diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index 0694509c..401d4d1f 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -5,7 +5,6 @@ cuda_add_library(marian_lib
   cnpy/cnpy.cpp
   exception.cpp
   expression_graph.cu 
-  sgd.cu
   tensor.cu
   tensor_operators.cu
   expression_operators.cu
diff --git a/src/expression_graph.cu b/src/expression_graph.cu
index 00f93621..52a68893 100644
--- a/src/expression_graph.cu
+++ b/src/expression_graph.cu
@@ -39,11 +39,12 @@ std::string Expr::Debug() const
 }
 
 ///////////////////////////////////////////////////////
-ExpressionGraph::ExpressionGraph(int cudaDevice)
-: stack_(new ChainableStack)
-{
-  std::srand (time(NULL));
-  cudaSetDevice(0);
-}
+//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 02ee0117..29d89e65 100644
--- a/src/expression_graph.h
+++ b/src/expression_graph.h
@@ -38,9 +38,14 @@ class Expr {
 
 class ExpressionGraph {
   public:
-    ExpressionGraph(int cudaDevice);
+    ExpressionGraph() : stack_(new ChainableStack) {}
     
-    void forward(size_t batchSize) {
+    void backprop(int batchSize) {
+      forward(batchSize);
+      backward();
+    }
+    
+    void forward(int batchSize) {
       for(auto&& v : *stack_) {
         v->allocate(batchSize);
       }
@@ -48,6 +53,16 @@ class ExpressionGraph {
         v->forward();    
     }
     
+    void backward() {
+      for(auto&& v : *stack_)
+        v->set_zero_adjoint();
+    
+      typedef typename ChainableStack::reverse_iterator It;
+      stack_->back()->init_dependent();
+      for(It it = stack_->rbegin(); it != stack_->rend(); ++it)
+        (*it)->backward();
+    }
+    
     std::string graphviz() {
       std::stringstream ss;
       ss << "digraph ExpressionGraph {" << std::endl;
@@ -60,19 +75,13 @@ class ExpressionGraph {
       return ss.str();
     }
     
-    void backward() {
-      for(auto&& v : *stack_)
-        v->set_zero_adjoint();
-    
-      typedef typename ChainableStack::reverse_iterator It;
-      stack_->back()->init_dependent();
-      for(It it = stack_->rbegin(); it != stack_->rend(); ++it)
-        (*it)->backward();
-    }
+    /*********************************************************/
     
     template <typename ...Args>
     inline Expr input(Args ...args) {
-      return Expr(this, new InputNode(args...));
+      Expr e(this, new InputNode(args...));
+      inputs_.emplace_back(e);
+      return e;
     }
     
     template <typename ...Args>
@@ -117,14 +126,20 @@ class ExpressionGraph {
       named_.emplace(name, e);
     }
     
+    std::vector<Expr>& inputs() {
+      return inputs_;
+    }
+    
     std::vector<Expr>& params() {
       return params_;
     }
     
   private:
     ChainableStackPtr stack_;
+    
     std::map<std::string, Expr> named_;
     std::vector<Expr> params_;
+    std::vector<Expr> inputs_;
 };
 
