diff --git a/source/AStack.cpp b/source/AStack.cpp
index 67a2992..e824534 100644
--- a/source/AStack.cpp
+++ b/source/AStack.cpp
@@ -26,6 +26,7 @@ AStack::AStack(StackType type, const std::string &name)
 : m_name(name)
 , m_type(type)
 , m_pLayers(nullptr)
+, m_numLayers(0)
 {
 }
 
@@ -50,16 +51,9 @@ void AStack::setName(const std::string& name)
 	m_name = name;
 }
 
-size_t AStack::numLayers()
+size_t AStack::numLayers() const
 {
-	size_t count = 0;
-	Layer *pLayer = m_pLayers;
-	while(pLayer)
-	{
-		count++;
-		pLayer = pLayer->next;
-	}
-	return count;
+	return m_numLayers;
 }
 
 void AStack::addLayer(Layer *pOtherLayer)
@@ -79,6 +73,7 @@ void AStack::addLayer(Layer *pOtherLayer)
 		pLayer->next = pOtherLayer;
 		pOtherLayer->prev = pLayer;
 	}
+	updateNumLayers();
 }
 
 void AStack::delLayer(Layer* pLayer)
@@ -86,6 +81,17 @@ void AStack::delLayer(Layer* pLayer)
 	assert(!"Stack::delLayer: Not implemented!");
 }
 
+void AStack::updateNumLayers()
+{
+	m_numLayers = 0;
+	Layer *pLayer = m_pLayers;
+	while(pLayer)
+	{
+		m_numLayers++;
+		pLayer = pLayer->next;
+	}
+}
+
 Layer* AStack::getLayer(size_t layerId) const
 {
 	Layer *pLayer = m_pLayers;
@@ -101,6 +107,16 @@ Layer* AStack::getLayer(size_t layerId) const
 	
 }
 
+Layer* AStack::getFirstLayer() const
+{
+	return getLayer(0);
+}
+
+Layer* AStack::getLastLayer() const
+{
+	return getLayer(numLayers()-1);
+}
+
 bool AStack::save(const std::string &dir)
 {
 	return StackCreator::toFile(this, dir, m_name);
diff --git a/source/AStack.hpp b/source/AStack.hpp
index a09d01f..20cd476 100644
--- a/source/AStack.hpp
+++ b/source/AStack.hpp
@@ -53,7 +53,7 @@ public:
 	
 	StackType type();
 	void setName(const std::string &name);
-	size_t numLayers();
+	size_t numLayers() const;
 	virtual size_t numContext()
 	{
 		return 0;
@@ -62,6 +62,8 @@ public:
 	void delLayer(Layer *pLayer);
 	
 	Layer* getLayer(size_t layerId) const;
+	Layer* getFirstLayer() const;
+	Layer* getLastLayer() const;
 
 	bool save(const std::string &dir);
 
@@ -85,6 +87,8 @@ protected:
 
 private:
 	arma::mat m_trainingBatch;
+	size_t m_numLayers;
+	void updateNumLayers();
 	
 };
 
diff --git a/source/DeepStack.cpp b/source/DeepStack.cpp
index 40a63f9..8603d59 100644
--- a/source/DeepStack.cpp
+++ b/source/DeepStack.cpp
@@ -24,18 +24,18 @@ DeepStack::~DeepStack()
 { 
 }
 
-arma::mat DeepStack::trainingBatchFrom(size_t layerId, const arma::mat& batch)
+arma::mat DeepStack::trainingBatchFrom(Layer *pLayer, const arma::mat& batch)
 {
 	arma::mat thisBatch = batch;
-	Layer *pLayer = getLayer(0);
-	while (pLayer)
+	Layer *pLayerForward = getFirstLayer();
+	while (pLayerForward)
 	{
-		if (pLayer->id() == layerId)
+		if (pLayerForward == pLayer)
 		{
 			break;
 		}
-		thisBatch = pLayer->toHiddenProbs(thisBatch);
-		pLayer = pLayer->next;
+		thisBatch = pLayerForward->toHiddenProbs(thisBatch);
+		pLayerForward = pLayerForward->next;
 	}
 	return thisBatch;
 }
@@ -43,48 +43,21 @@ arma::mat DeepStack::trainingBatchFrom(size_t layerId, const arma::mat& batch)
 void DeepStack::train(const arma::mat& batch, Rbm::IListener* pListener)
 {
 	arma::mat thisBatch = batch;
-	Layer *pLayer = getLayer(0);
+	Layer *pLayer = getFirstLayer();
 	while (pLayer)
 	{
-		thisBatch = trainingBatchFrom(pLayer->id(), thisBatch);
+		thisBatch = trainingBatchFrom(pLayer, thisBatch);
 		pLayer->train(thisBatch, pListener);
 		pLayer = pLayer->next;
 	}
 }
 
