Updates

tests/debug/Test_mrhs_deflation.cc

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+/*************************************************************************************
+
+    Grid physics library, www.github.com/paboyle/Grid
+
+    Source file: ./tests/debug/Test_mrhs_deflation.cc
+
+    Copyright (C) 2026
+
+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.
+
+    See the full license in the file "LICENSE" in the top level distribution
+    directory
+*************************************************************************************/
+/*  END LEGAL */
+#include <Grid/Grid.h>
+
+// MultiRHSDeflation: the D+1 multiRHS interface (one permutation pass each
+// way) must reproduce the vector-of-D-fields interface bit for bit up to
+// the summation order of the GEMMs.  Random "eigenvectors" and values: the
+// deflation formula G = E (E^dag R)/lambda does not care that they are not
+// eigenpairs of anything.
+
+using namespace Grid;
+
+int main (int argc, char ** argv)
+{
+  Grid_init(&argc,&argv);
+
+  const int nbasis = 8;
+  const int nev    = 12;
+  const int nrhs   = 5;
+
+  typedef iVector<sTComplexD,nbasis> siteVector;
+  typedef Lattice<siteVector>        CoarseVector;
+
+  // Unvectorised D and D+1 coarse grids, as MGCoarseGrids builds them
+  Coordinate latt({1,4,4,4,4});
+  Coordinate simd({1,1,1,1,1});
+  Coordinate mpi = GridDefaultMpi();
+  Coordinate mpi5({1,mpi[0],mpi[1],mpi[2],mpi[3]});
+  GridCartesian Coarse5d(latt,simd,mpi5);
+
+  Coordinate latt6({nrhs,1,4,4,4,4});
+  Coordinate simd6({1,1,1,1,1,1});
+  Coordinate mpi6({1,1,mpi[0],mpi[1],mpi[2],mpi[3]});
+  GridCartesian CoarseMrhs(latt6,simd6,mpi6);
+
+  GridParallelRNG RNG(&Coarse5d); RNG.SeedFixedIntegers(std::vector<int>({1,2,3,4}));
+
+  std::vector<CoarseVector> evec(nev,&Coarse5d);
+  std::vector<RealD>        eval(nev);
+  for(int e=0;e<nev;e++){ random(RNG,evec[e]); eval[e] = 0.5 + 0.1*e; }
+
+  std::vector<CoarseVector> src(nrhs,&Coarse5d), guess(nrhs,&Coarse5d);
+  for(int r=0;r<nrhs;r++) random(RNG,src[r]);
+
+  MultiRHSDeflation<CoarseVector> Deflator;
+  Deflator.ImportEigenBasis(evec,eval);
+
+  // Reference: the vector interface
+  Deflator.DeflateSources(src,guess);
+
+  // The D+1 interface on the same sources
+  CoarseVector src_mrhs(&CoarseMrhs), guess_mrhs(&CoarseMrhs);
+  for(int r=0;r<nrhs;r++) InsertSliceFast(src[r],src_mrhs,r,0);
+  guess_mrhs = Zero();
+  Deflator.DeflateSources(src_mrhs,guess_mrhs);
+
+  RealD worst = 0.0;
+  CoarseVector g(&Coarse5d), d(&Coarse5d);
+  for(int r=0;r<nrhs;r++){
+    ExtractSliceFast(g,guess_mrhs,r,0);
+    d = g - guess[r];
+    RealD rel = std::sqrt(norm2(d)/norm2(guess[r]));
+    std::cout << GridLogMessage << "rhs " << r << " ||guess_mrhs - guess||/||guess|| = " << rel << std::endl;
+    worst = std::max(worst,rel);
+  }
+  std::cout << GridLogMessage << "MultiRHSDeflation D+1 vs vector interface: worst " << worst << std::endl;
+  GRID_ASSERT( worst < 1.0e-12 );
+  std::cout << GridLogMessage << "PASS" << std::endl;
+
+  Grid_finalize();
+  return 0;
+}