 }
diff --git a/src/sgd.cu b/src/sgd.cu
deleted file mode 100644
index 598d9f6b..00000000
--- a/src/sgd.cu
+++ /dev/null
@@ -1,140 +0,0 @@
-#include <ctime>
-#include <algorithm>
-#include <vector>
-#include "sgd.h"
-#include "thrust_functions.h"
-
-using namespace std;
-
-namespace marian {
-SGD::SGD(ExpressionGraph& g, float eta,
-    std::vector<float>& xData, size_t numFeatures,
-    std::vector<float>& yData, size_t numClasses,
-    size_t epochs, size_t batchSize)
-: graph_(g),
-  eta_(eta),
-  xData_(xData),
-  numFeatures_(numFeatures),
-  yData_(yData),
-  numClasses_(numClasses),
-  epochs_(epochs),
-  maxBatchSize_(batchSize)
-{}
-
-void SGD::Run()
-{
-  size_t numExamples = xData_.size()/ numFeatures_;
-  Tensor xt({(int)maxBatchSize_, (int)numExamples}, 0.0f);
-  Tensor yt({(int)maxBatchSize_, (int)numClasses_}, 0.0f);
-
-  vector<size_t> shuffle = CreateShuffle(numExamples);
-  //vector<size_t> shuffle;
-
-  for (size_t numEpoch = 0; numEpoch < epochs_; ++numEpoch) {
-    std::cerr << "Starting epoch #" << numEpoch << std::endl;
-    size_t startId = 0;
-
-    while (startId < numExamples) {
-      size_t batchSize = std::min(maxBatchSize_, numExamples - startId);
-      size_t endId = startId + batchSize;
-
-      PrepareBatch(startId, endId, batchSize, shuffle, xt, yt);
-      graph_["x"] = xt;
-      graph_["y"] = yt;
-
-      graph_.forward(maxBatchSize_);
-      graph_.backward();
-
-      UpdateModel();
-
-      startId += maxBatchSize_;
-    }
-  }
-}
-
-std::vector<size_t> SGD::CreateShuffle(size_t numExamples) const {
-  vector<size_t> ret(numExamples);
-  std::iota(ret.begin(), ret.end(), 0);
-  std::random_shuffle ( ret.begin(), ret.end() );
-  /*
-  cerr << "shuffled" << endl;
-  for (size_t i = 0; i < ret.size(); ++i) {
-    cerr << ret[i] << " ";
-  }
-  */
-  return ret;
-}
-
-void SGD::PrepareBatch(
-		size_t startId,
-		size_t endId,
-		size_t batchSize,
-		const std::vector<size_t> &shuffle,
-		Tensor& xt,
-		Tensor& yt) {
-  /*
-  std::vector<float> x(xData_.begin() + startId * numFeatures_,
-                       xData_.begin() + endId * numFeatures_);
-  std::vector<float> y(yData_.begin() + startId * numClasses_,
-                       yData_.begin() + endId * numClasses_);
-  */
-  std::vector<float> x(batchSize * numFeatures_);
-  std::vector<float> y(batchSize * numClasses_);
-  
-  //cerr << "batchSize=" << batchSize << endl;
-  /*
-  cerr << "startId=" << startId
-       << " " << endId
-       << " " << batchSize
-       << endl;
-  cerr << "numExamples=" << shuffle.size() << endl;
-  cerr << "numFeatures_=" << numFeatures_ << " " << numClasses_ << endl;
-  cerr << "sizes=" << x.size() 
-       << " " << y.size() 
-       << " " << xData_.size()
-       << " " << yData_.size()
-       << endl;
-  */
-  size_t startXId = 0;
-  size_t startYId = 0;
-  
-  for (size_t i = startId; i < endId; ++i) {
-    size_t ind = shuffle[i];
-    size_t startXDataId = ind * numFeatures_;
-    size_t startYDataId = ind * numClasses_;
-
-    size_t endXDataId = startXDataId + numFeatures_;
-    size_t endYDataId = startYDataId + numClasses_;
-    /*
-    cerr << "i=" << i
-    	 << " " << ind
-    	 << " " << startXDataId << "-" << endXDataId
-	 << " " << startYDataId << "-" << endYDataId
-	 << endl;
-    */
-
-    std::copy(xData_.begin() + startXDataId,
-        xData_.begin() + endXDataId,
-        x.begin() + startXId);
-
-    std::copy(yData_.begin() + startYDataId,
-        yData_.begin() + endYDataId,
-        y.begin() + startYId);
-
-    startXId += numFeatures_;
-    startYId += numClasses_;
-  }
-  
-  xt.set(x);
-  yt.set(y);
-}
-
-void SGD::UpdateModel() {
-  for (auto& param : graph_.params()) {
-    using namespace thrust::placeholders;
-    Element(_1 -= eta_ * _2, param.val(), param.grad());
-  }
-}
-
-} // namespace
-
diff --git a/src/sgd.h b/src/sgd.h
index a99acd75..7d3f3200 100644
--- a/src/sgd.h
+++ b/src/sgd.h
@@ -1,43 +1,48 @@
 #pragma once
 