-void DeepStack::train(size_t layerId, const arma::mat& batch, Rbm::IListener* pListener)
+void DeepStack::train(Layer *pLayer, const arma::mat& batch, Rbm::IListener* pListener)
 {
-	arma::mat thisBatch = batch;
-	Layer *pLayer = getLayer(0);
-	while (pLayer)
-	{
-		if (pLayer->id() == layerId)
-		{
-			break;
-		}
-		thisBatch = pLayer->toHiddenProbs(thisBatch);
-		pLayer = pLayer->next;
-	}
+	arma::mat thisBatch = trainingBatchFrom(pLayer, batch);
 	pLayer->train(thisBatch, pListener);
 }
 
-arma::mat DeepStack::upPass(size_t layerId, const arma::mat& v)
-{
-	return upPass(getLayer(layerId), v);
-}
-
-arma::mat DeepStack::downPass(size_t layerId, const arma::mat& h)
-{
-	return downPass(getLayer(layerId), h);
-}
-
-arma::mat DeepStack::upDownPass(size_t layerId, const arma::mat& v)
-{
-	arma::mat h = upPass(layerId, v);
-	arma::mat r = downPass(numLayers()-1, h);
-	return r;
-}
-
 arma::mat DeepStack::upPass(Layer *pLayer, arma::mat const &v)
 {
 	arma::mat h = v;
@@ -112,3 +85,11 @@ arma::mat DeepStack::downPass(Layer *pLayer, arma::mat const &h)
 	}
 	return v;
 }
+
+arma::mat DeepStack::upDownPass(Layer *pLayer, const arma::mat& v)
+{
+	arma::mat h = upPass(pLayer, v);
+	arma::mat r = downPass(getLastLayer(), h);
+	return r;
+}
+
diff --git a/source/DeepStack.hpp b/source/DeepStack.hpp
index e993574..2c7584d 100644
--- a/source/DeepStack.hpp
+++ b/source/DeepStack.hpp
@@ -29,16 +29,13 @@ public:
 	virtual ~DeepStack();
 	
 	void train(const arma::mat& batch, Rbm::IListener* pListener) override;
-	arma::mat trainingBatchFrom(size_t layerId, const arma::mat& batch);
-	void train(size_t layerId, const arma::mat& batch, Rbm::IListener* pListener);
-	
-    arma::mat upPass(size_t layerId, arma::mat const &v);
-    arma::mat downPass(size_t layerId, arma::mat const &h);
-    arma::mat upDownPass(size_t layerId, arma::mat const &v);
+	void train(Layer *pLayer, const arma::mat& batch, Rbm::IListener* pListener);
+
+	arma::mat trainingBatchFrom(Layer *pLayer, const arma::mat& batch);
 
     arma::mat upPass(Layer *pLayer, arma::mat const &v);
+	arma::mat upDownPass(Layer *pLayer, const arma::mat& v);
     arma::mat downPass(Layer *pLayer, arma::mat const &h);
-
 };
 
 
diff --git a/source/Layer.cpp b/source/Layer.cpp
index 7a5af64..9086673 100644
--- a/source/Layer.cpp
+++ b/source/Layer.cpp
@@ -89,7 +89,7 @@ Layer* Layer::root()
 	return pLayer;
 }
 
-arma::mat Layer::to_h_gibbs(const arma::mat& v_probs)
+arma::mat Layer::to_h_gibbs(const arma::mat& v_probs) const
 {
 	onUpPass(v_probs);
 
