What's the difference between dim on the member level and static on the procedure level?
static, vb.net
Solution
Static local variables are a weird feature of VB.Net. When you compile them, they just get represented by a class level static variable behind the scenes.
However, if you're initializing and declaring a static local variable at the same time, what actually happens is the compiler sticks a Monitor class around it, to ensure that it can't be initialized by multiple threads at the same time.
It's the overhead of this Monitor that you're likely seeing. Try removing the initialization from the declarative statement and see if you notice a performance improvement.
Problem
In Visual Basic 2008, there's two different ways that I know of to accomplish the same thing: The Dim on the member level: ``` Dim counter1 as integer = 0 Dim counter2 as integer = 180 Public Sub SampleSub1() Counter1 += 1 : If (Counter1 > 14) Then Counter1 = 0 Counter2 += 1 : If (Counter2 > 240) Then Counter2 = 0 End Sub ``` Then there is the static on the procedure level: ``` Public Sub SampleSub2() Static Dim counter1 as integer = 0 Static Dim counter2 as integer = 180 Counter1 += 1 : If (Counter1 > 14) Then Counter1 = 0 Counter2 += 1 : If (Counter2 > 240) Then Counter2 = 0 End Sub ``` I'm running a loop about 8 million times through this in about 7 seconds (with more data being processed), and using the static method on the counters actually takes about 500ms longer. Does the static method provide better memory management? Why is it slower? Additionally, I declare my objects that are re-used with a dim on the member level or at least outside for loops, like: ``` Dim SampleObject as SampleClass Public Sub SampleSub3() SampleObject = TheQueue.Dequeue() End Sub ``` Should I use the Static method (which seems to be slower) on situations like this, or the dim on member level method that I already use? I've reproduced the problem with this code in a test app: ``` Public Class Form1 Dim EndLoop As Integer = 50000000 Dim stopwatch1 As New Stopwatch Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click stopwatch1.Reset() stopwatch1.Start() For cnt As Integer = 1 To EndLoop test1() Next stopwatch1.Stop() Label1.Text = "Loop1: " & stopwatch1.ElapsedMilliseconds stopwatch1.Reset() stopwatch1.Start() For cnt As Integer = 1 To EndLoop test2() Next stopwatch1.Stop() Label2.Text = "Loop2: " & stopwatch1.ElapsedMilliseconds End Sub End Class Public Module TestModule Dim counter1 As Integer = 0 Dim counter2 As Integer = 180 Public Sub test1() counter1 += 1 : If (counter1 > 14) Then counter1 = 0 counter2 += 1 : If (counter2 > 240) Then counter2 = 0 COW1(counter1, counter2) End Sub Public Sub test2() Static counter3 As Integer = 0 Static counter4 As Integer = 180 counter3 += 1 : If (counter3 > 14) Then counter3 = 0 counter4 += 1 : If (counter4 > 240) Then counter4 = 0 COW1(counter3, counter4) End Sub Public Sub COW1(ByVal counter1 As Integer, ByVal counter2 As Integer) End Sub End Module ``` The slow down with the usage of the static variables does not occur unless I'm calling a sub from another module like the above example.