Domain wall fermions now invert ; have the basis set up for

Tanh/Zolo * (Cayley/PartFrac/ContFrac) * (Mobius/Shamir/Wilson)
Approx        Representation               Kernel.

All are done with space-time taking part in checkerboarding, Ls uncheckerboarded

Have only so far tested the Domain Wall limit of mobius, and at that only checked
that it
i)  Inverts
ii) 5dim DW == Ls copies of 4dim D2
iii) MeeInv Mee == 1
iv) Meo+Mee+Moe+Moo == M unprec.
v) MpcDagMpc is hermitan
vi) Mdag is the adjoint of M between stochastic vectors.

That said, the RB schur solve, RB MpcDagMpc solve, Unprec solve
all converge and the true residual becomes small; so pretty good tests.

lib/qcd/action/fermion/CayleyFermion5D.h

@@ -0,0 +1,61 @@
+#ifndef  GRID_QCD_CAYLEY_FERMION_H
+#define  GRID_QCD_CAYLEY_FERMION_H
+
+namespace Grid {
+
+  namespace QCD {
+
+    class CayleyFermion5D : public WilsonFermion5D
+    {
+    public:
+
+      // override multiply
+      virtual RealD  M    (const LatticeFermion &in, LatticeFermion &out);
+      virtual RealD  Mdag (const LatticeFermion &in, LatticeFermion &out);
+
+      // half checkerboard operations
+      virtual void   Meooe       (const LatticeFermion &in, LatticeFermion &out);
+      virtual void   MeooeDag    (const LatticeFermion &in, LatticeFermion &out);
+      virtual void   Mooee       (const LatticeFermion &in, LatticeFermion &out);
+      virtual void   MooeeDag    (const LatticeFermion &in, LatticeFermion &out);
+      virtual void   MooeeInv    (const LatticeFermion &in, LatticeFermion &out);
+      virtual void   MooeeInvDag (const LatticeFermion &in, LatticeFermion &out);
+
+      //    protected:
+
+      Approx::zolotarev_data *zdata;
+
+      RealD mass;
+      // Cayley form Moebius (tanh and zolotarev)
+      std::vector<RealD> omega; 
+      std::vector<RealD> bs;    // S dependent coeffs
+      std::vector<RealD> cs;    
+      std::vector<RealD> as;    
+      // For preconditioning Cayley form
+      std::vector<RealD> bee;    
+      std::vector<RealD> cee;    
+      std::vector<RealD> aee;    
+      std::vector<RealD> beo;    
+      std::vector<RealD> ceo;    
+      std::vector<RealD> aeo;    
+      // LDU factorisation of the eeoo matrix
+      std::vector<RealD> lee;    
+      std::vector<RealD> leem;    
+      std::vector<RealD> uee;    
+      std::vector<RealD> ueem;    
+      std::vector<RealD> dee;    
+
+      // Constructors
+      CayleyFermion5D(LatticeGaugeField &_Umu,
+		      GridCartesian         &FiveDimGrid,
+		      GridRedBlackCartesian &FiveDimRedBlackGrid,
+		      GridCartesian         &FourDimGrid,
+		      GridRedBlackCartesian &FourDimRedBlackGrid,
+		      RealD _mass,RealD _M5);
+
+    };
+
+  }
+}
+
+#endif