diff --git a/nnvm/include/nnvm/symbolic.h b/nnvm/include/nnvm/symbolic.h
index 5f2deaf948a6..2d5867a11892 100644
--- a/nnvm/include/nnvm/symbolic.h
+++ b/nnvm/include/nnvm/symbolic.h
@@ -73,8 +73,8 @@ class Symbol {
    * \param kwargs keyword arguments for the symbol
    * \param name name of returned symbol.
    */
-  void Compose(const std::vector<Symbol>& args,
-               const std::unordered_map<std::string, Symbol>& kwargs,
+  void Compose(const array_view<const Symbol*>& args,
+               const std::unordered_map<std::string, const Symbol*>& kwargs,
                const std::string& name);
   /*!
    * \brief Apply the symbol as a function, compose with arguments
@@ -84,8 +84,8 @@ class Symbol {
    * \param name name of returned symbol.
    * \return a new Symbol which is the composition of current symbol with its arguments
    */
-  Symbol operator () (const std::vector<Symbol>& args,
-                      const std::unordered_map<std::string, Symbol>& kwargs,
+  Symbol operator () (const array_view<const Symbol*>& args,
+                      const std::unordered_map<std::string, const Symbol*>& kwargs,
                       const std::string& name) const;
   /*!
    * \brief Add control flow depenencies to operators involved in symbols.
diff --git a/nnvm/src/c_api/c_api_common.h b/nnvm/src/c_api/c_api_common.h
index 170ceb2e58d3..40c91d8ffc11 100644
--- a/nnvm/src/c_api/c_api_common.h
+++ b/nnvm/src/c_api/c_api_common.h
@@ -10,6 +10,7 @@
 #include <dmlc/logging.h>
 #include <dmlc/thread_local.h>
 #include <nnvm/c_api.h>
+#include <nnvm/symbolic.h>
 #include <vector>
 #include <string>
 
@@ -36,6 +37,8 @@ struct NNAPIThreadLocalEntry {
   std::vector<const char *> ret_vec_charp;
   /*! \brief result holder for returning handles */
   std::vector<void *> ret_handles;
+  /*! \brief argument holder to hold symbol */
+  std::unordered_map<std::string, const nnvm::Symbol*> kwarg_symbol;
 };
 
