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217 lines
7.5 KiB
C++
217 lines
7.5 KiB
C++
/*************************************************************************************
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Grid physics library, www.github.com/paboyle/Grid
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Source file: ./lib/algorithms/iterative/MinimalResidual.h
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Copyright (C) 2015
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Author: Azusa Yamaguchi <ayamaguc@staffmail.ed.ac.uk>
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Author: Peter Boyle <paboyle@ph.ed.ac.uk>
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Author: paboyle <paboyle@ph.ed.ac.uk>
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License along
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with this program; if not, write to the Free Software Foundation, Inc.,
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51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
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See the full license in the file "LICENSE" in the top level distribution
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directory
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*************************************************************************************/
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/* END LEGAL */
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#ifndef GRID_MINIMAL_RESIDUAL_H
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#define GRID_MINIMAL_RESIDUAL_H
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namespace Grid {
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/////////////////////////////////////////////////////////////
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// Base classes for iterative processes based on operators
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// single input vec, single output vec.
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/////////////////////////////////////////////////////////////
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template<class Field> class MinimalResidual : public OperatorFunction<Field> {
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public:
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bool ErrorOnNoConverge; // throw an assert when the MR fails to converge.
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// Defaults true.
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RealD Tolerance;
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Integer MaxIterations;
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Integer IterationsToComplete; // Number of iterations the MR took to finish. Filled in upon completion
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MinimalResidual(RealD tol, Integer maxit, bool err_on_no_conv = true)
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: Tolerance(tol),
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MaxIterations(maxit),
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ErrorOnNoConverge(err_on_no_conv){};
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//! Minimal-residual (MR) algorithm for a generic Linear Operator
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/*! \ingroup invert
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* This subroutine uses the Minimal Residual (MR) algorithm to determine
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* the solution of the set of linear equations. Here we allow M to be
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nonhermitian.
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*
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* M . Psi = src
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*
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* Algorithm:
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*
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* Psi[0] Argument
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* r[0] := src - M . Psi[0] ; Initial residual
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* IF |r[0]| <= RsdCG |src| THEN RETURN; Converged?
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* FOR k FROM 1 TO MaxCG DO MR iterations
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* a[k-1] := <M.r[k-1],r[k-1]> / <M.r[k-1],M.r[k-1]> ;
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* ap[k-1] := MRovpar * a[k] ; Overrelaxtion step
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* Psi[k] += ap[k-1] r[k-1] ; New solution vector
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* r[k] -= ap[k-1] A . r[k-1] ; New residual
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* IF |r[k]| <= RsdCG |src| THEN RETURN; Converged?
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* Arguments:
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* \param M Linear Operator (Read)
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* \param src Source (Read)
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* \param psi Solution (Modify)
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* \param RsdCG MR residual accuracy (Read)
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* \param MRovpar Overrelaxation parameter (Read)
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* \param MaxIterations Maximum MR iterations (Read)
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* Local Variables:
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* r Residual vector
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* cp | r[k] |**2
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* c | r[k-1] |**2
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* k MR iteration counter
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* a a[k]
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* d < M.r[k], M.r[k] >
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* R_Aux Temporary for M.Psi
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* Mr Temporary for M.r
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* Global Variables:
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* MaxIterations Maximum number of MR iterations allowed
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* RsdCG Maximum acceptable MR residual (relative to source)
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*
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* Subroutines:
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*
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* M Apply matrix to vector
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*
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* @{
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*/
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void operator()(LinearOperatorBase<Field> &Linop, const Field &src, Field &psi) {
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psi.checkerboard = src.checkerboard;
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conformable(psi, src);
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Complex a, c;