@@ -99,7 +99,7 @@ arma::mat Layer::to_h_gibbs(const arma::mat& v_probs)
 	return h;
 }
 
-arma::mat Layer::to_v_gibbs(const arma::mat& h_probs)
+arma::mat Layer::to_v_gibbs(const arma::mat& h_probs) const
 {
 	onDownPass(h_probs);
 
diff --git a/source/Layer.hpp b/source/Layer.hpp
index 8c78e6b..2aef01e 100644
--- a/source/Layer.hpp
+++ b/source/Layer.hpp
@@ -51,8 +51,8 @@ public:
 	void calcContextBatch(arma::mat &batch);
 	void train(arma::mat const &batch, IListener *pListener=nullptr);
 	
-	arma::mat to_h_gibbs(const arma::mat& v_probs);
-	arma::mat to_v_gibbs(const arma::mat& h_probs);
+	arma::mat to_h_gibbs(const arma::mat& v_probs) const;
+	arma::mat to_v_gibbs(const arma::mat& h_probs) const;
 
 private:
 	
@@ -67,8 +67,8 @@ protected:
     size_t m_numVisibleY;
     size_t m_numContext;
 
-	virtual void onUpPass(const arma::mat& v) {}
-	virtual void onDownPass(const arma::mat& h) {}
+	virtual void onUpPass(const arma::mat& v)const {}
+	virtual void onDownPass(const arma::mat& h) const {}
 
 };
 
diff --git a/source/MainComponent.cpp b/source/MainComponent.cpp
index 10542ca..db7cc5a 100644
--- a/source/MainComponent.cpp
+++ b/source/MainComponent.cpp
@@ -685,8 +685,13 @@ void MainComponent::sliderValueChanged (Slider* sliderThatWasMoved)
     if (sliderThatWasMoved == patterSlider)
     {
         //[UserSliderCode_patterSlider] -- add your slider handling code here..
-		m_trainingIndex = (int)sliderThatWasMoved->getValue();
-		m_stack->upDownPass(m_pLayer->id(), m_stack->trainingBatchFrom(m_pLayer->id(), trainingAt(m_trainingIndex)));
+
+		size_t trainingIndex = (size_t)sliderThatWasMoved->getValue();
+        if (trainingIndex < m_stack->numTraining())
+        {
+            m_trainingIndex = trainingIndex;
+    		m_stack->upDownPass(m_pLayer, m_stack->trainingBatchFrom(m_pLayer, trainingAt(m_trainingIndex)));
+        }
         //[/UserSliderCode_patterSlider]
     }
     else if (sliderThatWasMoved == WeightsSlider)
@@ -822,7 +827,7 @@ void MainComponent::comboBoxChanged (ComboBox* comboBoxThatHasChanged)
 		m_pLayer->redrawWeights(m_weightIndex);
 		if (m_stack->trainingBatch().n_rows > 0)
 		{
-			m_stack->upDownPass(index, m_stack->trainingBatchFrom(index, trainingAt(m_trainingIndex)));
+			m_stack->upDownPass(m_pLayer, m_stack->trainingBatchFrom(m_pLayer, trainingAt(m_trainingIndex)));
 		}
         //[/UserComboBoxCode_m_rbmSelect]
     }
@@ -906,7 +911,7 @@ void MainComponent::run()
 {
     trainButton->setButtonText (TRANS("Stop"));
 	m_pLayer->calcContextBatch(m_stack->trainingBatch());
-	m_stack->train(m_pLayer->id(), m_stack->trainingBatch(), this);
+	m_stack->train(m_pLayer, m_stack->trainingBatch(), this);
     trainButton->setButtonText (TRANS("Train"));
 }
 
@@ -922,7 +927,7 @@ bool MainComponent::onProgress(Rbm *pRbm, const Rbm::Status &status)
 	}
 	