 /*! \brief Thread local store that can be used to hold return values. */
diff --git a/nnvm/src/c_api/c_api_symbolic.cc b/nnvm/src/c_api/c_api_symbolic.cc
index 335d163c7dae..bc6eed5c742a 100644
--- a/nnvm/src/c_api/c_api_symbolic.cc
+++ b/nnvm/src/c_api/c_api_symbolic.cc
@@ -217,22 +217,26 @@ int NNSymbolCompose(SymbolHandle sym,
                     const char** keys,
                     SymbolHandle* args) {
   API_BEGIN();
-  std::string s_name;
-  if (name != nullptr) s_name = name;
-
+  NNAPIThreadLocalEntry *ret = NNAPIThreadLocalStore::Get();
+  std::string& s_name = ret->ret_str;
+  std::unordered_map<std::string, const Symbol*>& kwargs
+      = ret->kwarg_symbol;
+  if (name != nullptr) {
+    s_name = name;
+  } else {
+    s_name.clear();
+  }
   Symbol* s = static_cast<Symbol*>(sym);
   if (keys == nullptr && num_args != 0) {
-    std::vector<Symbol> pos_args;
-    for (nn_uint i = 0; i < num_args; ++i) {
-      pos_args.push_back(*((Symbol*)args[i]));  //  NOLINT(*)
-    }
-    s->Compose(pos_args, {}, s_name);
+    kwargs.clear();
+    array_view<const Symbol*> parg(
+        (Symbol**)args, (Symbol**)args + num_args); // NOLINT(*)
+    s->Compose(parg, kwargs, s_name);
   } else {
-    std::unordered_map<std::string, Symbol> kwargs;
     for (nn_uint i = 0; i < num_args; ++i) {
-      kwargs[keys[i]] = *((Symbol*)args[i]);  //  NOLINT(*)
+      kwargs[keys[i]] = (Symbol*)args[i];  //  NOLINT(*)
     }
-    s->Compose({}, kwargs, s_name);
+    s->Compose(array_view<const Symbol*>(), kwargs, s_name);
   }
   API_END();
 }
diff --git a/nnvm/src/core/symbolic.cc b/nnvm/src/core/symbolic.cc
index 0d6f2a6c786e..3cd1d982e433 100644
--- a/nnvm/src/core/symbolic.cc
+++ b/nnvm/src/core/symbolic.cc
@@ -45,7 +45,7 @@ inline void UpdateNodeVersion(Node *n) {
         CHECK(e.node->is_variable())
             << "Mutation target can only be Variable";
         // increase the version of the variable.
-        ++nnvm::get<VariableParam>(e.node->attrs.parsed).version;
+        e.version = ++nnvm::get<VariableParam>(e.node->attrs.parsed).version;
       }
     }
   }
@@ -98,7 +98,10 @@ Symbol Symbol::Copy() const {
   std::unordered_map<Node*, std::shared_ptr<Node> > old_new;
   // use DFSVisit to copy all the nodes
   DFSVisit(this->outputs, [&old_new](const std::shared_ptr<Node>& node) {
-      old_new[node.get()] =  std::make_shared<Node>(*node);
+      std::shared_ptr<Node> np = Node::Create();
+      np->op = node->op;
+      np->attrs = node->attrs;
+      old_new[node.get()] = std::move(np);
     });
   // connect nodes of new graph
   for (const auto &kv : old_new) {
@@ -106,6 +109,9 @@ Symbol Symbol::Copy() const {
       Node *ptr = e.node.get();
       kv.second->inputs.emplace_back(NodeEntry{old_new[ptr], e.index, e.version});
     }
+    for (const std::shared_ptr<Node>& p : kv.first->control_deps) {
+      kv.second->control_deps.emplace_back(old_new[p.get()]);
+    }
   }
   // set the head
   Symbol ret;
@@ -120,7 +126,7 @@ void Symbol::Print(std::ostream &os) const {
     os << "AtomicFunctor "<< " Op:" << outputs[0].node->op->name << '\n';
   } else {
     // use DFSVisit to copy all the nodes
-    os << "Outputs:\n";
+    os << "Symbol Outputs:\n";
     for (size_t i = 0; i < outputs.size(); ++i) {
       os << "\toutput[" << i << "]=" << outputs[i].node->attrs.name
          << '(' << outputs[i].index << ")\n";
@@ -129,7 +135,8 @@ void Symbol::Print(std::ostream &os) const {
         if (node->is_variable()) {
           os << "Variable:" << node->attrs.name << '\n';
         } else {
-          os << "Name: " << node->attrs.name << " Op:" << node->op->name << '\n'
+          os << "--------------------\n";
+          os << "Op:" << node->op->name << ", Name=" << node->attrs.name << '\n'
              << "Inputs:\n";
           for (size_t i = 0; i < node->inputs.size(); ++i) {
             const NodeEntry& e = node->inputs[i];
@@ -141,9 +148,17 @@ void Symbol::Print(std::ostream &os) const {
               os << '\n';
             }
           }
-          os << "Attrs:\n";
-          for (auto &kv : node->attrs.dict) {
-            os << '\t' << kv.first << '=' << kv.second << '\n';
+          if (!node->attrs.dict.empty()) {
+            os << "Attrs:\n";
+            for (auto &kv : node->attrs.dict) {
+              os << '\t' << kv.first << '=' << kv.second << '\n';
+            }
+          }
+          if (node->control_deps.size() != 0) {
+            os << "Control deps:\n";
+            for (size_t i = 0; i < node->control_deps.size(); ++i) {
+              os << "\tcdep[" << i << "]=" << node->control_deps[i]->attrs.name << '\n';
+            }
           }
         }
       });
@@ -203,8 +218,8 @@ std::vector<std::string> Symbol::ListOutputs() const {
 }
 
 // compositional logic
-void Symbol::Compose(const std::vector<Symbol>& args,
-                     const std::unordered_map<std::string, Symbol>& kwargs,
+void Symbol::Compose(const array_view<const Symbol*>& args,
+                     const std::unordered_map<std::string, const Symbol*>& kwargs,
                      const std::string& name) {
   static auto& flist_inputs = Op::GetAttr<FListInputNames>("FListInputNames");
 
