From 96bf814d8c85a5fa79f55a9c381e9cc17e0fb07e Mon Sep 17 00:00:00 2001
From: Christoph Lehner <christoph@lhnr.de>
Date: Thu, 10 Apr 2025 22:14:55 +0200
Subject: [PATCH] Add checkerboarding to 5D compact clover

---
 Grid/qcd/action/fermion/WilsonFermion5D.h     | 12 ++---
 .../WilsonFermion5DImplementation.h           | 49 +++++++++++++++++++
 2 files changed, 55 insertions(+), 6 deletions(-)

diff --git a/Grid/qcd/action/fermion/WilsonFermion5D.h b/Grid/qcd/action/fermion/WilsonFermion5D.h
index 40c1871f..9dadc866 100644
--- a/Grid/qcd/action/fermion/WilsonFermion5D.h
+++ b/Grid/qcd/action/fermion/WilsonFermion5D.h
@@ -91,13 +91,13 @@ public:
   virtual void   Mdag (const FermionField &in, FermionField &out){assert(0);};
 
   // half checkerboard operations; leave unimplemented as abstract for now
-  virtual void   Meooe       (const FermionField &in, FermionField &out){assert(0);};
-  virtual void   Mooee       (const FermionField &in, FermionField &out){assert(0);};
-  virtual void   MooeeInv    (const FermionField &in, FermionField &out){assert(0);};
+  virtual void   Meooe       (const FermionField &in, FermionField &out);
+  virtual void   Mooee       (const FermionField &in, FermionField &out);
+  virtual void   MooeeInv    (const FermionField &in, FermionField &out);
 
-  virtual void   MeooeDag    (const FermionField &in, FermionField &out){assert(0);};
-  virtual void   MooeeDag    (const FermionField &in, FermionField &out){assert(0);};
-  virtual void   MooeeInvDag (const FermionField &in, FermionField &out){assert(0);};
+  virtual void   MeooeDag    (const FermionField &in, FermionField &out);
+  virtual void   MooeeDag    (const FermionField &in, FermionField &out);
+  virtual void   MooeeInvDag (const FermionField &in, FermionField &out);
   virtual void   Mdir   (const FermionField &in, FermionField &out,int dir,int disp){assert(0);};   // case by case Wilson, Clover, Cayley, ContFrac, PartFrac
   virtual void   MdirAll(const FermionField &in, std::vector<FermionField> &out){assert(0);};   // case by case Wilson, Clover, Cayley, ContFrac, PartFrac
 
diff --git a/Grid/qcd/action/fermion/implementation/WilsonFermion5DImplementation.h b/Grid/qcd/action/fermion/implementation/WilsonFermion5DImplementation.h
index 3d4e5cc5..9598552f 100644
--- a/Grid/qcd/action/fermion/implementation/WilsonFermion5DImplementation.h
+++ b/Grid/qcd/action/fermion/implementation/WilsonFermion5DImplementation.h
@@ -14,6 +14,7 @@ Author: paboyle <paboyle@ph.ed.ac.uk>
 Author: Guido Cossu <guido.cossu@ed.ac.uk>
 Author: Andrew Lawson <andrew.lawson1991@gmail.com>
 Author: Vera Guelpers <V.M.Guelpers@soton.ac.uk>
+Author: Christoph Lehner <christoph@lhnr.de>
 
     This program is free software; you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
@@ -484,6 +485,54 @@ void WilsonFermion5D<Impl>::DW(const FermionField &in, FermionField &out,int dag
   Dhop(in,out,dag); // -0.5 is included
   axpy(out,4.0-M5,in,out);
 }
+template <class Impl>
+void WilsonFermion5D<Impl>::Meooe(const FermionField &in, FermionField &out)
+{
+  if (in.Checkerboard() == Odd) {
+    DhopEO(in, out, DaggerNo);
+  } else {
+    DhopOE(in, out, DaggerNo);
+  }
+}
+
+template <class Impl>
+void WilsonFermion5D<Impl>::MeooeDag(const FermionField &in, FermionField &out)
+{
+  if (in.Checkerboard() == Odd) {
+    DhopEO(in, out, DaggerYes);
+  } else {
+    DhopOE(in, out, DaggerYes);
+  }
+}
+
+template <class Impl>
+void WilsonFermion5D<Impl>::Mooee(const FermionField &in, FermionField &out)
+{
+  out.Checkerboard() = in.Checkerboard();
+  typename FermionField::scalar_type scal(4.0 + M5);
+  out = scal * in;
+}
+
+template <class Impl>
+void WilsonFermion5D<Impl>::MooeeDag(const FermionField &in, FermionField &out)
+{
+  out.Checkerboard() = in.Checkerboard();
+  Mooee(in, out);
+}
+
+template<class Impl>
+void WilsonFermion5D<Impl>::MooeeInv(const FermionField &in, FermionField &out)
+{
+  out.Checkerboard() = in.Checkerboard();
+  out = (1.0/(4.0 + M5))*in;
+}
+
+template<class Impl>
+void WilsonFermion5D<Impl>::MooeeInvDag(const FermionField &in, FermionField &out)
+{
+  out.Checkerboard() = in.Checkerboard();
+  MooeeInv(in,out);
+}
 
 template<class Impl>
 void WilsonFermion5D<Impl>::MomentumSpacePropagatorHt_5d(FermionField &out,const FermionField &in, RealD mass,std::vector<double> twist)