 	RbmComponent *pComp = static_cast<RbmComponent*>(pRbm);
-	m_stack->upPass(pComp->id(), pComp->getTraining());
+	m_stack->upPass(pComp, pComp->getTraining());
 //	pComp->upPass(pComp->getTraining());
 	pComp->redrawReconstruction();
 	pComp->redrawWeights();
diff --git a/source/MainComponent.hpp b/source/MainComponent.hpp
index bf0092d..d24aafc 100644
--- a/source/MainComponent.hpp
+++ b/source/MainComponent.hpp
@@ -86,8 +86,8 @@ private:
 	static const size_t DBN_SIZE = 4;
 	ScopedPointer<DeepStack> m_stack;
 	RbmComponent *m_pLayer;
-	int m_weightIndex;
-	int m_trainingIndex;
+	size_t m_weightIndex;
+	size_t m_trainingIndex;
 	void save();
 	const juce::String& getBaseDir();
 	void run();
diff --git a/source/Rbm.cpp b/source/Rbm.cpp
index 6a68dbc..10fad9c 100644
--- a/source/Rbm.cpp
+++ b/source/Rbm.cpp
@@ -104,7 +104,7 @@ Json::Value Rbm::toJson() const
 	return rbm;
 }
 
-void Rbm::gibbs_vh(arma::mat &v_probs, arma::mat &h_probs)
+void Rbm::gibbs_vh(arma::mat &v_probs, arma::mat &h_probs) const
 {
 	for (int i=0; i < m_params.numGibbs; i++)
 	{
@@ -116,7 +116,7 @@ void Rbm::gibbs_vh(arma::mat &v_probs, arma::mat &h_probs)
 	}
 }
 
-void Rbm::gibbs_hv(arma::mat &h_probs, arma::mat &v_probs)
+void Rbm::gibbs_hv(arma::mat &h_probs, arma::mat &v_probs) const
 {
 	for (int i=0; i < m_params.numGibbs; i++)
 	{
diff --git a/source/Rbm.hpp b/source/Rbm.hpp
index 1e4d8c6..58edf6e 100644
--- a/source/Rbm.hpp
+++ b/source/Rbm.hpp
@@ -141,8 +141,8 @@ public:
 	arma::mat h_to_v(const arma::mat &hidden) const;
 	static arma::mat prob(arma::mat const &src);
 
-	void gibbs_hv(arma::mat &h_probs, arma::mat &v_probs);
-	void gibbs_vh(arma::mat &v_probs, arma::mat &h_probs);
+	void gibbs_hv(arma::mat &h_probs, arma::mat &v_probs) const;
+	void gibbs_vh(arma::mat &v_probs, arma::mat &h_probs) const;
 
 	static double rms_error_accu(arma::mat diffErr);
 	static arma::mat rms_error(arma::mat diffErr);
diff --git a/source/RbmComponent.cpp b/source/RbmComponent.cpp
index 3bd1907..0d7cafd 100644
--- a/source/RbmComponent.cpp
+++ b/source/RbmComponent.cpp
@@ -224,15 +224,15 @@ void RbmComponent::onDraw(DrawComponent &obj)
 {
 	if (&obj == DrawHidden)
 	{
-		m_stack.downPass(id(), obj.getData());
+		m_stack.downPass(this, obj.getData());
 	}
 	if (&obj == DrawVisibleTrain)
 	{
-		m_stack.upDownPass(id(), getTraining());
+		m_stack.upDownPass(this, getTraining());
 	}
 	if (&obj == DrawContextTrain)
 	{
-		m_stack.upDownPass(id(), getTraining());
+		m_stack.upDownPass(this, getTraining());
 	}
 }
 
@@ -266,7 +266,7 @@ void RbmComponent::buttonClicked(Button* buttonThatWasClicked)
 		if (m_numContext)
 		{
 			DrawContextTrain->getData() = DrawHidden->getData();
-			m_stack.upDownPass(id(), getTraining());
+			m_stack.upDownPass(this, getTraining());
 		}
 	}
 }
@@ -274,7 +274,7 @@ void RbmComponent::buttonClicked(Button* buttonThatWasClicked)
 void RbmComponent::redrawReconstruction()
 {
 	RbmComponent *pComp = static_cast<RbmComponent*> (root());
-	m_stack.upDownPass(pComp->id(), pComp->getTraining());
+	m_stack.upDownPass(pComp, pComp->getTraining());
 }
 
 arma::mat RbmComponent::getTraining() const
@@ -287,7 +287,7 @@ arma::mat RbmComponent::getReconst() const
 	return arma::join_rows(DrawVisibleReconst->getData(), DrawContextReconst->getData());
 }
 