@@ -213,11 +228,11 @@ void Symbol::Compose(const std::vector<Symbol>& args,
   CHECK(!outputs[0].node->is_variable()) << "Variable cannot be composed";
   // parameter check.
   for (size_t i = 0; i < args.size(); ++i) {
-    CHECK_EQ(args[i].outputs.size(), 1)
+    CHECK_EQ(args[i]->outputs.size(), 1)
         << "Argument " << i << " is a tuple, single value is required";
   }
   for (const auto& kv : kwargs) {
-    CHECK_EQ(kv.second.outputs.size(), 1)
+    CHECK_EQ(kv.second->outputs.size(), 1)
         << "Keyword Argument " << kv.first << " is a tuple, single value is required";
   }
   // assign new name
@@ -234,7 +249,7 @@ void Symbol::Compose(const std::vector<Symbol>& args,
           << "Incorrect number of arguments, requires " << n_req
           << ", provided " << args.size();
       for (size_t i = 0; i < args.size(); ++i) {
-        n->inputs[i] = args[i].outputs[0];
+        n->inputs[i] = args[i]->outputs[0];
       }
       // switch to keyword argument matching
       if (args.size() != n_req) {
@@ -247,7 +262,7 @@ void Symbol::Compose(const std::vector<Symbol>& args,
         for (size_t i = args.size(); i < n_req; ++i) {
           auto it = kwargs.find(arg_names[i]);
           if (it != kwargs.end() && it->first == arg_names[i]) {
-            n->inputs[i] = it->second.outputs[0];
+            n->inputs[i] = it->second->outputs[0];
             ++nmatched;
           } else {
             n->inputs[i] = NodeEntry{
@@ -266,8 +281,8 @@ void Symbol::Compose(const std::vector<Symbol>& args,
     } else {
       CHECK_EQ(kwargs.size(), 0) << "Variable length function do not accept kwargs";
       n->inputs.reserve(args.size());
-      for (const Symbol& s : args) {
-        n->inputs.push_back(s.outputs[0]);
+      for (const Symbol* s : args) {
+        n->inputs.push_back(s->outputs[0]);
       }
     }
     UpdateNodeVersion(n);
@@ -283,13 +298,13 @@ void Symbol::Compose(const std::vector<Symbol>& args,
         (const std::shared_ptr<Node> &node) {
       if (node->is_variable()) {
         if (arg_counter < args.size()) {
-          replace_map[node.get()] = &(args[arg_counter].outputs[0]);
+          replace_map[node.get()] = &(args[arg_counter]->outputs[0]);
           ++arg_counter;
         } else {
             // match kwargs
           auto kit = kwargs.find(node->attrs.name);
           if (kit != kwargs.end()) {
-            replace_map[node.get()] = &(kit->second.outputs[0]);
+            replace_map[node.get()] = &(kit->second->outputs[0]);
             ++nmatched;
           }
         }
@@ -334,8 +349,8 @@ void Symbol::Compose(const std::vector<Symbol>& args,
   }
 }
 
