diff --git a/src/TensorFlowNET.Core/Graphs/Graph.cs b/src/TensorFlowNET.Core/Graphs/Graph.cs
index 512e08c2..dca54511 100644
--- a/src/TensorFlowNET.Core/Graphs/Graph.cs
+++ b/src/TensorFlowNET.Core/Graphs/Graph.cs
@@ -77,9 +77,9 @@ namespace Tensorflow
 
             var temp_obj = _as_graph_element(obj);
 
-            if(obj is Tensor && allow_tensor)
+            if (obj is Tensor tensor && allow_tensor)
             {
-                if ((obj as Tensor).Graph.Equals(this))
+                if (tensor.Graph.Equals(this))
                 {
                     return obj;
                 }
@@ -88,6 +88,17 @@ namespace Tensorflow
                     throw new Exception($"Tensor {obj} is not an element of this graph.");
                 }
             }
+            else if (obj is Operation op && allow_operation)
+            {
+                if (op.Graph.Equals(this))
+                {
+                    return obj;
+                }
+                else
+                {
+                    throw new Exception($"Operation {obj} is not an element of this graph.");
+                }
+            }
 
             throw new Exception($"Can not convert a {typeof(T).Name} into a {types_str}.");
         }
diff --git a/src/TensorFlowNET.Core/Operations/control_flow_ops.py.cs b/src/TensorFlowNET.Core/Operations/control_flow_ops.py.cs
index b6fe4d78..37b91448 100644
--- a/src/TensorFlowNET.Core/Operations/control_flow_ops.py.cs
+++ b/src/TensorFlowNET.Core/Operations/control_flow_ops.py.cs
@@ -1,5 +1,6 @@
 using System;
 using System.Collections.Generic;
+using System.Linq;
 using System.Text;
 
 namespace Tensorflow
@@ -10,14 +11,35 @@ namespace Tensorflow
         {
             using(var namescope = new ops.name_scope<Operation>(name, "group_deps", inputs))
             {
+                name = namescope;
+
+                var ops_on_device = new Dictionary<string, Operation[]>();
+
                 // Sorts *inputs according to their devices.
+                foreach (var inp in inputs)
+                {
+                    ops_on_device[inp.Device] = new Operation[] { inp };
+                }
+
+                // 1-level tree. The root node is the returned NoOp node.
+                if (ops_on_device.Count == 1)
+                {
+                    return _GroupControlDeps(ops_on_device.Keys.First(), ops_on_device.Values.First(), name);
+                }
 
-                return _GroupControlDeps("", name);
+                // 2-level tree. The root node is the returned NoOp node.
+                // deps contains 1 NoOp node for each device.
+                return null;
             }
         }
 
-        private static Operation _GroupControlDeps(string dev, string name = "")
+        private static Operation _GroupControlDeps(string dev, Operation[] deps, string name = "")
         {
+            if (string.IsNullOrEmpty(dev))
+            {
+                return gen_control_flow_ops.no_op(name);
+            }
+
             return null;
         }
     }
diff --git a/src/TensorFlowNET.Core/Operations/gen_control_flow_ops.py.cs b/src/TensorFlowNET.Core/Operations/gen_control_flow_ops.py.cs
new file mode 100644
index 00000000..c17753dd
--- /dev/null
+++ b/src/TensorFlowNET.Core/Operations/gen_control_flow_ops.py.cs
@@ -0,0 +1,18 @@
+using System;
+using System.Collections.Generic;
+using System.Text;
+
+namespace Tensorflow
+{
+    public class gen_control_flow_ops
+    {
+        public static OpDefLibrary _op_def_lib = new OpDefLibrary();
+
+        public static Operation no_op(string name = "")
+        {
+            var _op = _op_def_lib._apply_op_helper("NoOp", name);
+
+            return _op;
+        }
+    }
+}
diff --git a/src/TensorFlowNET.Core/Sessions/BaseSession.cs b/src/TensorFlowNET.Core/Sessions/BaseSession.cs
index 3208c349..7460dea1 100644
--- a/src/TensorFlowNET.Core/Sessions/BaseSession.cs
+++ b/src/TensorFlowNET.Core/Sessions/BaseSession.cs
@@ -40,7 +40,12 @@ namespace Tensorflow
             return _run(fetches, feed_dict);
         }
 
