diff --git a/src/chainable.h b/src/chainable.h
index 885efdbd..a1683966 100644
--- a/src/chainable.h
+++ b/src/chainable.h
@@ -18,7 +18,7 @@ struct Chainable {
 
     virtual void allocate(size_t) = 0;
     virtual std::string graphviz() = 0;
-
+    virtual const std::string &name() const = 0;
     
     virtual const Shape& shape() = 0;
     virtual DataType &val() = 0;
@@ -33,4 +33,4 @@ typedef std::shared_ptr<ChainableStack> ChainableStackPtr;
 typedef std::shared_ptr<Chainable<Tensor>> ChainPtr;
 
 
-}
\ No newline at end of file
+}
diff --git a/src/expression_graph.cu b/src/expression_graph.cu
index 61f8d2b5..22de1c89 100644
--- a/src/expression_graph.cu
+++ b/src/expression_graph.cu
@@ -37,5 +37,14 @@ std::string Expr::Debug() const
 	strm << marian::Debug(shape);
 	return strm.str();
 }
-    
+
+///////////////////////////////////////////////////////
+ExpressionGraph::ExpressionGraph(int cudaDevice)
+: stack_(new ChainableStack)
+{
+  std::srand (time(NULL));
+  cudaSetDevice(0);
+
+}
+
 }
diff --git a/src/expression_graph.h b/src/expression_graph.h
index 7a766679..02ee0117 100644
--- a/src/expression_graph.h
+++ b/src/expression_graph.h
@@ -38,9 +38,7 @@ class Expr {
 
 class ExpressionGraph {
   public:
-    ExpressionGraph()
-    : stack_(new ChainableStack)
-    {}
+    ExpressionGraph(int cudaDevice);
     
     void forward(size_t batchSize) {
       for(auto&& v : *stack_) {
@@ -54,10 +52,10 @@ class ExpressionGraph {
       std::stringstream ss;
       ss << "digraph ExpressionGraph {" << std::endl;
       ss << "rankdir=BT" << std::endl;
-      
       typedef typename ChainableStack::reverse_iterator It;
-      for(It it = stack_->rbegin(); it != stack_->rend(); ++it)
+      for(It it = stack_->rbegin(); it != stack_->rend(); ++it) {
         ss << (*it)->graphviz();
+      }
       ss << "}" << std::endl;
       return ss.str();
     }
diff --git a/src/node.h b/src/node.h
index 29d240cd..dfdaca00 100644
--- a/src/node.h
+++ b/src/node.h
@@ -67,6 +67,8 @@ class Node : public Chainable<Tensor>,
     virtual const Shape& shape() {
       return shape_;    
     }
+
+    const std::string &name() const { return name_; }
     
   protected:
     Shape shape_;
diff --git a/src/sgd.cu b/src/sgd.cu
index 5fe69138..598d9f6b 100644
--- a/src/sgd.cu
+++ b/src/sgd.cu
@@ -23,8 +23,6 @@ SGD::SGD(ExpressionGraph& g, float eta,
 
 void SGD::Run()
 {
-  std::srand ( unsigned ( std::time(0) ) );
-
   size_t numExamples = xData_.size()/ numFeatures_;
   Tensor xt({(int)maxBatchSize_, (int)numExamples}, 0.0f);
   Tensor yt({(int)maxBatchSize_, (int)numClasses_}, 0.0f);
diff --git a/src/test.cu b/src/test.cu
index 70b50007..8d7073f4 100644
--- a/src/test.cu
+++ b/src/test.cu
@@ -4,7 +4,6 @@
 #include "vocab.h"
 
 int main(int argc, char** argv) {
-  cudaSetDevice(0);
 
   using namespace std;
   using namespace marian;
@@ -22,7 +21,7 @@ int main(int argc, char** argv) {
   std::vector<Expr> Y;
   std::vector<Expr> H;
 
-  ExpressionGraph g;
+  ExpressionGraph g(0);
 
   for (int t = 0; t < num_inputs; ++t) {
     X.emplace_back(g.input(shape={batch_size, input_size}));
diff --git a/src/train_mnist.cu b/src/train_mnist.cu
index 64ccf564..09e08d15 100644
--- a/src/train_mnist.cu
+++ b/src/train_mnist.cu
@@ -16,7 +16,7 @@ int main(int argc, char** argv) {
   using namespace marian;
   using namespace keywords;
 