-Symbol Symbol::operator () (const std::vector<Symbol>& args,
-                            const std::unordered_map<std::string, Symbol>& kwargs,
+Symbol Symbol::operator () (const array_view<const Symbol*>& args,
+                            const std::unordered_map<std::string, const Symbol*>& kwargs,
                             const std::string& name) const {
   Symbol s = this->Copy();
   s.Compose(args, kwargs, name);
diff --git a/nnvm/src/pass/order_mutation.cc b/nnvm/src/pass/order_mutation.cc
new file mode 100644
index 000000000000..d0d527472389
--- /dev/null
+++ b/nnvm/src/pass/order_mutation.cc
@@ -0,0 +1,142 @@
+/*!
+ *  Copyright (c) 2016 by Contributors
+ * \file saveload_json.cc
+ * \brief Add control flow dependencies between nodes
+ *  To correctly order mutation and read to resolve
+ *  write after read problem and read after write problems.
+ */
+#include <nnvm/pass.h>
+#include <nnvm/op_attr_types.h>
+
+namespace nnvm {
+
+template<typename T>
+inline T get_with_default(const std::unordered_map<Node*, T> &map,
+                          Node* key,
+                          const T& def) {
+  auto it = map.find(key);
+  if (it != map.end()) return it->second;
+  return def;
+}
+
+Graph OrderMutation(const Graph& src) {
+  std::unordered_map<Node*, std::vector<NodeEntry> > version_hist;
+  DFSVisit(src.outputs, [&version_hist](const std::shared_ptr<Node>& n) {
+      for (const NodeEntry& e : n->inputs) {
+        if (e.node->is_variable()) {
+          if (e.version != 0 && version_hist.count(e.node.get()) == 0) {
+            version_hist[e.node.get()] = std::vector<NodeEntry>{};
+          }
+        }
+      }
+    });
+  // no mutation happens, everything if fine.
+  if (version_hist.size() == 0) return src;
+  // start preparing for remapping the nodes.
+  std::unordered_map<Node*, std::shared_ptr<Node> > old_new;
+  auto prepare = [&version_hist, &old_new] (const std::shared_ptr<Node>& n) {
+    static auto& fmutate_inputs = Op::GetAttr<FMutateInput>("FMutateInput");
+    bool need_repl = false;
+    for (size_t i = 0; i < n->inputs.size(); ++i) {
+      const NodeEntry& e = n->inputs[i];
+      if (e.node->is_variable()) {
+        if (e.version != 0) need_repl = true;
+        auto it = version_hist.find(e.node.get());
+        if (it != version_hist.end()) {
+          std::vector<NodeEntry>& vec = it->second;
+          uint32_t is_mutate =
+              fmutate_inputs.count(n->op) ? fmutate_inputs[n->op](n->attrs, i) : 0;
+          vec.emplace_back(NodeEntry{n, is_mutate, e.version});
+        }
+      } else {
+        if (old_new.count(e.node.get()) != 0) need_repl = true;
+      }
+    }
+    for (const std::shared_ptr<Node>& p : n->control_deps) {
+      if (old_new.count(p.get()) != 0) need_repl = true;
+    }
+    if (need_repl) {
+      std::shared_ptr<Node> np = Node::Create();
+      np->op = n->op;
+      np->attrs = n->attrs;
+      old_new[n.get()] = std::move(np);
+    }
+  };
+  DFSVisit(src.outputs, prepare);
+  // comparator of history entry
+  auto comparator = [](const NodeEntry& a, const NodeEntry &b) {
+    if (a.version < b.version) return true;
+    if (a.version > b.version) return false;
+    return a.index > b.index;
+  };
+
+  for (auto &kv : version_hist) {
+    std::sort(kv.second.begin(), kv.second.end(), comparator);
+  }
+  // copy the nodes, as well as add control deps
+  for (auto &kv : old_new) {
+    // copy the nodes
+    for (const NodeEntry& e : kv.first->inputs) {
+      auto it = old_new.find(e.node.get());
+      if (it != old_new.end()) {
+        kv.second->inputs.emplace_back(NodeEntry{it->second, e.index, e.version});
+      } else {
+        kv.second->inputs.push_back(e);
+      }
+    }
+    for (const std::shared_ptr<Node>& p : kv.first->control_deps) {
+      kv.second->control_deps.emplace_back(
+          get_with_default(old_new, p.get(), p));
+    }
+    // add control deps
+    static auto& fmutate_inputs = Op::GetAttr<FMutateInput>("FMutateInput");
+    for (size_t i = 0; i < kv.first->inputs.size(); ++i) {
+      const NodeEntry& e = kv.first->inputs[i];
+      if (e.node->is_variable() && version_hist.count(e.node.get()) != 0) {
+        FMutateInput fmutate = fmutate_inputs.get(kv.first->op, nullptr);
+        uint32_t is_mutate = (fmutate == nullptr) ? 0 : fmutate(kv.first->attrs, i);
+        std::vector<NodeEntry>& vec = version_hist.at(e.node.get());
+
+        auto it = std::lower_bound(vec.begin(), vec.end(),
+                                   NodeEntry{nullptr, 1, e.version},
+                                   comparator);
+        if (is_mutate != 0) {
+          int read_dep = 0;
+          while (it != vec.begin()) {
+            --it;
+            if (it->index != 0) break;
+            ++read_dep;
+            // depend on previous read
+            kv.second->control_deps.push_back(
+                get_with_default(old_new, it->node.get(), it->node));
+          }
+          if (read_dep == 0 && it->index != 0) {
+            // depend on last write
+            kv.second->control_deps.push_back(
+                get_with_default(old_new, it->node.get(), it->node));
+          }
+        } else {
+          // depend on last write
+          if (it->index != 0) {
+            kv.second->control_deps.push_back(
+                get_with_default(old_new, it->node.get(), it->node));
+          }
+        }
+      }
+    }
+  }
+  Graph ret;
+  for (const NodeEntry &e : src.outputs) {
+    ret.outputs.emplace_back(NodeEntry{
+        get_with_default(old_new, e.node.get(), e.node), e.index, e.version});
+  }
+  return ret;
+}
+
+NNVM_REGISTER_PASS(OrderMutation)
+.describe("Return a new graph that adds control dependencies, "\
+          "to order the mutation and reads if mutation exists.")
+.set_body(OrderMutation)
+.set_change_graph(true);
+
+}  // namespace nnvm
diff --git a/nnvm/src/pass/saveload_json.cc b/nnvm/src/pass/saveload_json.cc
index fee94fbf6eb9..4aa979e9cee9 100644
--- a/nnvm/src/pass/saveload_json.cc
+++ b/nnvm/src/pass/saveload_json.cc
@@ -1,7 +1,7 @@
 /*!
  *  Copyright (c) 2016 by Contributors
  * \file saveload_json.cc
- * \brief Passes that defines save and load graph to/from JSON file.
+ * \brief Save and load graph to/from JSON file.
  */
 #include <nnvm/pass.h>
 #include <dmlc/json.h>
diff --git a/nnvm/src/test_main.cc b/nnvm/src/test_main.cc
index 51d4ec1513cf..b79573c05513 100644
--- a/nnvm/src/test_main.cc
+++ b/nnvm/src/test_main.cc
@@ -2,42 +2,85 @@
 #include <nnvm/op.h>
 #include <nnvm/graph.h>
 #include <nnvm/tuple.h>
+#include <nnvm/c_api.h>
 #include <nnvm/graph_attr_types.h>
+#include <dmlc/timer.h>
 #include <string>
 
