StringBuilder performance

JC Voon

Hi all:

If i'm not wrong, StringBuilder should faster than string concat using
&.
But the following code:

1:
Dim s as string
For i As Integer = 1 To 1000000
s = "11111111111111111111111111111111" & _
"11111111111111111111111111111111" & _
"11111111111111111111111111111111" & _
"11111111111111111111111111111111" & _
"11111111111111111111111111111111" & _
"11111111111111111111111111111111" & _
"11111111111111111111111111111111" & _
"11111111111111111111111111111111" & _
"11111111111111111111111111111111" & _
"11111111111111111111111111111111" & _
"11111111111111111111111111111111" & _
"11111111111111111111111111111111" & _
"11111111111111111111111111111111" & _
"11111111111111111111111111111111" & _
"11111111111111111111111111111111" & _
"11111111111111111111111111111111" & _
"11111111111111111111111111111111" & _
"11111111111111111111111111111111" & _
"11111111111111111111111111111111" & _
"11111111111111111111111111111111"
Next

2:
Dim sb As StringBuilder = New StringBuilder
For i As Integer = 1 To 1000000
sb.Append("11111111111111111111111111111111")
sb.Append("11111111111111111111111111111111")
sb.Append("11111111111111111111111111111111")
sb.Append("11111111111111111111111111111111")
sb.Append("11111111111111111111111111111111")
sb.Append("11111111111111111111111111111111")
sb.Append("11111111111111111111111111111111")
sb.Append("11111111111111111111111111111111")
sb.Append("11111111111111111111111111111111")
sb.Append("11111111111111111111111111111111")
sb.Append("11111111111111111111111111111111")
sb.Append("11111111111111111111111111111111")
sb.Append("11111111111111111111111111111111")
sb.Append("11111111111111111111111111111111")
sb.Append("11111111111111111111111111111111")
sb.Append("11111111111111111111111111111111")
sb.Append("11111111111111111111111111111111")
sb.Append("11111111111111111111111111111111")
sb.Append("11111111111111111111111111111111")
sb.Append("11111111111111111111111111111111")
Next

Why stringbuiler is slower ?

Thanks
JCVoon

Nov 21 '05 #1

Subscribe Post Reply

1204

Robin Tucker

Probably because the optimiser concatenates the string at "compile" time and
is just assigning it at run-time (if even that). If you tried that with
variable strings, you'll probably find it's slower.

"JC Voon" <jc*******@yahoo.com> wrote in message
news:42***************@msnews.microsoft.com...

Hi all:

If i'm not wrong, StringBuilder should faster than string concat using
&.
But the following code:

1:
Dim s as string
For i As Integer = 1 To 1000000
s = "11111111111111111111111111111111" & _
"11111111111111111111111111111111" & _
"11111111111111111111111111111111" & _
"11111111111111111111111111111111" & _
"11111111111111111111111111111111" & _
"11111111111111111111111111111111" & _
"11111111111111111111111111111111" & _
"11111111111111111111111111111111" & _
"11111111111111111111111111111111" & _
"11111111111111111111111111111111" & _
"11111111111111111111111111111111" & _
"11111111111111111111111111111111" & _
"11111111111111111111111111111111" & _
"11111111111111111111111111111111" & _
"11111111111111111111111111111111" & _
"11111111111111111111111111111111" & _
"11111111111111111111111111111111" & _
"11111111111111111111111111111111" & _
"11111111111111111111111111111111" & _
"11111111111111111111111111111111"
Next

2:
Dim sb As StringBuilder = New StringBuilder
For i As Integer = 1 To 1000000
sb.Append("11111111111111111111111111111111")
sb.Append("11111111111111111111111111111111")
sb.Append("11111111111111111111111111111111")
sb.Append("11111111111111111111111111111111")
sb.Append("11111111111111111111111111111111")
sb.Append("11111111111111111111111111111111")
sb.Append("11111111111111111111111111111111")
sb.Append("11111111111111111111111111111111")
sb.Append("11111111111111111111111111111111")
sb.Append("11111111111111111111111111111111")
sb.Append("11111111111111111111111111111111")
sb.Append("11111111111111111111111111111111")
sb.Append("11111111111111111111111111111111")
sb.Append("11111111111111111111111111111111")
sb.Append("11111111111111111111111111111111")
sb.Append("11111111111111111111111111111111")
sb.Append("11111111111111111111111111111111")
sb.Append("11111111111111111111111111111111")
sb.Append("11111111111111111111111111111111")
sb.Append("11111111111111111111111111111111")
Next

Why stringbuiler is slower ?

