CG test written and passes i.e. converges with small true residual

in RedBlack MpcDagMpc, Unprec MdagM and Schur red black solver for
each of.

DomainWallFermion
MobiusFermion
MobiusZolotarevFermion
ScaledShamirFermion
ScaledShamirZolotarevFermion

tests/Test_cshift.cc

@@ -0,0 +1,86 @@
+#include <Grid.h>
+#include <parallelIO/GridNerscIO.h>
+
+using namespace Grid;
+using namespace Grid::QCD;
+
+int main (int argc, char ** argv)
+{
+  Grid_init(&argc,&argv);
+
+  std::vector<int> latt_size   = GridDefaultLatt();
+  std::vector<int> simd_layout = GridDefaultSimd(4,vComplexF::Nsimd());
+  std::vector<int> mpi_layout  = GridDefaultMpi();
+
+  GridCartesian        Fine(latt_size,simd_layout,mpi_layout);
+
+  GridParallelRNG      FineRNG(&Fine);  FineRNG.SeedRandomDevice();
+
+  LatticeComplex U(&Fine);
+  LatticeComplex ShiftU(&Fine);
+
+  LatticeComplex lex(&Fine);
+  lex=zero;
+  Integer stride =1;
+  {
+    double nrm;
+    LatticeComplex coor(&Fine);
+
+    for(int d=0;d<4;d++){
+      LatticeCoordinate(coor,d);
+      lex = lex + coor*stride;
+      stride=stride*latt_size[d];
+    }
+    U=lex;
+  }
+
+
+
+  TComplex cm;
+  
+  for(int dir=0;dir<4;dir++){
+    for(int shift=0;shift<latt_size[dir];shift++){
+      if ( Fine.IsBoss() ) 
+	std::cout<<"Shifting by "<<shift<<" in direction"<<dir<<std::endl;
+
+	ShiftU  = Cshift(U,dir,shift);    // Shift everything
+
+	std::vector<int> coor(4);
+
+	for(coor[3]=0;coor[3]<latt_size[3];coor[3]++){
+	for(coor[2]=0;coor[2]<latt_size[2];coor[2]++){
+	for(coor[1]=0;coor[1]<latt_size[1];coor[1]++){
+	for(coor[0]=0;coor[0]<latt_size[0];coor[0]++){
+	  
+	  peekSite(cm,ShiftU,coor);
+
+	  double nrm=norm2(U);
+
+	  std::vector<int> scoor(coor);
+	  scoor[dir] = (scoor[dir]+shift)%latt_size[dir];
+	  
+	  Integer slex = scoor[0]
+	    + latt_size[0]*scoor[1]
+	    + latt_size[0]*latt_size[1]*scoor[2]
+	    + latt_size[0]*latt_size[1]*latt_size[2]*scoor[3];
+
+	  Complex scm(slex);
+	  
+	  nrm = abs(scm-cm()()());
+	  std::vector<int> peer(4);
+	  int index=real(cm);
+	  Fine.CoorFromIndex(peer,index,latt_size);
+
+	  if (nrm > 0){
+	    std::cerr<<"FAIL shift "<< shift<<" in dir "<< dir<<" ["<<coor[0]<<","<<coor[1]<<","<<coor[2]<<","<<coor[3]<<"] = "<< cm()()()<<" expect "<<scm<<"  "<<nrm<<std::endl;
+	    std::cerr<<"Got    "<<index<<" " << peer[0]<<","<<peer[1]<<","<<peer[2]<<","<<peer[3]<<std::endl;
+	    index=real(scm);
+	    Fine.CoorFromIndex(peer,index,latt_size);
+	    std::cerr<<"Expect "<<index<<" " << peer[0]<<","<<peer[1]<<","<<peer[2]<<","<<peer[3]<<std::endl;
+	  }
+	}}}}
+    }
+  }
+
+  Grid_finalize();
+}