diff --git a/FDTD/engine_mpi.cpp b/FDTD/engine_mpi.cpp
index 28bfe76..bf5139f 100644
--- a/FDTD/engine_mpi.cpp
+++ b/FDTD/engine_mpi.cpp
@@ -46,7 +46,7 @@ void Engine_MPI::Init()
 		m_BufferSize[i]=0;
 	}
 
-	if (m_Op_MPI->m_NumProc>1)
+	if (m_Op_MPI->GetMPIEnabled())
 	{
 		// init buffers, nx*ny*2 for the tangential electric or magnetic fields at the interface
 		m_BufferSize[2] = m_Op_MPI->numLines[0]*m_Op_MPI->numLines[1]*2;
@@ -178,6 +178,11 @@ void Engine_MPI::SendReceiveCurrents()
 
 bool Engine_MPI::IterateTS(unsigned int iterTS)
 {
+	if (!m_Op_MPI->GetMPIEnabled())
+	{
+		return Engine_SSE_Compressed::IterateTS(iterTS);
+	}
+
 	for (unsigned int iter=0; iter<iterTS; ++iter)
 	{
 		//voltage updates with extensions
diff --git a/FDTD/operator_mpi.cpp b/FDTD/operator_mpi.cpp
index 6d1f756..cc0f5bf 100644
--- a/FDTD/operator_mpi.cpp
+++ b/FDTD/operator_mpi.cpp
@@ -33,6 +33,10 @@ Operator_MPI* Operator_MPI::New()
 
 Operator_MPI::Operator_MPI() : Operator_SSE_Compressed()
 {
+	m_NumProc = MPI::COMM_WORLD.Get_size();
+
+	//enabled only if more than one process is active
+	m_MPI_Enabled = m_NumProc>0;
 }
 
 Operator_MPI::~Operator_MPI()
@@ -44,7 +48,7 @@ bool Operator_MPI::SetGeometryCSX(ContinuousStructure* geo)
 {
 	//manipulate geometry for this part...
 
-	if (m_NumProc>1)
+	if (m_MPI_Enabled)
 	{
 		CSRectGrid* grid = geo->GetGrid();
 		int nz = grid->GetQtyLines(2);
@@ -71,8 +75,28 @@ bool Operator_MPI::SetGeometryCSX(ContinuousStructure* geo)
 	return Operator_SSE_Compressed::SetGeometryCSX(geo);
 }
 
+double Operator_MPI::CalcTimestep()
+{
+	double ret = Operator::CalcTimestep();
+
+	if (!m_MPI_Enabled)
+		return ret;
+
+	double local_dT = dT;
+	//find the smallest time-step requestes by all processings
+	MPI_Reduce(&local_dT, &dT, 1, MPI_DOUBLE, MPI_MIN, 0, MPI_COMM_WORLD);
+	//send the smallest time-step to all
+	MPI_Bcast(&dT, 1, MPI_DOUBLE, 0, MPI_COMM_WORLD);
+
+	return ret;
+}
+
+
 void Operator_MPI::SetBoundaryCondition(int* BCs)
 {
+	if (!m_MPI_Enabled)
+		return Operator_SSE_Compressed::SetBoundaryCondition(BCs);
+
 	//set boundary conditions on MPI interfaces to PEC, ApplyElectricBC will handle proper interface handling...
 	for (int n=0;n<3;++n)
 	{
@@ -86,6 +110,9 @@ void Operator_MPI::SetBoundaryCondition(int* BCs)
 
 void Operator_MPI::ApplyElectricBC(bool* dirs)
 {
+	if (!m_MPI_Enabled)
+		return Operator_SSE_Compressed::ApplyElectricBC(dirs);
+
 	for (int n=0;n<3;++n)
 	{
 		//do not delete operator at upper inteface
@@ -97,7 +124,7 @@ void Operator_MPI::ApplyElectricBC(bool* dirs)
 
 Engine* Operator_MPI::CreateEngine() const
 {
-	if (m_NumProc>1)
+	if (m_MPI_Enabled)
 		return Engine_MPI::New(this);
 	else
 		return Engine_SSE_Compressed::New(this);
@@ -122,7 +149,8 @@ void Operator_MPI::Init()
 	m_Processor_Name = new char[MPI_MAX_PROCESSOR_NAME];
 	MPI::Get_processor_name(m_Processor_Name,namelen);
 
-	cerr << "Operator_MPI::Init(): Running on " << m_Processor_Name << endl;
+	if (m_MPI_Enabled)
+		cerr << "Operator_MPI::Init(): Running on " << m_Processor_Name << endl;
 }
 
 void Operator_MPI::Delete()
diff --git a/FDTD/operator_mpi.h b/FDTD/operator_mpi.h
index 4cae2fb..902507b 100644
--- a/FDTD/operator_mpi.h
+++ b/FDTD/operator_mpi.h
@@ -28,6 +28,8 @@ public:
 	static Operator_MPI* New();
 	virtual ~Operator_MPI();
 
+	bool GetMPIEnabled() const {return m_MPI_Enabled;}
+
 	virtual bool SetGeometryCSX(ContinuousStructure* geo);
 
 	virtual void SetBoundaryCondition(int* BCs);
@@ -37,10 +39,13 @@ public:
 
 protected:
 	Operator_MPI();
+	bool m_MPI_Enabled;
 	virtual void Init();
 	void Delete();
 	virtual void Reset();
 
+	virtual double CalcTimestep();
+
 	int m_MyID;
 	int m_NumProc;
 	int m_MyTag;