-        private NDArray _run(Tensor fetches, Dictionary<Tensor, NDArray> feed_dict = null)
+        public virtual NDArray run(Operation fetches, Dictionary<Tensor, NDArray> feed_dict = null)
+        {
+            return _run(fetches, feed_dict);
+        }
+
+        private NDArray _run<T>(T fetches, Dictionary<Tensor, NDArray> feed_dict = null)
         {
             var feed_dict_tensor = new Dictionary<Tensor, NDArray>();
 
@@ -53,7 +58,7 @@ namespace Tensorflow
             }
 
             // Create a fetch handler to take care of the structure of fetches.
-            var fetch_handler = new _FetchHandler(_graph, fetches, feed_dict_tensor);
+            var fetch_handler = new _FetchHandler<T>(_graph, fetches, feed_dict_tensor);
 
             // Run request and get response.
             // We need to keep the returned movers alive for the following _do_run().
@@ -65,20 +70,34 @@ namespace Tensorflow
 
             // We only want to really perform the run if fetches or targets are provided,
             // or if the call is a partial run that specifies feeds.
-            var results = _do_run(final_fetches, feed_dict_tensor);
+            var results = _do_run(final_targets.Select(x => (Operation)(object)x).ToList(), final_fetches, feed_dict_tensor);
 
             return fetch_handler.build_results(null, results);
         }
 
-        private NDArray[] _do_run(List<Tensor> fetch_list, Dictionary<Tensor, NDArray> feed_dict)
+        /// <summary>
+        /// Runs a step based on the given fetches and feeds.
+        /// </summary>
+        /// <typeparam name="T"></typeparam>
+        /// <param name="target_list">A list of operations to be run, but not fetched.</param>
+        /// <param name="fetch_list"></param>
+        /// <param name="feed_dict"></param>
+        /// <returns>
+        /// A list of numpy ndarrays, corresponding to the elements of
+        /// `fetch_list`.  If the ith element of `fetch_list` contains the
+        /// name of an operation, the first Tensor output of that operation
+        /// will be returned for that element.
+        /// </returns>
+        private NDArray[] _do_run(List<Operation> target_list, List<Tensor> fetch_list, Dictionary<Tensor, NDArray> feed_dict)
         {
             var feeds = feed_dict.Select(x => new KeyValuePair<TF_Output, Tensor>(x.Key._as_tf_output(), new Tensor(x.Value))).ToArray();
             var fetches = fetch_list.Select(x => x._as_tf_output()).ToArray();
+            var targets = target_list;
 
-            return _call_tf_sessionrun(feeds, fetches);
+            return _call_tf_sessionrun(feeds, fetches, target_list);
         }
 
-        private unsafe NDArray[] _call_tf_sessionrun(KeyValuePair<TF_Output, Tensor>[] feed_dict, TF_Output[] fetch_list)
+        private unsafe NDArray[] _call_tf_sessionrun(KeyValuePair<TF_Output, Tensor>[] feed_dict, TF_Output[] fetch_list, List<Operation> target_list)
         {
             // Ensure any changes to the graph are reflected in the runtime.
             _extend_graph();
@@ -95,8 +114,8 @@ namespace Tensorflow
                 outputs: fetch_list,
                 output_values: output_values,
                 noutputs: fetch_list.Length,
-                target_opers: IntPtr.Zero,
-                ntargets: 0,
+                target_opers: target_list.Select(f => (IntPtr)f).ToArray(),
+                ntargets: target_list.Count,
                 run_metadata: IntPtr.Zero,
                 status: status);
 
diff --git a/src/TensorFlowNET.Core/Sessions/_ElementFetchMapper.cs b/src/TensorFlowNET.Core/Sessions/_ElementFetchMapper.cs
index 83068972..41f67417 100644
--- a/src/TensorFlowNET.Core/Sessions/_ElementFetchMapper.cs
+++ b/src/TensorFlowNET.Core/Sessions/_ElementFetchMapper.cs
@@ -8,26 +8,37 @@ namespace Tensorflow
     /// <summary>
     /// Fetch mapper for singleton tensors and ops.
     /// </summary>
-    public class _ElementFetchMapper : _FetchMapper
+    public class _ElementFetchMapper<T> : _FetchMapper<T>
     {
-        private List<Object> _unique_fetches = new List<object>();
-        private Action _contraction_fn;
+        private List<object> _unique_fetches = new List<object>();
+        private Func<List<object>> _contraction_fn;
 