-  ExpressionGraph g;
+  ExpressionGraph g(0);
   
   Expr x = named(g.input(shape={whatevs, IMAGE_SIZE}), "x");
   Expr y = named(g.input(shape={whatevs, LABEL_SIZE}), "y");
diff --git a/src/validate_encoder_decoder.cu b/src/validate_encoder_decoder.cu
index d8eea261..ded9982e 100644
--- a/src/validate_encoder_decoder.cu
+++ b/src/validate_encoder_decoder.cu
@@ -1,6 +1,8 @@
 
 #include "marian.h"
 #include "mnist.h"
+#include "vocab.h"
+#include <assert.h>
 
 using namespace marian;
 using namespace keywords;
@@ -32,10 +34,10 @@ ExpressionGraph build_graph(int cuda_device) {
     Y.emplace_back(named(g.input(shape={batch_size, output_size}), ss.str()));
   }
 
-  Expr Wxh = g.param(shape={input_size, hidden_size}, init=uniform(), name="Wxh");
-  Expr Whh = g.param(shape={hidden_size, hidden_size}, init=uniform(), name="Whh");
-  Expr bh = g.param(shape={1, hidden_size}, init=uniform(), name="bh");
-  Expr h0 = g.param(shape={1, hidden_size}, init=uniform(), name="h0");
+  Expr Wxh = named(g.param(shape={input_size, hidden_size}, init=uniform()), "Wxh");
+  Expr Whh = named(g.param(shape={hidden_size, hidden_size}, init=uniform()), "Whh");
+  Expr bh = named(g.param(shape={1, hidden_size}, init=uniform()), "bh");
+  Expr h0 = named(g.param(shape={1, hidden_size}, init=uniform()), "h0");
 
   std::cerr << "Building encoder RNN..." << std::endl;
   H.emplace_back(tanh(dot(X[0], Wxh) + dot(h0, Whh) + bh));
@@ -43,9 +45,9 @@ ExpressionGraph build_graph(int cuda_device) {
     H.emplace_back(tanh(dot(X[t], Wxh) + dot(H[t-1], Whh) + bh));
   }
 
-  Expr Wxh_d = g.param(shape={output_size, hidden_size}, init=uniform(), name="Wxh_d");
-  Expr Whh_d = g.param(shape={hidden_size, hidden_size}, init=uniform(), name="Whh_d");
-  Expr bh_d = g.param(shape={1, hidden_size}, init=uniform(), name="bh_d");
+  Expr Wxh_d = named(g.param(shape={output_size, hidden_size}, init=uniform()), "Wxh_d");
+  Expr Whh_d = named(g.param(shape={hidden_size, hidden_size}, init=uniform()), "Whh_d");
+  Expr bh_d = named(g.param(shape={1, hidden_size}, init=uniform()), "bh_d");
 
   std::cerr << "Building decoder RNN..." << std::endl;
   auto h0_d = H[num_inputs];
@@ -54,8 +56,8 @@ ExpressionGraph build_graph(int cuda_device) {
     S.emplace_back(tanh(dot(Y[t], Wxh_d) + dot(S[t-1], Whh_d) + bh_d));
   }
 
-  Expr Why = g.param(shape={hidden_size, output_size}, init=uniform(), name="Why");
-  Expr by = g.param(shape={1, output_size}, init=uniform(), name="by");
+  Expr Why = named(g.param(shape={hidden_size, output_size}, init=uniform()), "Why");
+  Expr by = named(g.param(shape={1, output_size}, init=uniform()), "by");
 
   std::cerr << "Building output layer..." << std::endl;
   std::vector<Expr> Yp;
@@ -66,29 +68,40 @@ ExpressionGraph build_graph(int cuda_device) {
     Yp.emplace_back(named(softmax_fast(dot(S[t-1], Why) + by), "pred"));
     cross_entropy = cross_entropy + sum(Y[t] * log(Yp[t]), axis=1);
   }
-  auto graph = -mean(cross_entropy, axis=0, name="cost");
+  auto cost = named(-mean(cross_entropy, axis=0), "cost");
 
   std::cerr << "Done." << std::endl;
 
   return g;
 }
 
-#if 0
+
+
+int main(int argc, char** argv) {
+#if 1
+  std::cerr << "Loading the data... ";
+  Vocab sourceVocab, targetVocab;
+
   // read parallel corpus from file
   std::fstream sourceFile("../examples/mt/dev/newstest2013.de");
   std::fstream targetFile("../examples/mt/dev/newstest2013.en");
 