-void test_op() {
-  using namespace nnvm;
-  auto add = Op::Get("add");
-  static auto& nick = Op::GetAttr<std::string>("nick_name");
-  LOG(INFO) << "nick=" << nick[add];
+void test_speed() {
+  auto add = nnvm::Op::Get("add");
+  double tstart = dmlc::GetTime();
+  size_t rep = 1000;
+  size_t n = 1000;
+  std::unordered_map<std::string, const nnvm::Symbol*> tmp;
+  std::vector<const nnvm::Symbol*> vec{2};
+  std::string name = "xx";
+  for (size_t t = 0; t < rep; ++t) {
+    nnvm::Symbol s = nnvm::Symbol::CreateVariable("x");
+    for (size_t i = 0; i < n; ++i) {
+      nnvm::Symbol nw = nnvm::Symbol::CreateFunctor(add, {});
+      vec[0] = &s;
+      vec[1] =&s;
+      tmp.clear();
+      nw.Compose(vec, tmp, name);
+      s = nw;
+    }
+  }
+  double tend = dmlc::GetTime();
+  LOG(INFO) << "compose speed = " << n * rep / (tend - tstart) << " ops/sec";
 }
 
-void test_tuple() {
-  using nnvm::Tuple;
-  using nnvm::TShape;
-  Tuple<int> x{1, 2, 3};
-  Tuple<int> y{1, 2, 3, 5, 6};
-  x = std::move(y);
-
-  CHECK_EQ(x.ndim(), 5);
-  Tuple<int> z{1, 2, 3, 5, 6};
-  std::ostringstream os;
-  os << z;
-  CHECK_EQ(os.str(), "(1,2,3,5,6)");
-  std::istringstream is(os.str());
-  is >> y;
-  CHECK_EQ(x, y);
-  Tuple<nnvm::index_t> ss{1, 2, 3};
-  TShape s = ss;
-  s = std::move(ss);
-  CHECK((s == TShape{1, 2, 3}));
+void test_node_speed() {
+  using namespace nnvm;
+  auto add = nnvm::Op::Get("add");
+  double tstart = dmlc::GetTime();
+  size_t rep = 1000;
+  size_t n = 100;
+  for (size_t t = 0; t < rep; ++t) {
+    nnvm::Symbol s = nnvm::Symbol::CreateVariable("x");
+    for (size_t i = 0; i < n; ++i) {
+      auto xx = NodeEntry{Node::Create(), 0, 0};
+      NodeEntry x = s.outputs[0];
+      xx.node->op = add;
+      xx.node->inputs.emplace_back(x);
+      xx.node->inputs.emplace_back(x);
+      Symbol ss;
+      ss.outputs.push_back(xx);
+      s = ss;
+    }
+  }
+  double tend = dmlc::GetTime();
+  LOG(INFO) << "test_node_speed speed = " << n * rep / (tend - tstart) << " ops/sec";
 }
 