-void RbmComponent::trainRedraw(const arma::mat& vc)
+void RbmComponent::trainRedraw(const arma::mat& vc) const
 {
 	DrawVisibleTrain->getData() = vc_to_v(vc);
 	DrawContextTrain->getData() = vc_to_c(vc);
@@ -295,7 +295,7 @@ void RbmComponent::trainRedraw(const arma::mat& vc)
 	DrawContextTrain->DrawData();
 }
 
-void RbmComponent::reconstRedraw(const arma::mat& vc)
+void RbmComponent::reconstRedraw(const arma::mat& vc) const
 {
 	DrawVisibleReconst->getData() = vc_to_v(vc);
 	DrawContextReconst->getData() = vc_to_c(vc);
@@ -303,7 +303,7 @@ void RbmComponent::reconstRedraw(const arma::mat& vc)
 	DrawContextReconst->DrawData();
 }
 
-void RbmComponent::onUpPass(const arma::mat& v)
+void RbmComponent::onUpPass(const arma::mat& v) const
 {
 	DrawVisibleTrain->getData() = vc_to_v(v);
 	DrawVisibleTrain->DrawData();
@@ -312,7 +312,7 @@ void RbmComponent::onUpPass(const arma::mat& v)
 	trainRedraw(v);
 }
 
-void RbmComponent::onDownPass(const arma::mat& h)
+void RbmComponent::onDownPass(const arma::mat& h) const
 {
 	DrawHidden->getData() = h;
 	DrawHidden->DrawData();
@@ -349,7 +349,7 @@ void RbmComponent::redrawWeights(size_t index)
 void RbmComponent::setTrainingData(arma::mat const& batch)
 {
 	RbmComponent *pComp = static_cast<RbmComponent*> (root());
-	m_stack.upDownPass(id(), batch);
+	m_stack.upDownPass(this, batch);
 }
 //[/MiscUserCode]
 
diff --git a/source/RbmComponent.hpp b/source/RbmComponent.hpp
index e4e14d8..c920e8f 100644
--- a/source/RbmComponent.hpp
+++ b/source/RbmComponent.hpp
@@ -73,8 +73,8 @@ public:
 	ScopedPointer<DrawComponent> DrawContextTrain;
  	arma::mat getTraining() const;
  	arma::mat getReconst() const;
-	void trainRedraw(const arma::mat& vc);
-	void reconstRedraw(const arma::mat& vc);
+	void trainRedraw(const arma::mat& vc) const;
+	void reconstRedraw(const arma::mat& vc) const;
 	
 private:
     //[UserVariables]   -- You can add your own custom variables in this section.
@@ -84,8 +84,8 @@ private:
 	ScopedPointer<ToggleButton> m_toggleEnable;
 	ScopedPointer<TextButton> m_buttonCopyH2C;
 
-	void onUpPass(const arma::mat& v) override;
-	void onDownPass(const arma::mat& h) override;
+	void onUpPass(const arma::mat& v) const override;
+	void onDownPass(const arma::mat& h) const override;
 	
 	DeepStack &m_stack;
 	size_t m_currWeightIndexToDraw;
diff --git a/source/RnnComponentLayer.cpp b/source/RnnComponentLayer.cpp
index 80653c4..a9c4f79 100644
--- a/source/RnnComponentLayer.cpp
+++ b/source/RnnComponentLayer.cpp
@@ -212,15 +212,15 @@ void RnnComponentLayer::onDraw(DrawComponent &obj)
 {
 	if (&obj == DrawHidden)
 	{
-		m_stack.downPass(id(), obj.getData());
+		m_stack.downPass(this, obj.getData());
 	}
 	if (&obj == DrawVisibleTrain)
 	{
-		m_stack.upDownPass(id(), getTraining());
+		m_stack.upDownPass(this, getTraining());
 	}
 	if (&obj == DrawContextTrain)
 	{
-		m_stack.upDownPass(id(), getTraining());
+		m_stack.upDownPass(this, getTraining());
 	}
 }
 
