Trying to make a custom parallel foreach

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I am trying to make a custom parallel for each statement to incorporate into a dll file.

I am having a hard time creating an object that displays as an delegate. I need the name to pass into the address of portion of the parallel for each statement.
I am trying to pass the name of the delegate as a string through the sub. The issue is I can not figure how to make the result variable useable in the address of.

Public Sub parallelforeach(startofiteration As Long, endofiteration As Long, subfunctionname As String)
       Dim result As [delegate]


       result = CallByName(Me, subfunctionname, CallType.Get, Nothing)
       ' CallByName()
       Dim numbers() = Enumerable.Range(startofiteration, endofiteration).ToArray
       ' CallByName(yourClassOrObjectName, "NameExample1", CallType.Set, oReader.ReadString)
       ' System.Threading.Tasks.Parallel.ForEach(numbers, processorcount, AddressOf process)
   End Sub

I am getting this error,

System.MissingMemberException: 'Public member 'process' on type 'Form1' not found.'

I was trying to find information on delegates and address of. Not much out there on the type of thing I am trying to accomplish.

What I have tried:

I have tried changing the delegate to an object. I have also tried to change the type.get to type.method see if that would help.

Posted 4-Aug-19 8:42am

Member 11856456

Updated 8-Aug-19 7:10am

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2 solutions

Solution 1

Does your "Form1" have a "public" member called "process"?

How about a private one that you can make public?

Or, add one to Form1 and see what happens when it gets "called".

Quote:
'? System.Threading.Tasks.Parallel.ForEach(numbers, processorcount, AddressOf process)

Posted 4-Aug-19 10:21am

Gerry Schmitz

Updated 4-Aug-19 10:23am

v2

Comments

Member 11856456 4-Aug-19 18:57pm

yes,
Private Sub process(i As Long)
end sub

I changed the private to public and got a new message:
System.MissingMemberException: 'Overload resolution failed because no accessible 'process' accepts this number of arguments.'

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Richard Deeming · Accepted Answer · 2019-08-08T07:10:00

You need to create an Action(Of Integer) delegate given the name of a method on the current class:

VB.NET

Public Sub ParallelForEach(ByVal startOfIteration As Integer, ByVal endOfIteration As Integer, ByVal subFunctionName As String)
    
    Const flags As BindingFlags = BindingFlags.Public Or BindingFlags.NonPublic Or BindingFlags.Static Or BindingFlags.Instance
    
    ' Find the method with the specified name which accepts a single Integer parameter:
    Dim method As MethodInfo = Me.GetType().GetMethod(subFunctionName, flags, Nothing, New Type() { GetType(Integer) }, Nothing)
    
    If method Is Nothing Then
        Throw New ArgumentException(String.Format("Method '{0}' was not found.", subFunctionName), "subFunctionName")
    End If

    ' Create a delegate of the correct type pointing to the method:
    Dim del As System.Delegate
    If method.IsStatic Then
        del = System.Delegate.CreateDelegate(GetType(Action(Of Integer)), method)
    Else
        del = System.Delegate.CreateDelegate(GetType(Action(Of Integer)), Me, method)
    End If
    
    ' Cast the delegate to the correct type:
    Dim action As Action(Of Integer) = DirectCast(del, Action(Of Integer))
    
    ' NB: Second parameter to Range is the number of items to return, not the last number to return:
    Dim numbers As IEnumerable(Of Integer) = Enumerable.Range(startOfIteration, 1 + endOfIteration - startOfIteration)
    
    System.Threading.Tasks.Parallel.ForEach(numbers, processorCount, action)
End Sub

NB: The parameters to Enumerable.Range are Integer (32-bit), not Long (64-bit).

Also, the second parameter is the number of items to return, not the last number to return. Your parameter names suggest you're passing in the last number to return, so you have to adjust for that.

Since you're iterating over a fixed set of numbers, it would probably be better to use Parallel.For[^] instead of Parallel.ForEach.