-
-void test_graph() {
-  nnvm::Symbol s;
+void test_api_speed() {
+  auto add = (void*)nnvm::Op::Get("add");  // NOLINT(*)
+  double tstart = dmlc::GetTime();
+  size_t rep = 1000;
+  size_t n = 1000;
+  std::unordered_map<std::string, const nnvm::Symbol*> tmp;
+  std::vector<const nnvm::Symbol*> vec{2};
+  std::string name = "xx";
+  for (size_t t = 0; t < rep; ++t) {
+    SymbolHandle s;
+    NNSymbolCreateVariable("xx", &s);
+    for (size_t i = 0; i < n; ++i) {
+      SymbolHandle arg[2];
+      SymbolHandle ss;
+      NNSymbolCreateAtomicSymbol(add, 0, nullptr, nullptr, &ss);
+      arg[0] = s;
+      arg[1] = s;
+      NNSymbolCompose(ss, "nn", 2, nullptr, arg);
+      s = ss;
+    }
+  }
+  double tend = dmlc::GetTime();
+  LOG(INFO) << "API compose speed = " << n * rep / (tend - tstart) << " ops/sec";
 }
+
 int main() {
-  test_tuple();
+  test_speed();
+  test_node_speed();
+  test_api_speed();
   return 0;
 }
diff --git a/nnvm/tests/python/test_graph.py b/nnvm/tests/python/test_graph.py
index 8fa392db3425..b6082364458e 100644
--- a/nnvm/tests/python/test_graph.py
+++ b/nnvm/tests/python/test_graph.py
@@ -1,3 +1,4 @@
+import json
 import nnvm.symbol as sym
 import nnvm.graph as graph
 
@@ -17,7 +18,24 @@ def test_graph_json_attr():
     g._set_json_attr('ilist', [1,2,3], 'list_int')
     assert g.json_attr('ilist') == [1,2,3]
 
+def test_order_mutation_pass():
+    x = sym.Variable('x')
+    y = sym.conv2d(data=x, name='conv', dev='gpu')
+    y = sym.add(y, x, name='add1')
+    # write after read
+    z = sym.assign(x, y, name='assign')
+    # read after write
+    t = sym.add(y, x, name='add2')
+    g = graph.create(sym.Group([t, z]))
+    jgraph = json.loads(g.apply(['OrderMutation', 'SaveJSON']).json_attr('json'))
+    jnodes = jgraph['nodes']
+    nindex = {n['name']: i for i, n in enumerate(jnodes)}
+    assert nindex['assign'] in jnodes[nindex['add2']]['control_deps']
+    assert nindex['conv'] in jnodes[nindex['assign']]['control_deps']
+    assert nindex['add1'] in jnodes[nindex['assign']]['control_deps']
+
 
 if __name__ == "__main__":
+    test_order_mutation_pass()
     test_graph_json_attr()
     test_json_pass()
diff --git a/nnvm/tests/python/test_symbol.py b/nnvm/tests/python/test_symbol.py
index 08d24536084d..8259862152ae 100644
--- a/nnvm/tests/python/test_symbol.py
+++ b/nnvm/tests/python/test_symbol.py
@@ -36,8 +36,16 @@ def test_mutate_input():
     except NNVMError:
         pass
 
+def test_copy():
+    x = sym.Variable('x')
+    z = sym.Variable('z')
+    y = sym.exp(sym.add(x, x, name='add', gpu=2),
+                name='exp', gpu=1, attr={"kk": "1"})
+
+    assert y.__copy__().debug_str() == y.debug_str()
 
 if __name__ == "__main__":
+    test_copy()
     test_default_input()
     test_compose()
     test_mutate_input()