@@ -252,14 +252,14 @@ void RnnComponentLayer::buttonClicked(Button* buttonThatWasClicked)
 	else if (buttonThatWasClicked == m_buttonCopyH2C)
 	{
 		DrawContextTrain->getData() = DrawHidden->getData();
-		m_stack.upDownPass(id(), getTraining());
+		m_stack.upDownPass(this, getTraining());
 	}
 }
 
 void RnnComponentLayer::redrawReconstruction()
 {
 	RnnComponentLayer *pComp = static_cast<RnnComponentLayer*> (root());
-	m_stack.upDownPass(pComp->id(), pComp->getTraining());
+	m_stack.upDownPass(pComp, pComp->getTraining());
 }
 
 arma::mat RnnComponentLayer::getTraining() const
@@ -272,7 +272,7 @@ arma::mat RnnComponentLayer::getReconst() const
 	return arma::join_rows(DrawVisibleReconst->getData(), DrawContextReconst->getData());
 }
 
-void RnnComponentLayer::trainRedraw(const arma::mat& vc)
+void RnnComponentLayer::trainRedraw(const arma::mat& vc) const
 {
 	DrawVisibleTrain->getData() = vc_to_v(vc);
 	DrawContextTrain->getData() = vc_to_c(vc);
@@ -280,7 +280,7 @@ void RnnComponentLayer::trainRedraw(const arma::mat& vc)
 	DrawContextTrain->DrawData();
 }
 
-void RnnComponentLayer::reconstRedraw(const arma::mat& vc)
+void RnnComponentLayer::reconstRedraw(const arma::mat& vc) const
 {
 	DrawVisibleReconst->getData() = vc_to_v(vc);
 	DrawContextReconst->getData() = vc_to_c(vc);
@@ -288,7 +288,7 @@ void RnnComponentLayer::reconstRedraw(const arma::mat& vc)
 	DrawContextReconst->DrawData();
 }
 
-void RnnComponentLayer::onUpPass(const arma::mat& v)
+void RnnComponentLayer::onUpPass(const arma::mat& v) const
 {
 	DrawVisibleTrain->getData() = vc_to_v(v);
 	DrawVisibleTrain->DrawData();
@@ -297,7 +297,7 @@ void RnnComponentLayer::onUpPass(const arma::mat& v)
 	trainRedraw(v);
 }
 
-void RnnComponentLayer::onDownPass(const arma::mat& h)
+void RnnComponentLayer::onDownPass(const arma::mat& h) const
 {
 	DrawHidden->getData() = h;
 	DrawHidden->DrawData();
@@ -334,7 +334,7 @@ void RnnComponentLayer::redrawWeights(size_t index)
 void RnnComponentLayer::setTrainingData(arma::mat const& batch)
 {
 	RnnComponentLayer *pComp = static_cast<RnnComponentLayer*> (root());
-	m_stack.upDownPass(id(), batch);
+	m_stack.upDownPass(this, batch);
 }
 //[/MiscUserCode]
 
diff --git a/source/RnnComponentLayer.hpp b/source/RnnComponentLayer.hpp
index 4d5657c..bd793e2 100644
--- a/source/RnnComponentLayer.hpp
+++ b/source/RnnComponentLayer.hpp
@@ -73,8 +73,8 @@ public:
 	ScopedPointer<DrawComponent> DrawContextTrain;
  	arma::mat getTraining() const;
  	arma::mat getReconst() const;
-	void trainRedraw(const arma::mat& vc);
-	void reconstRedraw(const arma::mat& vc);
+	void trainRedraw(const arma::mat& vc) const;
+	void reconstRedraw(const arma::mat& vc) const;
 	
 private:
     //[UserVariables]   -- You can add your own custom variables in this section.
@@ -84,8 +84,8 @@ private:
 	ScopedPointer<ToggleButton> m_toggleEnable;
 	ScopedPointer<TextButton> m_buttonCopyH2C;
 
-	void onUpPass(const arma::mat& v) override;
-	void onDownPass(const arma::mat& h) override;
+	void onUpPass(const arma::mat& v) const override;
+	void onDownPass(const arma::mat& h) const override;
 	
 	DeepStack &m_stack;
 	size_t m_currWeightIndexToDraw;