diff --git a/tests/debug/Test_split_laplacian.cc b/tests/debug/Test_split_laplacian.cc
new file mode 100644
index 00000000..174dc1b1
--- /dev/null
+++ b/tests/debug/Test_split_laplacian.cc
@@ -0,0 +1,104 @@
+    /*************************************************************************************
+
+    Grid physics library, www.github.com/paboyle/Grid 
+
+    Source file: ./tests/Test_dwf_mrhs_cg.cc
+
+    Copyright (C) 2015
+
+Author: Peter Boyle <paboyle@ph.ed.ac.uk>
+
+    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
+    the Free Software Foundation; either version 2 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License along
+    with this program; if not, write to the Free Software Foundation, Inc.,
+    51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+
+    See the full license in the file "LICENSE" in the top level distribution directory
+    *************************************************************************************/
+    /*  END LEGAL */
+#include <Grid/Grid.h>
+
+using namespace std;
+using namespace Grid;
+using namespace Grid::QCD;
+
+
+int main (int argc, char ** argv)
+{
+  typedef LatticeComplex ComplexField; 
+
+  Grid_init(&argc,&argv);
+
+  std::vector<int> latt_size   = GridDefaultLatt();
+  int nd   = latt_size.size();
+  int ndm1 = nd-1;
+
+  std::vector<int> simd_layout = GridDefaultSimd(nd,vComplex::Nsimd());
+  std::vector<int> mpi_layout  = GridDefaultMpi();
+  std::vector<int> mpi_split (mpi_layout.size(),1);
+
+  std::cout << " Full " << GridCmdVectorIntToString(latt_size)  << " subgrid"         <<std::endl;
+  std::cout << " Full " << GridCmdVectorIntToString(mpi_layout) << " sub communicator"<<std::endl;
+  std::cout << " Full " << GridCmdVectorIntToString(simd_layout)<< " simd layout "    <<std::endl;
+
+  GridCartesian         * GridN = new GridCartesian(latt_size,
+						    simd_layout,
+						    mpi_layout);
+
+  std::vector<int> latt_m  = latt_size;   latt_m[nd-1] = 1;
+  std::vector<int> mpi_m   = mpi_layout;  mpi_m [nd-1] = 1;
+  std::vector<int> simd_m  = GridDefaultSimd(ndm1,vComplex::Nsimd()); simd_m.push_back(1);
+
+
+  std::cout << " Requesting " << GridCmdVectorIntToString(latt_m)<< " subgrid"         <<std::endl;
+  std::cout << " Requesting " << GridCmdVectorIntToString(mpi_m) << " sub communicator"<<std::endl;
+  std::cout << " Requesting " << GridCmdVectorIntToString(simd_m)<< " simd layout "    <<std::endl;
+  GridCartesian         * Grid_m = new GridCartesian(latt_m,
+						     simd_m,
+						     mpi_m,
+						     *GridN); 
+
+  Complex C(1.0);
+  Complex tmp;
+
+  ComplexField Full(GridN); Full = C;
+  ComplexField Full_cpy(GridN);
+  ComplexField Split(Grid_m);Split= C;
+
+  std::cout << GridLogMessage<< " Full  volume "<< norm2(Full) <<std::endl;
+  std::cout << GridLogMessage<< " Split volume "<< norm2(Split) <<std::endl;
+
+  tmp=C;
+  GridN->GlobalSum(tmp);
+  std::cout << GridLogMessage<< " Full  nodes "<< tmp <<std::endl;
+
+  tmp=C;
+  Grid_m->GlobalSum(tmp);
+  std::cout << GridLogMessage<< " Split nodes "<< tmp <<std::endl;
+  GridN->Barrier();
+
+  auto local_latt = GridN->LocalDimensions();
+
+  Full_cpy = zero;
+  std::vector<int> seeds({1,2,3,4});
+  GridParallelRNG          RNG(GridN);  RNG.SeedFixedIntegers(seeds);
+
+  random(RNG,Full);
+  for(int t=0;t<local_latt[nd-1];t++){
+    ExtractSliceLocal(Split,Full,0,t,Tp);
+    InsertSliceLocal (Split,Full_cpy,0,t,Tp);
+  }
+  Full_cpy = Full_cpy - Full;
+  std::cout << " NormFull " << norm2(Full)<<std::endl;
+  std::cout << " NormDiff " << norm2(Full_cpy)<<std::endl;
+  Grid_finalize();
+}