-#include <memory>
-#include <iostream>
-
-#include "expression_graph.h"
-#include "thrust_functions.h"
+#include <map>
+#include <boost/any.hpp>
 #include "tensor_operators.h"
 
 namespace marian {
 
-class SGD {
+class Sgd {
   public:
-    SGD(ExpressionGraph& g, float eta,
-        std::vector<float>& xData, size_t numFeatures,
-        std::vector<float>& yData, size_t numClasses,
-        size_t epochs, size_t batchSize);
-
-    void Run();
-
+    Sgd(float eta=0.1) : eta_(eta) {}
+    
+    void operator()(ExpressionGraph& graph, int batchSize) {
+      graph.backprop(batchSize);
+      
+      for(auto& param : graph.params())
+        Element(_1 -= eta_ * _2, param.val(), param.grad());
+    }
+    
   private:
-    ExpressionGraph& graph_;
-    const float eta_;
-    std::vector<float>& xData_;
-    const size_t numFeatures_;
-    std::vector<float>& yData_;
-    const size_t numClasses_;
-    const size_t epochs_;
-    const size_t maxBatchSize_;
-
-    std::vector<size_t> CreateShuffle(size_t numExamples) const;
-    void PrepareBatch(
-    		size_t startId,
-    		size_t endId,
-    		size_t batchSize,
-    		const std::vector<size_t> &shuffle,
-    		Tensor& xt,
-    		Tensor& yt);
-
-    void UpdateModel();
+    float eta_;
 };
 
-} // namespace marian
+class Adagrad {
+  public:
+    Adagrad(float eta=0.1) : eta_(eta) {}
+    
+    void operator()(ExpressionGraph& graph, int batchSize) {
+      if(history_.size() < graph.params().size())
+        for(auto& param : graph.params())
+          history_.emplace_back(Tensor(param.grad().shape(), 0));
+      
+      graph.backprop(batchSize);
+      
+      auto it = history_.begin();
+      for(auto& param : graph.params()) {    
+        Element(_1 -= eta_ / Sqrt(_2) * _3, param.val(), *it, param.grad());
+        Element(_1 += _2 * _2, *it, param.grad());
+        it++;
+      }
+    }
+    
+  private:
+    float eta_;
+    std::vector<Tensor> history_;
+};
+
+}
\ No newline at end of file
diff --git a/src/tensor.cu b/src/tensor.cu
index 0c3e8a3e..3ec4e71e 100644
--- a/src/tensor.cu
+++ b/src/tensor.cu
@@ -1,8 +1,6 @@
 #include <fstream>
 #include "tensor.h"
 
-using namespace std;
-
 namespace marian {
 
 void Tensor::set(const std::vector<float>& data)
diff --git a/src/test.cu b/src/test.cu
index 5b128976..7322664e 100644
--- a/src/test.cu
+++ b/src/test.cu
@@ -65,7 +65,7 @@ int main(int argc, char** argv) {
   std::vector<Expr> Y;
   std::vector<Expr> H;
 
-  ExpressionGraph g(0);
+  ExpressionGraph g;
 
   for (int t = 0; t < num_inputs; ++t) {
     X.emplace_back(g.input(shape={batch_size, input_size}));
@@ -83,10 +83,9 @@ int main(int argc, char** argv) {
 
   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);
+    getline(targetFile, targetLine);
+    std::vector<size_t> sourceIds = sourceVocab.ProcessSentence(sourceLine);
+    std::vector<size_t> targetIds = sourceVocab.ProcessSentence(targetLine);
   }
 
   std::cerr << "Building RNN..." << std::endl;
diff --git a/src/thrust_functions.h b/src/thrust_functions.h
index 2712fda7..1ab99473 100644
--- a/src/thrust_functions.h
+++ b/src/thrust_functions.h
@@ -85,6 +85,19 @@ namespace thrust
         return compose(unary_operator<unary_tanh>(), _1);
       }
       
+      template<typename T>
+      struct unary_sqrt : public thrust::unary_function<T,T> {
+        __host__ __device__
+        T operator()(const T &x) const { return sqrtf(x); }
+      };
+      
+      template<typename Eval>
+      __host__ __device__
+      actor<composite<unary_operator<unary_sqrt>, actor<Eval>>>
+      Sqrt(const actor<Eval> &_1) {
+        return compose(unary_operator<unary_sqrt>(), _1);
+      }
+      
       template<typename T1, typename T2>
       __host__ __device__
       actor<composite<binary_operator<thrust::maximum>, actor<T1>, actor<T2>>>
diff --git a/src/train_mnist.cu b/src/train_mnist.cu
index 09e08d15..2dda8fde 100644
--- a/src/train_mnist.cu
+++ b/src/train_mnist.cu
@@ -11,12 +11,12 @@ int main(int argc, char** argv) {
   int numofdata;
 
