Split testing

tests/forces/ForceTest.h

@@ -0,0 +1,138 @@
+/*************************************************************************************
+
+    Grid physics library, www.github.com/paboyle/Grid
+
+    Source file: ./tests/forces/ForceTest.h
+
+    Copyright (C) 2022
+
+Author: Peter Boyle <pboyle@bnl.gov>
+
+    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 */
+#pragma once
+
+/////////////////////////////////////////////////////////////////////////////////////////////
+// Finite-difference check of an action's force: refresh, S1 = S(U), step the links by eps
+// along a random momentum P, take the force at the midpoint, step again, S2 = S(U'').
+// The force predicts S2 - S1 to O(eps^3).
+//
+// Runs on a copy of U, so the caller's field is unchanged. Returns S2 - S1 - dSpred for
+// the caller to assert on; halving eps should reduce it by about 8.
+/////////////////////////////////////////////////////////////////////////////////////////////
+template<class Gimpl>
+RealD ForceTest(Action<LatticeGaugeField> &action,LatticeGaugeField & Uin,MomentumFilterBase<LatticeGaugeField> &Filter,RealD eps=0.005)
+{
+  GridBase *UGrid = Uin.Grid();
+
+  std::vector<int> seeds({1,2,3,5});
+  GridSerialRNG            sRNG;         sRNG.SeedFixedIntegers(seeds);
+  GridParallelRNG          RNG4(UGrid);  RNG4.SeedFixedIntegers(seeds);
+
+  LatticeColourMatrix Pmu(UGrid);
+  LatticeGaugeField P(UGrid);
+  LatticeGaugeField UdSdU(UGrid);
+  LatticeGaugeField U(UGrid);
+  U = Uin;
+
+  std::cout << GridLogMessage << "*********************************************************"<<std::endl;
+  std::cout << GridLogMessage << " Force test for "<<action.action_name()<<" eps "<<eps<<std::endl;
+  std::cout << GridLogMessage << "*********************************************************"<<std::endl;
+
+  std::cout << GridLogMessage << "+++++++++++++++++++++++++++++++++++++++++++++++++++++++++"<<std::endl;
+  std::cout << GridLogMessage << " Refresh "<<action.action_name()<<std::endl;
+  std::cout << GridLogMessage << "+++++++++++++++++++++++++++++++++++++++++++++++++++++++++"<<std::endl;
+
+  Gimpl::generate_momenta(P,sRNG,RNG4);
+  Filter.applyFilter(P);
+
+  action.refresh(U,sRNG,RNG4);
+
+  std::cout << GridLogMessage << "+++++++++++++++++++++++++++++++++++++++++++++++++++++++++"<<std::endl;
+  std::cout << GridLogMessage << " Action "<<action.action_name()<<std::endl;
+  std::cout << GridLogMessage << "+++++++++++++++++++++++++++++++++++++++++++++++++++++++++"<<std::endl;
+
+  RealD S1 = action.S(U);
+
+  Gimpl::update_field(P,U,eps);
+
+  std::cout << GridLogMessage << "+++++++++++++++++++++++++++++++++++++++++++++++++++++++++"<<std::endl;
+  std::cout << GridLogMessage << " Derivative "<<action.action_name()<<std::endl;
+  std::cout << GridLogMessage << "+++++++++++++++++++++++++++++++++++++++++++++++++++++++++"<<std::endl;
+  action.deriv(U,UdSdU);
+  UdSdU = Ta(UdSdU);
+  Filter.applyFilter(UdSdU);
+
+  DumpSliceNorm("Force",UdSdU,Nd-1);
+
+  Gimpl::update_field(P,U,eps);
+  std::cout << GridLogMessage << "+++++++++++++++++++++++++++++++++++++++++++++++++++++++++"<<std::endl;
+  std::cout << GridLogMessage << " Action "<<action.action_name()<<std::endl;
+  std::cout << GridLogMessage << "+++++++++++++++++++++++++++++++++++++++++++++++++++++++++"<<std::endl;
+
+  RealD S2 = action.S(U);
+
+  // Use the derivative
+  LatticeComplex dS(UGrid); dS = Zero();
+  for(int mu=0;mu<Nd;mu++){
+    auto UdSdUmu = PeekIndex<LorentzIndex>(UdSdU,mu);
+    Pmu= PeekIndex<LorentzIndex>(P,mu);
+    dS = dS - trace(Pmu*UdSdUmu)*eps*2.0*2.0;
+  }
+  ComplexD dSpred    = sum(dS);
+  RealD diff =  S2-S1-dSpred.real();
+
+  std::cout<< GridLogMessage << "+++++++++++++++++++++++++++++++++++++++++++++++++++++++++"<<std::endl;
+  std::cout<< GridLogMessage << "S1 : "<< S1    <<std::endl;
+  std::cout<< GridLogMessage << "S2 : "<< S2    <<std::endl;
+  std::cout<< GridLogMessage << "dS : "<< S2-S1 <<std::endl;
+  std::cout<< GridLogMessage << "dSpred : "<< dSpred.real() <<std::endl;
+  std::cout<< GridLogMessage << "diff : "<< diff<<std::endl;
+  std::cout<< GridLogMessage << "*********************************************************"<<std::endl;
+  std::cout<< GridLogMessage << "Done" <<std::endl;
+  std::cout << GridLogMessage << "*********************************************************"<<std::endl;
+  return diff;
+}
+
+/////////////////////////////////////////////////////////////////////////////////////////////
+// ForceTest at eps0, eps0/2, ... (neps values). A correct force leaves an O(eps^3)
+// discrepancy, so successive ratios approach 8 as eps shrinks; an error in the force adds
+// an O(eps) part and drives them towards 2. A strongly curved action needs a smaller eps0
+// before the ratios settle. Returns the ratio for the smallest pair.
+/////////////////////////////////////////////////////////////////////////////////////////////
+template<class Gimpl>
+RealD ForceTestScaling(Action<LatticeGaugeField> &action,LatticeGaugeField &U,MomentumFilterBase<LatticeGaugeField> &Filter,const std::string &name,
+                       RealD eps0=0.01,int neps=4)
+{
+  std::vector<RealD> eps(neps);
+  std::vector<RealD> d(neps);
+  for(int i=0;i<neps;i++){
+    eps[i] = eps0/(1<<i);
+    d[i]   = ForceTest<Gimpl>(action,U,Filter,eps[i]);
+  }
+  for(int i=0;i<neps;i++){
+    std::cout << GridLogMessage << name << ": eps " << eps[i] << " discrepancy " << d[i];
+    if ( i > 0 ) {
+      std::cout << "  ratio to previous " << d[i-1]/d[i];
+    }
+    std::cout << std::endl;
+  }
+  RealD scale = d[neps-2]/d[neps-1];
+  std::cout << GridLogMessage << name << ": smallest-eps ratio " << scale << " (expect ~8)" << std::endl;
+  return scale;
+}