diff --git a/node_tree.py b/node_tree.py
index 97be769efb7b3b291f32ab37a68ae2b6c4a29577..5354cc9a95bc04691cfee56ca43a4798750f6ec8 100644
--- a/node_tree.py
+++ b/node_tree.py
@@ -82,6 +82,10 @@ class SvLinkNewNodeInput(bpy.types.Operator):
         return {'FINISHED'}
 
 
+
+
+
+
 @contextmanager
 def throttle_tree_update(node):
     """ usage
@@ -132,6 +136,35 @@ def throttled(func):
     return wrapper_update
 
 
+def poll_node(func):
+    """
+    this function is used to reject calls to node.update
+
+    use as a decorator:
+
+        from sverchok.node_tree import SverchCustomTreeNode, poll_node
+
+        class node:
+
+
+            def sv_poll(self):
+                ... test here to return True, if you want to avoid executing the update
+                ... function too early.
+                ... usually something like :   
+                ...      if 'last_output' in self.outputs: return True
+
+            @poll_node
+            def update(self):
+                ... stuff you do with a highly dynamic ui node
+
+
+    """
+    def wrapper_node_update(self):
+        if not self.sv_poll():
+            func(self)
+
+    return wrapper_node_update
+
 
 class SvNodeTreeCommon(object):
     '''
diff --git a/nodes/list_mutators/combinatorics.py b/nodes/list_mutators/combinatorics.py
index 5911eb344f258a3ec2e0e1a96a669a6d78e61d38..918aaf17e8b922cdbcc6c86741a4251b7f76cd60 100644
--- a/nodes/list_mutators/combinatorics.py
+++ b/nodes/list_mutators/combinatorics.py
@@ -19,10 +19,10 @@
 import bpy
 from bpy.props import IntProperty, EnumProperty
 
-from sverchok.node_tree import SverchCustomTreeNode
-from sverchok.data_structure import (match_long_repeat, updateNode)
+from sverchok.node_tree import SverchCustomTreeNode, poll_node
+from sverchok.data_structure import match_long_repeat, updateNode
 
-from itertools import (product, permutations, combinations)
+from itertools import product, permutations, combinations
 
 operations = {
     "PRODUCT":      (10, lambda s, r: product(*s, repeat=r)),
@@ -73,19 +73,21 @@ class SvCombinatoricsNode(bpy.types.Node, SverchCustomTreeNode):
         self.outputs.new('SvStringsSocket', "Result")
 
         self.update_operation(context)
-
-    def update(self):
-        ''' Add/remove sockets as A-Z sockets are connected/disconnected '''
+    
+    def sv_poll(self):
         if not 'Result' in self.outputs:
-            return
+            return True
 
         # not a multiple input operation ? => no need to update sockets
         if self.operation not in multiple_input_operations:
-            return
+            return True
 
-        inputs = self.inputs
+    @poll_node
+    def update(self):
+        ''' Add/remove sockets as A-Z sockets are connected/disconnected '''
 
         # get all existing A-Z sockets (connected or not)
+        inputs = self.inputs
         inputs_AZ = list(filter(lambda s: s.name in ABC, inputs))
 
         # last A-Z socket connected ? => add an empty A-Z socket at the end
@@ -98,7 +100,7 @@ class SvCombinatoricsNode(bpy.types.Node, SverchCustomTreeNode):
                 s = inputs_AZ[-1]
                 inputs.remove(s)
                 inputs_AZ.remove(s)
-
+    
     def update_sockets(self):
         ''' Update sockets based on selected operation '''