Improving efficiency of the force term

lib/qcd/action/scalar/ScalarInteractionAction.h

@@ -30,17 +30,34 @@ directory
 #ifndef SCALAR_INT_ACTION_H
 #define SCALAR_INT_ACTION_H
 
+
+// Note: this action can completely absorb the ScalarAction for real float fields
+// use the scalarObjs to generalise the structure
+
 namespace Grid {
   // FIXME drop the QCD namespace everywhere here
 
 template <class Impl>
 class ScalarInteractionAction : public QCD::Action<typename Impl::Field> {
+public:
+    INHERIT_FIELD_TYPES(Impl);
+private:
     RealD mass_square;
     RealD lambda;
 
+
+    typedef typename Field::vector_object vobj;
+    typedef CartesianStencil<vobj,vobj> Stencil;
+
+    SimpleCompressor<vobj> compressor;
+    int npoint = 8;
+    std::vector<int> directions    = {0,1,2,3,0,1,2,3};  // forcing 4 dimensions
+    std::vector<int> displacements = {1,1,1,1, -1,-1,-1,-1};
+
+
  public:
-    INHERIT_FIELD_TYPES(Impl);
+
-    ScalarInteractionAction(RealD ms, RealD l) : mass_square(ms), lambda(l) {}
+    ScalarInteractionAction(RealD ms, RealD l) : mass_square(ms), lambda(l){}
 
     virtual std::string LogParameters() {
       std::stringstream sstream;
@@ -51,27 +68,75 @@ class ScalarInteractionAction : public QCD::Action<typename Impl::Field> {
 
     virtual std::string action_name() {return "ScalarAction";}
 
-    virtual void refresh(const Field &U,
+    virtual void refresh(const Field &U, GridParallelRNG &pRNG) {}
-                         GridParallelRNG &pRNG) {}  // noop as no pseudoferms
 
     virtual RealD S(const Field &p) {
-        Field action(p._grid);
+        static Stencil phiStencil(p._grid, npoint, 0, directions, displacements);
-        Field pshift(p._grid);
+        phiStencil.HaloExchange(p, compressor);
-        Field phisquared(p._grid);
+
+        Field action(p._grid), pshift(p._grid), phisquared(p._grid);
         phisquared = p*p;
         action = (2.0*QCD::Nd + mass_square)*phisquared + lambda*phisquared*phisquared;
         for (int mu = 0; mu < QCD::Nd; mu++) {
-            pshift = Cshift(p, mu, +1);  // not efficient implement with stencils
+            //  pshift = Cshift(p, mu, +1);  // not efficient, implement with stencils
-            action -= pshift*p + p*pshift;
+            PARALLEL_FOR_LOOP
+            for (int i = 0; i < p._grid->oSites(); i++) {
+                int permute_type;
+                StencilEntry *SE;
+                vobj temp2;
+                vobj *temp;
+                vobj *t_p;
+
+                SE = phiStencil.GetEntry(permute_type, mu, i);
+                t_p  = &p._odata[i];
+                if ( SE->_is_local ) {
+                    temp = &p._odata[SE->_offset];
+                    if ( SE->_permute ) {
+                        permute(temp2, *temp, permute_type);
+                        action._odata[i] -= temp2*(*t_p) + (*t_p)*temp2;
+                    } else {
+                  action._odata[i] -= *temp*(*t_p) + (*t_p)*(*temp);
+                    }
+                } else {
+                  action._odata[i] -= phiStencil.CommBuf()[SE->_offset]*(*t_p) + (*t_p)*phiStencil.CommBuf()[SE->_offset];
+                }
+            }
+            //  action -= pshift*p + p*pshift;
         }
+        // NB the trace in the algebra is normalised to 1/2
+        // minus sign coming from the antihermitian fields
         return -(TensorRemove(sum(trace(action)))).real();
     };
 