Thanks
JCVoon

Nov 21 '05 #2

Herfried K. Wagner [MVP]

"JC Voon" <jc*******@yahoo.com> schrieb:

If i'm not wrong, StringBuilder should faster than string concat using
&.
But the following code:

1:
Dim s as string
For i As Integer = 1 To 1000000
s = "11111111111111111111111111111111" & _
"11111111111111111111111111111111" & _
"11111111111111111111111111111111" & _
"11111111111111111111111111111111" & _
"11111111111111111111111111111111" & _
"11111111111111111111111111111111" & _
"11111111111111111111111111111111" & _
"11111111111111111111111111111111" & _
"11111111111111111111111111111111" & _
"11111111111111111111111111111111" & _
"11111111111111111111111111111111" & _
"11111111111111111111111111111111" & _
"11111111111111111111111111111111" & _
"11111111111111111111111111111111" & _
"11111111111111111111111111111111" & _
"11111111111111111111111111111111" & _
"11111111111111111111111111111111" & _
"11111111111111111111111111111111" & _
"11111111111111111111111111111111" & _
"11111111111111111111111111111111"
Next

['StringBuilder' sample]
Why stringbuiler is slower ?

In this particular case, the compiler will find out that the text you are
assigning to 's' is a single constant string, and thus the compiler will
emit a single string literal. Consequently no concatenations are performed
at tuntime. Note that this is only the case when concatenating constant
strings.

--
M S Herfried K. Wagner
M V P <URL:http://dotnet.mvps.org/>
V B <URL:http://classicvb.org/petition/>

Nov 21 '05 #3

Chris Dunaway

You're not concatenating anything. The compiler recognizes your string
s as a constant and does all the concatenating once at compile time.
If you look at the IL that is emitted, you will see this.

Nov 21 '05 #4

JC Voon

Hi:

Thanks for the reply.
After modify my code, i can see the different.

Dim tStart As Double

Dim sb As StringBuilder = New StringBuilder
tStart = DateAndTime.Timer
For i As Integer = 1 To 5000
sb.Append("11111111111111111111111111111111")
sb.Append("11111111111111111111111111111111")
sb.Append("11111111111111111111111111111111")
sb.Append("11111111111111111111111111111111")
sb.Append("11111111111111111111111111111111")
sb.Append("11111111111111111111111111111111")
sb.Append("11111111111111111111111111111111")
sb.Append("11111111111111111111111111111111")
sb.Append("11111111111111111111111111111111")
sb.Append("11111111111111111111111111111111")
sb.Append("11111111111111111111111111111111")
sb.Append("11111111111111111111111111111111")
sb.Append("11111111111111111111111111111111")
sb.Append("11111111111111111111111111111111")
sb.Append("11111111111111111111111111111111")
sb.Append("11111111111111111111111111111111")
sb.Append("11111111111111111111111111111111")
sb.Append("11111111111111111111111111111111")
sb.Append("11111111111111111111111111111111")
sb.Append("11111111111111111111111111111111")
Next
System.Windows.Forms.MessageBox.Show(CStr(DateAndT ime.Timer -
tStart))

Dim s As String = ""
tStart = DateAndTime.Timer
For i As Integer = 1 To 5000
s &= "11111111111111111111111111111111" & _
"11111111111111111111111111111111" & _
"11111111111111111111111111111111" & _
"11111111111111111111111111111111" & _
"11111111111111111111111111111111" & _
"11111111111111111111111111111111" & _
"11111111111111111111111111111111" & _
"11111111111111111111111111111111" & _
"11111111111111111111111111111111" & _
"11111111111111111111111111111111" & _
"11111111111111111111111111111111" & _
"11111111111111111111111111111111" & _
"11111111111111111111111111111111" & _
"11111111111111111111111111111111" & _
"11111111111111111111111111111111" & _
"11111111111111111111111111111111" & _
"11111111111111111111111111111111" & _
"11111111111111111111111111111111" & _
"11111111111111111111111111111111" & _
"11111111111111111111111111111111"
Next
System.Windows.Forms.MessageBox.Show(CStr(DateAndT ime.Timer -
tStart))

Thanks
JCVoon

Nov 21 '05 #5

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