diff --git a/source/Rbm.cpp b/source/Rbm.cpp
index 3af22aa..266c547 100644
--- a/source/Rbm.cpp
+++ b/source/Rbm.cpp
@@ -182,9 +182,7 @@ void Rbm::train(IListener* pListener)
 				lastProgress = status.progress;
 				
 				// Calculate error
-				arma::mat diffErr = miniBatch - prob(h_to_v(prob(v_to_h(v_states))));
-				arma::mat diffErr_squared = diffErr % diffErr;
-				status.err = accu(diffErr_squared)/diffErr_squared.n_elem;
+				status.err = rms_error_accu(miniBatch - prob(h_to_v(prob(v_to_h(v_states)))));
 				if (pListener)
 				{
 					if(!pListener->onProgress(this, status))
@@ -200,9 +198,7 @@ void Rbm::train(IListener* pListener)
 	} // number of mini batches
 
 	// Update final status
-	arma::mat diffErr = batch - prob(h_to_v(prob(v_to_h(batch))));
-	arma::mat diffErr_squared = diffErr % diffErr;
-	status.err_total = accu(diffErr_squared)/diffErr_squared.n_elem;
+	status.err_total = rms_error_accu(batch - prob(h_to_v(prob(v_to_h(batch)))));
 
 	if (pListener)
 	{
diff --git a/source/Rbm.hpp b/source/Rbm.hpp
index fb8390b..3a63200 100644
--- a/source/Rbm.hpp
+++ b/source/Rbm.hpp
@@ -170,6 +170,18 @@ public:
 	arma::mat v_to_h(const arma::mat &visible) const;
 	arma::mat h_to_v(const arma::mat &hidden) const;
 
+	static double rms_error_accu(arma::mat diffErr)
+	{
+		arma::mat diffErr_squared = diffErr % diffErr;
+		return arma::accu(diffErr_squared)/diffErr_squared.n_elem;
+	}
+
+	static arma::mat rms_error(arma::mat diffErr)
+	{
+		arma::mat diffErr_squared = diffErr % diffErr;
+		return arma::sum(diffErr_squared, 1) * 1.0/diffErr_squared.n_cols;
+	}
+	
 private:
 	Params m_params;
 	arma::mat sample(arma::mat const &src);