+  std::vector<std::vector<size_t> > source_sentences, target_sentences;
   std::string sourceLine, targetLine;
   while (getline(sourceFile, sourceLine)) {
     getline(targetFile, targetLine);
     std::vector<size_t> sourceIds = sourceVocab.ProcessSentence(sourceLine);
-    std::vector<size_t> targetIds = sourceVocab.ProcessSentence(targetLine);
+    std::vector<size_t> targetIds = targetVocab.ProcessSentence(targetLine);
+    source_sentences.push_back(sourceIds);
+    target_sentences.push_back(targetIds);
   }
+  std::cerr << "Done." << std::endl;
+  std::cerr << source_sentences.size()
+            << " sentence pairs read." << std::endl;
+  std::cerr << "Source vocabulary size: " << sourceVocab.Size() << std::endl;
+  std::cerr << "Target vocabulary size: " << targetVocab.Size() << std::endl;
 #endif
 
-
-int main(int argc, char** argv) {
-
   ExpressionGraph g = build_graph(0);
 
   // For the stop symbol.
@@ -109,6 +122,7 @@ int main(int argc, char** argv) {
 
     std::stringstream ss;
     ss << "X" << t;
+    if (!g.has_node(ss.str())) std::cerr << "No node " << ss.str() << "!!!" << std::endl;
     g[ss.str()] = Xt;
 
   }
@@ -128,6 +142,7 @@ int main(int argc, char** argv) {
 
     std::stringstream ss;
     ss << "Y" << t;
+    if (!g.has_node(ss.str())) std::cerr << "No node " << ss.str() << "!!!" << std::endl;
     g[ss.str()] = Yt;
   }
 
@@ -140,18 +155,18 @@ int main(int argc, char** argv) {
   g.backward();
   std::cerr << "Done" << std::endl;
 
-  std::cerr << g["graph"].val().Debug() << std::endl;
+  std::cerr << g["cost"].val().Debug() << std::endl;
 
   std::cerr << g["X0"].val().Debug() << std::endl;
   std::cerr << g["Y0"].val().Debug() << std::endl;
 
-#if 0
-  std::cerr << Whh.grad().Debug() << std::endl;
-  std::cerr << bh.grad().Debug() << std::endl;
-  std::cerr << Why.grad().Debug() << std::endl;
-  std::cerr << by.grad().Debug() << std::endl;
-  std::cerr << Wxh.grad().Debug() << std::endl;
-  std::cerr << h0.grad().Debug() << std::endl;
+#if 1
+  std::cerr << g["Whh"].grad().Debug() << std::endl;
+  std::cerr << g["bh"].grad().Debug() << std::endl;
+  std::cerr << g["Why"].grad().Debug() << std::endl;
+  std::cerr << g["by"].grad().Debug() << std::endl;
+  std::cerr << g["Wxh"].grad().Debug() << std::endl;
+  std::cerr << g["h0"].grad().Debug() << std::endl;
 #endif
 
   return 0;
diff --git a/src/validate_mnist.cu b/src/validate_mnist.cu
index f71be921..01fb4c50 100644
--- a/src/validate_mnist.cu
+++ b/src/validate_mnist.cu
@@ -10,7 +10,7 @@ const size_t IMAGE_SIZE = 784;
 const size_t LABEL_SIZE = 10;
 int BATCH_SIZE = 10000;
 
-ExpressionGraph build_graph() {
+ExpressionGraph build_graph(int cudaDevice) {
   std::cerr << "Loading model params...";
   NpzConverter converter("../scripts/test_model_single/model.npz");
 
