilder, which allocates a buffer instead, and makes the changes in place. StringBuilder is not a string but rather a workspace. The internal string is easily extracted from StringBuilder buffer using the ToString()method."

When I execute the app, I get a number of ticks for normal string concatenation but, string builder concatenation, I get 0 ticks and for difference, I get infinite ticks. When I repeatedly click the go button, I eventually get a number for stringbuilder concatenation and difference, but once I click it again, I get 0 and infinite again. Repeat that and same results.

This code was given by the professor. Can you tell me if its intentional or if there's a problem with the code? If so, how can I fix it?

[.paul.]

Can you post the code?
The StringBuilder would be quicker, and depending on how much you're using it, it could be very fast...

[MattC231]

Public Class frmStringBuilder

    Private Sub btnGo_Click(sender As Object, e As EventArgs) Handles btnGo.Click

        Dim str As String
        Dim strAll As String
        Dim sb As New System.Text.StringBuilder
        Dim intIterations As Integer = CInt(updIterations.Value)
        Dim intCtr As Integer
        Dim lngStart, lngFinish As Long
        Dim lngDiff1, lngDiff2 As Long

        lblNormal.Text = ""
        lblStringBuilder.Text = ""
        lblDifference.Text = ""
        Me.Cursor = Cursors.WaitCursor
        strAll = String.Empty

        '* Normal Concatenation
        str = txtString.Text & " "
        lngStart = Now.Ticks

        For intCtr = 0 To intIterations
            strAll = strAll & str
        Next

        lngFinish = Now.Ticks
        lngDiff1 = (lngFinish - lngStart)
        lblNormal.Text = lngDiff1.ToString("N0") & " ticks"
        Debug.WriteLine(strAll.Length.ToString())
        sb.EnsureCapacity(intIterations * txtString.Text.Length)

        '* Stringbuilder Concatenation
        lngStart = Now.Ticks

        For intCtr = 0 To intIterations
            sb.Append(str)
        Next

        lngFinish = Now.Ticks
        lngDiff2 = (lngFinish - lngStart)
        lblStringBuilder.Text = lngDiff2.ToString("N0") & " ticks"
        Debug.WriteLine(sb.ToString.Length.ToString())

        '* Difference
        lblDifference.Text = String.Format("{0:N0}", lngDiff1 / lngDiff2) & " times"
        sb = Nothing
        Me.Cursor = Cursors.Default

    End Sub

End Class

[.paul.]

What sort of number of iterations are we talking about? try it with 100,000

[MattC231]

Ok, 100,000 gives results, but 10,000 give 0 and infinite

[.paul.]

What happens if you run it for 10,000 iterations, then display the contents of the stringbuilder into a textbox?
If it's what it should be, everything must be working ok, so report your findings to your teacher. I did notice you're setting the size of the stringbuilder before any iterations occur. That would reduce the time taken to add the strings significantly.

[MattC231]

ok, thanks

[Sitten Spynne]

Today's computers are so fast you cannot measure the time it takes to do one operation. A tick is some fraction of a second, and your CPU cycles are fractions of Ticks. So the time it takes to do most operations is less than a single Tick, which means 0 in most cases.

So when you're benchmarking things, it's best to execute them for hundreds of thousands or millions of iterations, so all of the fractions of a tick can add up to whole ticks. Also: DateTime.Now is not a high-precision clock. Read the documentation for System.Diagnostics.Stopwatch. That is a much more high-precision clock intended to be used for measuring the performance of algorithms.

[MattC231]

Thanks for the explanation

[.paul.]

If that's the performance testing code you've been given, i'd mention it's not the most efficient code for measuring time taken to complete a set of iterations.
In addition to the StopWatch class, i generally use Environment.TickCount

https://msdn.microsoft.com/en-us/lib...or=-2147217396

[MattC231]

Ok, yeah, that looks interesting.