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Reusable mixed precision wrapper

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Quadro 2021-06-01 13:31:18 -04:00
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Grid/qcd/utils/MixedPrecisionOperatorFunction.h Normal file
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/*************************************************************************************
Grid physics library, www.github.com/paboyle/Grid
Source file:
Copyright (C) 2015-2016
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 */
#pragma once
NAMESPACE_BEGIN(Grid);
template<class FermionOperatorD, class FermionOperatorF, class SchurOperatorD, class SchurOperatorF>
class MixedPrecisionConjugateGradientOperatorFunction : public OperatorFunction<typename FermionOperatorD::FermionField> {
public:
typedef typename FermionOperatorD::FermionField FieldD;
typedef typename FermionOperatorF::FermionField FieldF;
using OperatorFunction<FieldD>::operator();
RealD Tolerance;
RealD InnerTolerance; //Initial tolerance for inner CG. Defaults to Tolerance but can be changed
Integer MaxInnerIterations;
Integer MaxOuterIterations;
GridBase* SinglePrecGrid;
RealD OuterLoopNormMult; //Stop the outer loop and move to a final double prec solve when the residual is OuterLoopNormMult * Tolerance
FermionOperatorF &FermOpF;
FermionOperatorD &FermOpD;;
SchurOperatorF &LinOpF;
SchurOperatorD &LinOpD;
Integer TotalInnerIterations; //Number of inner CG iterations
Integer TotalOuterIterations; //Number of restarts
Integer TotalFinalStepIterations; //Number of CG iterations in final patch-up step
MixedPrecisionConjugateGradientOperatorFunction(RealD tol,
Integer maxinnerit,
Integer maxouterit,
GridBase *_SinglePrecGrid,
FermionOperatorF &_FermOpF,
FermionOperatorD &_FermOpD,
SchurOperatorF &_LinOpF,
SchurOperatorD &_LinOpD) :
LinOpF(_LinOpF),
LinOpD(_LinOpD),
FermOpF(_FermOpF),
FermOpD(_FermOpD),
Tolerance(tol),
InnerTolerance(tol),
MaxInnerIterations(maxinnerit),
MaxOuterIterations(maxouterit),
SinglePrecGrid(_SinglePrecGrid),
OuterLoopNormMult(100.)
{ };
void operator()(LinearOperatorBase<FieldD> &LinOpU, const FieldD &src, FieldD &psi)
{
SchurOperatorD * SchurOpU = static_cast<SchurOperatorD *>(&LinOpU);
// Assumption made in code to extract gauge field
// We could avoid storing LinopD reference alltogether ?
assert(&(SchurOpU->_Mat)==&(LinOpD._Mat));
////////////////////////////////////////////////////////////////////////////////////
// Moving this to a Clone method of fermion operator would allow to duplicate the
// physics parameters and decrease gauge field copies
////////////////////////////////////////////////////////////////////////////////////
auto &Umu_d = FermOpD.GetDoubledGaugeField();
auto &Umu_f = FermOpF.GetDoubledGaugeField();
auto &Umu_fe= FermOpF.GetDoubledGaugeFieldE();
auto &Umu_fo= FermOpF.GetDoubledGaugeFieldO();
precisionChange(Umu_f,Umu_d);
pickCheckerboard(Even,Umu_fe,Umu_f);
pickCheckerboard(Odd ,Umu_fo,Umu_f);
//////////////////////////////////////////////////////////////////////////////////////////
// Make a mixed precision conjugate gradient
//////////////////////////////////////////////////////////////////////////////////////////
// Could assume red black solver here and remove the SinglePrecGrid parameter???
MixedPrecisionConjugateGradient<FieldD,FieldF> MPCG(Tolerance,MaxInnerIterations,MaxOuterIterations,SinglePrecGrid,LinOpF,LinOpD);
std::cout << GridLogMessage << "Calling mixed precision Conjugate Gradient src "<<norm2(src)<< " U "<<norm2(Umu_d) <<std::endl;
psi=Zero();
MPCG(src,psi);
}
};
NAMESPACE_END(Grid);