From addeb621a7015cb690a08d4650e8f2b10568fbf7 Mon Sep 17 00:00:00 2001
From: Andrew Zhen Ning Yong <andrew.yong@ed.ac.uk>
Date: Tue, 6 Apr 2021 13:45:37 +0100
Subject: [PATCH] Implemented tadpole operator for Shamir action.

---
 .../implementation/CayleyFermion5DImplementation.h | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/Grid/qcd/action/fermion/implementation/CayleyFermion5DImplementation.h b/Grid/qcd/action/fermion/implementation/CayleyFermion5DImplementation.h
index f11e9c44..c3e0f821 100644
--- a/Grid/qcd/action/fermion/implementation/CayleyFermion5DImplementation.h
+++ b/Grid/qcd/action/fermion/implementation/CayleyFermion5DImplementation.h
@@ -880,11 +880,23 @@ void CayleyFermion5D<Impl>::SeqConservedCurrent(PropagatorField &q_in,
   }
 
   std::vector<RealD> G_s(Ls,1.0);
+  Integer sign = 1; // sign flip for vector/tadpole
   if ( curr_type == Current::Axial ) {
     for(int s=0;s<Ls/2;s++){
       G_s[s] = -1.0;
     }
   }
+  else if ( curr_type == Current::Tadpole ) {
+    auto b=this->_b;
+    auto c=this->_c;
+    if ( b == 1 && c == 0 ) {
+      sign = -1;    
+    }
+    else {
+      std::cerr << "Error: Tadpole implementation currently unavailable for non-Shamir actions." << std::endl;
+      assert(b==1 && c==0);
+    }
+  }
 
   for(int s=0;s<Ls;s++){
 
@@ -907,7 +919,7 @@ void CayleyFermion5D<Impl>::SeqConservedCurrent(PropagatorField &q_in,
 
     tmp    = Cshift(tmp,mu,1);
     Impl::multLinkField(Utmp,this->Umu,tmp,mu);
-    tmp    = G_s[s]*( Utmp*ph - gmu*Utmp*ph ); // Forward hop
+    tmp    = sign*G_s[s]*( Utmp*ph - gmu*Utmp*ph ); // Forward hop
     tmp    = where((lcoor>=tmin),tmp,zz); // Mask the time 
     L_Q    = where((lcoor<=tmax),tmp,zz); // Position of current complicated