-    virtual void deriv(const Field &p,
+    virtual void deriv(const Field &p, Field &force) {
-                       Field &force) {
         force = (2.0*QCD::Nd + mass_square)*p + 2.0*lambda*p*p*p;
-        // following is inefficient
+        // move this outside
-        for (int mu = 0; mu < QCD::Nd; mu++) force -= Cshift(p, mu, -1) + Cshift(p, mu, 1);
+        static Stencil phiStencil(p._grid, npoint, 0, directions, displacements);
+        phiStencil.HaloExchange(p, compressor);
+
+        //for (int mu = 0; mu < QCD::Nd; mu++) force -= Cshift(p, mu, -1) + Cshift(p, mu, 1);
+        for (int point = 0; point < npoint; point++) {
+            PARALLEL_FOR_LOOP
+            for (int i = 0; i < p._grid->oSites(); i++) {
+                vobj *temp;
+                vobj temp2;
+                int permute_type;
+                StencilEntry *SE;
+                SE = phiStencil.GetEntry(permute_type, point, i);
+
+                if ( SE->_is_local ) {
+                    temp = &p._odata[SE->_offset];
+                    if ( SE->_permute ) {
+                        permute(temp2, *temp, permute_type);
+                        force._odata[i] -= temp2;
+                    } else {
+                        force._odata[i] -= *temp;
+                    }
+                } else {
+                    force._odata[i] -= phiStencil.CommBuf()[SE->_offset];
+                }
+            }
+        }
     }
 };
 

tests/Test_stencil.cc

@@ -33,9 +33,8 @@ using namespace std;
 using namespace Grid;
 using namespace Grid::QCD;
 
-int main (int argc, char ** argv)
+int main(int argc, char ** argv) {
-{
+  Grid_init(&argc, &argv);
-  Grid_init(&argc,&argv);
 
   //  typedef LatticeColourMatrix Field;
   typedef LatticeComplex Field;

tests/hmc/Test_hmc_ScalarActionNxN.cc

@@ -26,7 +26,7 @@ See the full license in the file "LICENSE" in the top level distribution directo
 *************************************************************************************/
 /*  END LEGAL */
 #include <Grid/Grid.h>
-namespace Grid{
+namespace Grid {
 class ScalarActionParameters : Serializable {
  public:
   GRID_SERIALIZABLE_CLASS_MEMBERS(ScalarActionParameters,
@@ -44,7 +44,7 @@ int main(int argc, char **argv) {
   // here make a routine to print all the relevant information on the run
   std::cout << GridLogMessage << "Grid is setup to use " << threads << " threads" << std::endl;
 
-   // Typedefs to simplify notation
+  // Typedefs to simplify notation
   typedef ScalarAdjGenericHMCRunner HMCWrapper;  // Uses the default minimum norm, real scalar fields
 
   //::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
@@ -52,7 +52,7 @@ int main(int argc, char **argv) {
 
   // Grid from the command line
   GridModule ScalarGrid;
-  ScalarGrid.set_full( SpaceTimeGrid::makeFourDimGrid(
+  ScalarGrid.set_full(SpaceTimeGrid::makeFourDimGrid(
         GridDefaultLatt(), GridDefaultSimd(Nd, vComplex::Nsimd()),
         GridDefaultMpi()));
   ScalarGrid.set_rb(SpaceTimeGrid::makeFourDimRedBlackGrid(ScalarGrid.get_full()));
@@ -89,12 +89,11 @@ int main(int argc, char **argv) {
   /////////////////////////////////////////////////////////////
 
   // HMC parameters are serialisable
-  TheHMC.Parameters.MD.MDsteps = 10;
+  TheHMC.Parameters.MD.MDsteps = 20;
   TheHMC.Parameters.MD.trajL   = 1.0;
 
   TheHMC.ReadCommandLine(argc, argv);
   TheHMC.Run();
 
   Grid_finalize();
-
+}  // main
-} // main