-        public _ElementFetchMapper(List<Tensor> fetches, Action contraction_fn)
+        public _ElementFetchMapper(List<T> fetches, Func<List<object>> contraction_fn)
         {
-            foreach(var tensor in fetches)
+            foreach(var fetch in fetches)
             {
-                var fetch = ops.get_default_graph().as_graph_element(tensor, allow_tensor: true, allow_operation: true);
-                _unique_fetches.Add(fetch);
+                var g = ops.get_default_graph();
+                var el = g.as_graph_element(fetch, allow_tensor: true, allow_operation: true);
+                _unique_fetches.Add(el);
             }
+
+            _contraction_fn = contraction_fn;
         }
 
-        public NDArray build_results(NDArray[] values)
+        /// <summary>
+        /// Build results matching the original fetch shape.
+        /// </summary>
+        /// <param name="values"></param>
+        /// <returns></returns>
+        public NDArray build_results(List<object> values)
         {
-            return values[0];
+            if (values.Count == 0)
+                return null;
+            else
+                return _contraction_fn(values);
         }
 
-        public List<Object> unique_fetches()
+        public List<object> unique_fetches()
         {
             return _unique_fetches;
         }
diff --git a/src/TensorFlowNET.Core/Sessions/_FetchHandler.cs b/src/TensorFlowNET.Core/Sessions/_FetchHandler.cs
index 1da14507..4e709f76 100644
--- a/src/TensorFlowNET.Core/Sessions/_FetchHandler.cs
+++ b/src/TensorFlowNET.Core/Sessions/_FetchHandler.cs
@@ -8,21 +8,26 @@ namespace Tensorflow
     /// <summary>
     /// Handler for structured fetches.
     /// </summary>
-    public class _FetchHandler
+    public class _FetchHandler<T>
     {
-        private _ElementFetchMapper _fetch_mapper;
+        private _ElementFetchMapper<T> _fetch_mapper;
         private List<Tensor> _fetches = new List<Tensor>();
         private List<bool> _ops = new List<bool>();
         private List<Tensor> _final_fetches = new List<Tensor>();
-        private List<object> _targets = new List<object>();
+        private List<T> _targets = new List<T>();
 
-        public _FetchHandler(Graph graph, Tensor fetches, Dictionary<Tensor, NDArray> feeds = null, object feed_handles = null)
+        public _FetchHandler(Graph graph, T fetches, Dictionary<Tensor, NDArray> feeds = null, object feed_handles = null)
         {
-            _fetch_mapper = new _FetchMapper().for_fetch(fetches);
+            _fetch_mapper = new _FetchMapper<T>().for_fetch(fetches);
             foreach(var fetch in _fetch_mapper.unique_fetches())
             {
                 switch (fetch)
                 {
+                    case Operation val:
+                        _assert_fetchable(graph, val);
+                        _targets.Add((T)(object)val);
+                        _ops.Add(true);
+                        break;
                     case Tensor val:
                         _assert_fetchable(graph, val.op);
                         _fetches.Add(val);
@@ -35,9 +40,19 @@ namespace Tensorflow
             _final_fetches = _fetches;
         }
 
-        public NDArray build_results(Session session, NDArray[] results)
+        public NDArray build_results(Session session, NDArray[] tensor_values)
         {
-            return _fetch_mapper.build_results(results);
+            var full_values = new List<object>();
+
+            foreach(var is_op in _ops)
+            {
+                if (is_op)
+                {
+                    full_values.Add(null);
+                }
+            }
+
+            return _fetch_mapper.build_results(full_values);
         }
 
         private void _assert_fetchable(Graph graph, Operation op)
@@ -53,7 +68,7 @@ namespace Tensorflow
             return _final_fetches;
         }
 
-        public List<Object> targets()
+        public List<T> targets()
         {
             return _targets;
         }
diff --git a/src/TensorFlowNET.Core/Sessions/_FetchMapper.cs b/src/TensorFlowNET.Core/Sessions/_FetchMapper.cs
index 763b67a0..fbad8db6 100644
--- a/src/TensorFlowNET.Core/Sessions/_FetchMapper.cs
+++ b/src/TensorFlowNET.Core/Sessions/_FetchMapper.cs
@@ -4,13 +4,13 @@ using System.Text;
 
 namespace Tensorflow
 {
-    public class _FetchMapper
+    public class _FetchMapper<T>
     {
-        public _ElementFetchMapper for_fetch(Tensor fetch)
+        public _ElementFetchMapper<T> for_fetch(T fetch)
         {
-            var fetches = new List<Tensor> { fetch };
+            var fetches = new List<T> { fetch };
 