@@ -22,7 +22,7 @@ ExpressionGraph build_graph() {
 
   std::cerr << "Building model...";
   
-  ExpressionGraph g;
+  ExpressionGraph g(cudaDevice);
   auto x = named(g.input(shape={whatevs, IMAGE_SIZE}), "x");
   auto y = named(g.input(shape={whatevs, LABEL_SIZE}), "y");
   
@@ -46,15 +46,13 @@ ExpressionGraph build_graph() {
 }
 
 int main(int argc, char** argv) {
-  
-  cudaSetDevice(0);
-    
+
   std::cerr << "Loading test set...";
   std::vector<float> testImages = datasets::mnist::ReadImages("../examples/mnist/t10k-images-idx3-ubyte", BATCH_SIZE, IMAGE_SIZE);
   std::vector<float> testLabels = datasets::mnist::ReadLabels("../examples/mnist/t10k-labels-idx1-ubyte", BATCH_SIZE, LABEL_SIZE);
   std::cerr << "Done." << std::endl;
 
-  ExpressionGraph g = build_graph();
+  ExpressionGraph g = build_graph(0);
   
   Tensor xt({BATCH_SIZE, IMAGE_SIZE});
   Tensor yt({BATCH_SIZE, LABEL_SIZE});
diff --git a/src/validate_mnist_batch.cu b/src/validate_mnist_batch.cu
index 50ab97b5..754d254c 100644
--- a/src/validate_mnist_batch.cu
+++ b/src/validate_mnist_batch.cu
@@ -7,9 +7,7 @@ using namespace marian;
 using namespace keywords;
 
 int main(int argc, char** argv) {
-  
-  cudaSetDevice(0);
-  
+
   const size_t IMAGE_SIZE = 784;
   const size_t LABEL_SIZE = 10;
   const size_t BATCH_SIZE = 24;
@@ -59,7 +57,7 @@ int main(int argc, char** argv) {
   std::cerr << "\tDone." << std::endl;
 
 
-  ExpressionGraph g;
+  ExpressionGraph g(0);
 
   auto x = g.input(shape={whatevs, IMAGE_SIZE}, name="X");
   auto y = g.input(shape={whatevs, LABEL_SIZE}, name="Y");
diff --git a/src/vocab.cpp b/src/vocab.cpp
index 705c21b2..25c28386 100644
--- a/src/vocab.cpp
+++ b/src/vocab.cpp
@@ -1,3 +1,4 @@
+#include <limits>
 #include "vocab.h"
 
 using namespace std;
@@ -23,7 +24,6 @@ inline std::vector<std::string> Tokenize(const std::string& str,
 
   return tokens;
 }
-////////////////////////////////////////////////////////
 
 size_t Vocab::GetOrCreate(const std::string &word)
 {
@@ -39,6 +39,12 @@ size_t Vocab::GetOrCreate(const std::string &word)
 	return id;
 }
 
+size_t Vocab::Get(const std::string &word) const
+{
+	Coll::const_iterator iter = coll_.find(word);
+	return iter->second;
+}
+
 std::vector<size_t> Vocab::ProcessSentence(const std::string &sentence)
 {
 	vector<string> toks = Tokenize(sentence);
diff --git a/src/vocab.h b/src/vocab.h
index 5e055511..3127083d 100644
--- a/src/vocab.h
+++ b/src/vocab.h
@@ -7,9 +7,22 @@
 class Vocab
 {
 public:
-	size_t GetOrCreate(const std::string &word);
+  Vocab() {
+    GetOrCreate("__UNK__");
+    GetOrCreate("__PAD__");
+    GetOrCreate("__EOS__");
+  }
+  virtual ~Vocab() {}
+
+public:
+        size_t Size() const { return coll_.size(); }
+        size_t Get(const std::string &word) const;
+        size_t GetOrCreate(const std::string &word);
 	std::vector<size_t> ProcessSentence(const std::string &sentence);
 
+	size_t GetUNK() const { return Get("__UNK__"); }
+	size_t GetPAD() const { return Get("__PAD__"); }
+	size_t GetEOS() const { return Get("__EOS__"); }
 protected:
 	typedef std::unordered_map<std::string, size_t> Coll;
 	Coll coll_;