diff --git a/lib/qcd/action/pseudofermion/TwoFlavourRatio.h b/lib/qcd/action/pseudofermion/TwoFlavourRatio.h
new file mode 100644
index 00000000..1098c85a
--- /dev/null
+++ b/lib/qcd/action/pseudofermion/TwoFlavourRatio.h
@@ -0,0 +1,132 @@
+#ifndef QCD_PSEUDOFERMION_TWO_FLAVOUR_H
+#define QCD_PSEUDOFERMION_TWO_FLAVOUR_H
+
+namespace Grid{
+  namespace QCD{
+
+    ///////////////////////////////////////
+    // Two flavour ratio
+    ///////////////////////////////////////
+    template<class Impl>
+    class TwoFlavourRatioPseudoFermionAction : public Action<typename Impl::GaugeField> {
+    public:
+      INHERIT_IMPL_TYPES(Impl);
+
+    private:
+      FermionOperator<Impl> & NumOp;// the basic operator
+      FermionOperator<Impl> & DenOp;// the basic operator
+
+      OperatorFunction<FermionField> &DerivativeSolver;
+      OperatorFunction<FermionField> &ActionSolver;
+
+      FermionField Phi; // the pseudo fermion field for this trajectory
+
+    public:
+      TwoFlavourRatioPseudoFermionAction(FermionOperator<Impl>  &_NumOp, 
+					 FermionOperator<Impl>  &_DenOp, 
+					 OperatorFunction<FermionField> & DS,
+					 OperatorFunction<FermionField> & AS
+					 ) : NumOp(_NumOp), DenOp(_DenOp), DerivativeSolver(DS), ActionSolver(AS), Phi(Op.FermionGrid()) {};
+      
+      virtual void init(const GaugeField &U, GridParallelRNG& pRNG) {
+
+	// P(phi) = e^{- phi^dag V (MdagM)^-1 Vdag phi}
+	//
+	// phi = Vdag^{-1} Mdag eta 
+	//
+	// P(eta) = e^{- eta^dag eta}
+	//
+	// e^{x^2/2 sig^2} => sig^2 = 0.5.
+	// 
+	// So eta should be of width sig = 1/sqrt(2).
+	// and must multiply by 0.707....
+	//
+	RealD scale = std::sqrt(0.5);
+
+	FermionField eta(NumOp.FermionGrid());
+
+	gaussian(pRNG,eta);
+
+	NumOp.ImportGauge(U);
+	DenOp.ImportGauge(U);
+
+	MdagMLinearOperator<FermionOperator<Impl> ,FermionField> MdagMOp(NumOp);
+
+	DenOp.Mdag(eta,Phi);            // Mdag eta
+	ActionSolver(MdagMOp,Phi,tmp);  // (VdagV)^-1 Mdag eta = V^-1 Vdag^-1 Mdag eta
+	NumOp.M(tmp,Phi);               // Vdag^-1 Mdag eta
+
+	Phi=Phi*scale;
+	
+      };
+
+      //////////////////////////////////////////////////////
+      // S = phi^dag V (Mdag M)^-1 Vdag phi
+      //////////////////////////////////////////////////////
+      virtual RealD S(const GaugeField &U) {
+
+	NumOp.ImportGauge(U);
+	DenOp.ImportGauge(U);
+
+	FermionField X(NumOp.FermionGrid());
+	FermionField Y(NumOp.FermionGrid());
+	
+	MdagMLinearOperator<FermionOperator<Impl> ,FermionField> MdagMOp(DenOp);
+
+	X=zero;
+	NumOp.Mdag(Phi,Y);              // Vdag phi
+	ActionSolver(MdagMOp,Y,X);      // MdagMinv Vdag phi
+	MdagMOp.Op(X,Y);                // Y=Mdaginv Vdag phi
+
+	RealD action = norm2(Y);
+
+	return action;
+      };
+
+      //////////////////////////////////////////////////////
+      // dS/du = phi^dag dV (Mdag M)^-1 V^dag  phi
+      //       - phi^dag V (Mdag M)^-1 [ Mdag dM + dMdag M ]  (Mdag M)^-1 V^dag  phi
+      //       + phi^dag V (Mdag M)^-1 dV^dag  phi
+      //////////////////////////////////////////////////////
+      virtual void deriv(const GaugeField &U,GaugeField & dSdU) {
+
+	NumOp.ImportGauge(U);
+	DenOp.ImportGauge(U);
+
+	MdagMLinearOperator<FermionOperator<Impl> ,FermionField> MdagMOp(DenOp);
+
+	FermionField  X(NumOp.FermionGrid());
+	FermionField  Y(NumOp.FermionGrid());
+	FermionField f1(NumOp.FermionGrid());
+
+	GaugeField   force(FermOp.GaugeGrid());	
+
+	X=zero;
+
+	//f1=Vdag phi
+	NumOp.Mdag(phi,f1);   
+
+	//X = (Mdag M)^-1 V^dag phi
+	DerivativeSolver(MdagMOp,f1,X);
+
+	//Y = (Mdag)^-1 V^dag  phi
+	DenOp.M(X,Y);
+
+	// phi^dag V (Mdag M)^-1 dV^dag  phi
+	NumOp.MDeriv(force , X, Phi, DaggerYes );  dSdU=force;
+  
+	// phi^dag dV (Mdag M)^-1 V^dag  phi
+	NumOp.MDeriv(force , Phi, X ,DaggerNo  );  dSdU=dSdU+force;
+
+	//    -    phi^dag V (Mdag M)^-1 Mdag dM   (Mdag M)^-1 V^dag  phi
+	//    -    phi^dag V (Mdag M)^-1 dMdag M   (Mdag M)^-1 V^dag  phi
+	DenOp.MDeriv(force,Y,X,DaggerNo);   dSdU=dSdU-force;
+	DenOp.MDeriv(force,X,Y,DaggerYes);  dSdU=dSdU-force;
+	
+	dSdU = Ta(dSdU);
+
+      };
+    };
+  }
+}
+#endif