-            return new _ElementFetchMapper(fetches, null);
+            return new _ElementFetchMapper<T>(fetches, null);
         }
     }
 }
diff --git a/src/TensorFlowNET.Core/Sessions/c_api.session.cs b/src/TensorFlowNET.Core/Sessions/c_api.session.cs
index 3fc20365..b1860cd2 100644
--- a/src/TensorFlowNET.Core/Sessions/c_api.session.cs
+++ b/src/TensorFlowNET.Core/Sessions/c_api.session.cs
@@ -87,7 +87,7 @@ namespace Tensorflow
         public static extern unsafe void TF_SessionRun(IntPtr session, TF_Buffer* run_options,
                    TF_Output[] inputs, IntPtr[] input_values, int ninputs,
                    TF_Output[] outputs, IntPtr[] output_values, int noutputs,
-                   IntPtr target_opers, int ntargets,
+                   IntPtr[] target_opers, int ntargets,
                    IntPtr run_metadata,
                    IntPtr status);
     }
diff --git a/src/TensorFlowNET.Core/Variables/variables.py.cs b/src/TensorFlowNET.Core/Variables/variables.py.cs
index ecb635ce..ea317a89 100644
--- a/src/TensorFlowNET.Core/Variables/variables.py.cs
+++ b/src/TensorFlowNET.Core/Variables/variables.py.cs
@@ -42,7 +42,7 @@ namespace Tensorflow
         /// <returns>An Op that run the initializers of all the specified variables.</returns>
         public static Operation variables_initializer(RefVariable[] var_list, string name = "init")
         {
-            return control_flow_ops.group(var_list.Select(x => x.initializer).ToList());
+            return control_flow_ops.group(var_list.Select(x => x.initializer).ToList(), name);
         }
     }
 }
diff --git a/src/TensorFlowNET.Core/runtimes/win-x64/native/tensorflow.dll b/src/TensorFlowNET.Core/runtimes/win-x64/native/tensorflow.dll
index d667cffa..4c62c8ce 100644
Binary files a/src/TensorFlowNET.Core/runtimes/win-x64/native/tensorflow.dll and b/src/TensorFlowNET.Core/runtimes/win-x64/native/tensorflow.dll differ
diff --git a/test/TensorFlowNET.UnitTest/CSession.cs b/test/TensorFlowNET.UnitTest/CSession.cs
index 70e549f3..77de6b6b 100644
--- a/test/TensorFlowNET.UnitTest/CSession.cs
+++ b/test/TensorFlowNET.UnitTest/CSession.cs
@@ -76,7 +76,7 @@ namespace TensorFlowNET.UnitTest
             var input_values_ptr = input_values_.Select(x => (IntPtr)x).ToArray();
             var outputs_ptr = outputs_.ToArray();
             var output_values_ptr = output_values_.Select(x => (IntPtr)x).ToArray();
-            IntPtr targets_ptr = IntPtr.Zero;
+            IntPtr[] targets_ptr = new IntPtr[0];
 
             c_api.TF_SessionRun(session_, null, inputs_ptr, input_values_ptr, inputs_ptr.Length,
                 outputs_ptr, output_values_ptr, outputs_.Count, 
diff --git a/test/TensorFlowNET.UnitTest/VariableTest.cs b/test/TensorFlowNET.UnitTest/VariableTest.cs
index f316c3f0..c5d40b75 100644
--- a/test/TensorFlowNET.UnitTest/VariableTest.cs
+++ b/test/TensorFlowNET.UnitTest/VariableTest.cs
@@ -35,13 +35,13 @@ namespace TensorFlowNET.UnitTest
 
             using (var session = tf.Session())
             {
-                /*session.run(model);
+                session.run(model);
                 for(int i = 0; i < 5; i++)
                 {
-                    x = x + 1;
+                    //x = x + 1;
                     var result = session.run(x);
                     print(result);
-                }*/
+                }
             }
 
         }