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RealD d;
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Field Mr(src);
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Field r(src);
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// Initial residual computation & set up
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RealD guess = norm2(psi);
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assert(std::isnan(guess) == 0);
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RealD ssq = norm2(src); // flopcount.addSiteFlops(4*Nc*Ns,s); // stands for "source squared"
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RealD rsd_sq = Tolerance * Tolerance * ssq; // flopcount.addSiteFlops(4*Nc*Ns,s); //
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// stands for "residual squared"
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/* r[0] := src - M . Psi[0] */
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/* r := M . Psi */
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// M(Mr, psi, isign); // flopcount.addFlops(M.nFlops());
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Linop.Op(psi, Mr); // flopcount.addFlops(M.nFlops());
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r = src - Mr; // flopcount.addSiteFlops(2*Nc*Ns,s);
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RealD cp = norm2(r); /* Cp = |r[0]|^2 */
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/* 2 Nc Ns flops */ // flopcount.addSiteFlops(4*Nc*Ns, s);
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// auto cp = norm2(r); /* Cp = |r[0]|^2 */ /* 2 Nc Ns flops */ //
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// flopcount.addSiteFlops(4*Nc*Ns, s);
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if(cp <= rsd_sq) { /* IF |r[0]| <= Tolerance|src| THEN RETURN; */
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return;
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}
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std::cout << GridLogIterative << std::setprecision(4)
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<< "MinimalResidual: k=0 residual " << cp << " target " << rsd_sq << std::endl;
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GridStopWatch LinalgTimer;
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GridStopWatch MatrixTimer;
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GridStopWatch SolverTimer;
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SolverTimer.Start();
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auto k = 0;
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while((k < MaxIterations) && (cp > rsd_sq)) {
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++k;
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/* a[k-1] := < M.r[k-1], r[k-1] >/ < M.r[k-1], M.r[k-1] > ; */
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MatrixTimer.Start();
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// M(Mr, r, isign); /* Mr = M * r */ // flopcount.addFlops(M.nFlops());
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Linop.Op(r, Mr); /* Mr = M * r */ // flopcount.addFlops(M.nFlops());
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MatrixTimer.Stop();
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LinalgTimer.Start();
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c = innerProduct(Mr, r); /* c = < M.r, r > */ // flopcount.addSiteFlops(4*Nc*Ns,s);
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d = norm2(Mr); /* d = | M.r | ** 2 */ // flopcount.addSiteFlops(4*Nc*Ns,s);
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a = c / d;
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// a = a * MRovpar; /* a[k-1] *= MRovpar ; */
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psi = psi + r * a; /* Psi[k] += a[k-1] r[k-1] ; */ // flopcount.addSiteFlops(4*Nc*Ns,s);
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r = r - Mr * a; /* r[k] -= a[k-1] M . r[k-1] ; */ // flopcount.addSiteFlops(4*Nc*Ns,s);
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cp = norm2(r); /* cp = | r[k] |**2 */ // flopcount.addSiteFlops(4*Nc*Ns,s);
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LinalgTimer.Stop();
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std::cout << GridLogIterative << "MinimalResidual: Iteration " << k
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<< " residual " << cp << " target " << rsd_sq << std::endl;
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}
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SolverTimer.Stop();
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IterationsToComplete = k;
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// res.resid = sqrt(cp);
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std::cout << "InvMR: k = " << k << " cp = " << cp << std::endl;
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// flopcount.report("invmr", swatch.getTimeInSeconds());
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std::cout << GridLogMessage << "MinimalResidual Converged on iteration " << k << std::endl;
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std::cout << GridLogMessage << "\tComputed residual " << sqrt(cp / ssq)<<std::endl;
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// std::cout << GridLogMessage << "\tTrue residual " << true_residual<<std::endl;
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// std::cout << GridLogMessage << "\tTarget " << Tolerance << std::endl;
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std::cout << GridLogMessage << "Time breakdown "<<std::endl;
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std::cout << GridLogMessage << "\tElapsed " << SolverTimer.Elapsed() <<std::endl;
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std::cout << GridLogMessage << "\tMatrix " << MatrixTimer.Elapsed() <<std::endl;
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std::cout << GridLogMessage << "\tLinalg " << LinalgTimer.Elapsed() <<std::endl;
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// Compute the actual residual
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{
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// M(Mr, psi, isign);
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Linop.Op(psi, Mr);
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Field tmp = src - Mr;
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// RealD actual_res = norm2(src-Mr);
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RealD actual_res = norm2(tmp);
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// res.resid = sqrt(actual_res);
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}
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if(IterationsToComplete == MaxIterations)
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std::cerr << "Nonconvergence Warning" << std::endl;
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// return res;
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}
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};
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} // namespace Grid
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#endif
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