diff --git a/src/Parallel/test/clr_parallelTask_demo.vb b/src/Parallel/test/clr_parallelTask_demo.vb
index fb13679..b07af29 100644
--- a/src/Parallel/test/clr_parallelTask_demo.vb
+++ b/src/Parallel/test/clr_parallelTask_demo.vb
@@ -1,7 +1,7 @@
 Imports batch
 Imports Microsoft.VisualBasic.Math
 Imports Microsoft.VisualBasic.Math.Correlations
-Imports Parallel
+Imports Microsoft.VisualBasic.MIME.application.json
 Imports Parallel.IpcStream
 Imports rnd = Microsoft.VisualBasic.Math.RandomExtensions
 
@@ -30,10 +30,13 @@ Module clr_parallelTask_demo
         Call Console.WriteLine("memory data create job done!")
         Call Console.WriteLine("create parallrl task...")
 
-        Dim snowFall As SlaveTask = Host.CreateSlave(verbose:=True)
+        Dim args As New Argument(4)
         Dim memory_symbol1 As SocketRef = SocketRef.WriteBuffer(pool)
+        Dim result = Host.ParallelFor(Of vectorData, Double())(args, New Func(Of vectorData, vectorData(), Double())(AddressOf compute_function), pool, memory_symbol1)
 
-
+        For Each item In result
+            Call Console.WriteLine(item.GetJson)
+        Next
     End Sub
 End Module
 
diff --git a/src/batch/Host/Argument.vb b/src/batch/Host/Argument.vb
index 950a868..f2b53b7 100644
--- a/src/batch/Host/Argument.vb
+++ b/src/batch/Host/Argument.vb
@@ -8,6 +8,13 @@ Public Class Argument
     Public Property ignoreError As Boolean = False
     Public Property n_threads As Integer = 32
 
+    Sub New()
+    End Sub
+
+    Sub New(n_threads As Integer)
+        Me.n_threads = n_threads
+    End Sub
+
     Public Overrides Function ToString() As String
         Return Me.GetJson
     End Function
diff --git a/src/batch/Host/Host.vb b/src/batch/Host/Host.vb
index 1488b58..7fc1c7d 100644
--- a/src/batch/Host/Host.vb
+++ b/src/batch/Host/Host.vb
@@ -55,9 +55,12 @@ Public Module Host
     End Function
 
     <Extension>
-    Public Function ParallelFor(Of T)(par As Argument, task As [Delegate], [loop] As SocketRef(), ParamArray args As SocketRef()) As IEnumerable(Of T)
+    Public Function ParallelFor(Of I, T)(par As Argument, task As [Delegate], [loop] As I(), ParamArray args As SocketRef()) As IEnumerable(Of T)
         Dim foreach As New ParallelFor(Of T)(par)
-        Dim run = batch.ParallelFor(Of T).CreateFunction(par, task, [loop], args)
+        Dim loopVal As SocketRef() = [loop] _
+            .Select(Function(obj) SocketRef.WriteBuffer(obj)) _
+            .ToArray
+        Dim run = batch.ParallelFor(Of T).CreateFunction(par, task, loopVal, args)
 
         Return foreach.GetResult(run)
     End Function