   vector<float> trainImages = datasets::mnist::ReadImages("../examples/mnist/t10k-images-idx3-ubyte", numofdata, IMAGE_SIZE);
-  vector<float>trainLabels = datasets::mnist::ReadLabels("../examples/mnist/t10k-labels-idx1-ubyte", numofdata, LABEL_SIZE);
+  vector<float> trainLabels = datasets::mnist::ReadLabels("../examples/mnist/t10k-labels-idx1-ubyte", numofdata, LABEL_SIZE);
 
   using namespace marian;
   using namespace keywords;
 
-  ExpressionGraph g(0);
+  ExpressionGraph g;
   
   Expr x = named(g.input(shape={whatevs, IMAGE_SIZE}), "x");
   Expr y = named(g.input(shape={whatevs, LABEL_SIZE}), "y");
@@ -24,16 +24,13 @@ int main(int argc, char** argv) {
   Expr w = named(g.param(shape={IMAGE_SIZE, LABEL_SIZE}), "w");
   Expr b = named(g.param(shape={1, LABEL_SIZE}), "b");
 
-  std::vector<Expr*> params;
-  params.push_back(&w);
-  params.push_back(&b);
-
   auto scores = dot(x, w) + b;
   auto lr = softmax_fast(scores);
   auto cost = named(-mean(sum(y * log(lr), axis=1), axis=0), "cost");
   cerr << "lr=" << lr.Debug() << endl;
 
-  SGD opt(g, 0.9, trainImages, IMAGE_SIZE, trainLabels, LABEL_SIZE, 3, 24);
-  opt.Run();
+  Adagrad opt;
+  opt(g, 300);
+  
   return 0;
 }
diff --git a/src/validate_encoder_decoder.cu b/src/validate_encoder_decoder.cu
index 1df1a897..d1f54bde 100644
--- a/src/validate_encoder_decoder.cu
+++ b/src/validate_encoder_decoder.cu
@@ -15,10 +15,10 @@ const int batch_size = 25;
 const int num_inputs = 8;
 const int num_outputs = 6;
 
-ExpressionGraph build_graph(int cuda_device) {
+ExpressionGraph build_graph() {
   std::cerr << "Building computation graph..." << std::endl;
 
-  ExpressionGraph g(cuda_device);
+  ExpressionGraph g;
   std::vector<Expr> X, Y, H, S;
 
   // We're including the stop symbol here.
@@ -119,7 +119,7 @@ int main(int argc, char** argv) {
 #endif
 
   // Build the encoder-decoder computation graph.
-  ExpressionGraph g = build_graph(0);
+  ExpressionGraph g = build_graph();
 
   // Generate input data (include the stop symbol).
   for (int t = 0; t <= num_inputs; ++t) {
diff --git a/src/validate_mnist.cu b/src/validate_mnist.cu
index 01fb4c50..f9bc0dcf 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(int cudaDevice) {
+ExpressionGraph build_graph() {
   std::cerr << "Loading model params...";
   NpzConverter converter("../scripts/test_model_single/model.npz");
 
@@ -22,7 +22,7 @@ ExpressionGraph build_graph(int cudaDevice) {
 
   std::cerr << "Building model...";
   
-  ExpressionGraph g(cudaDevice);
+  ExpressionGraph g;
   auto x = named(g.input(shape={whatevs, IMAGE_SIZE}), "x");
   auto y = named(g.input(shape={whatevs, LABEL_SIZE}), "y");
   
@@ -52,7 +52,7 @@ int main(int argc, char** argv) {
   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(0);
+  ExpressionGraph g = build_graph();
   
   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 754d254c..d37e9ca3 100644
--- a/src/validate_mnist_batch.cu
+++ b/src/validate_mnist_batch.cu
@@ -56,8 +56,7 @@ int main(int argc, char** argv) {
 
   std::cerr << "\tDone." << std::endl;
 
-
-  ExpressionGraph g(0);
+  ExpressionGraph g;
 
   auto x = g.input(shape={whatevs, IMAGE_SIZE}, name="X");
   auto y = g.input(shape={whatevs, LABEL_SIZE}, name="Y");