PreconditionerLinearWithLowEnergy.cpp

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///////////////////////////////////////////////////////////////////////////////
//
// File: PreconditionerLinearWithLowEnergy.cpp
//
// For more information, please see: http://www.nektar.info
//
// The MIT License
//
// Copyright (c) 2006 Division of Applied Mathematics, Brown University (USA),
// Department of Aeronautics, Imperial College London (UK), and Scientific
// Computing and Imaging Institute, University of Utah (USA).
//
// Permission is hereby granted, free of charge, to any person obtaining a
// copy of this software and associated documentation files (the "Software"),
// to deal in the Software without restriction, including without limitation
// the rights to use, copy, modify, merge, publish, distribute, sublicense,
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// Software is furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included
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//
// Description: PreconditionerLinearWithLowEnergy definition
//
///////////////////////////////////////////////////////////////////////////////
 
#include <LocalRegions/MatrixKey.h>
#include <MultiRegions/GlobalMatrixKey.h>
#include <MultiRegions/PreconditionerLinearWithLowEnergy.h>
#include <MultiRegions/PreconditionerLowEnergy.h>
#include <cmath>
 
using namespace std;
 
namespace Nektar::MultiRegions
{
/**
 * Registers the class with the Factory.
 */
 
string PreconditionerLinearWithLowEnergy::className =
    GetPreconFactory().RegisterCreatorFunction(
        "FullLinearSpaceWithLowEnergyBlock",
        PreconditionerLinearWithLowEnergy::create,
        "Full Linear space and low energy block preconditioning");
 
/**
 * @class PreconditionerLinearWithLowEnergy
 *
 * This class implements preconditioning for the conjugate
 * gradient matrix solver.
 */
 
PreconditionerLinearWithLowEnergy::PreconditionerLinearWithLowEnergy(
    const std::shared_ptr<GlobalLinSys> &plinsys,
    const AssemblyMapSharedPtr &pLocToGloMap)
    : Preconditioner(plinsys, pLocToGloMap)
{
}
 
/**
 *
 */
void PreconditionerLinearWithLowEnergy::v_InitObject()
{
    m_linSpacePrecon = GetPreconFactory().CreateInstance(
        "FullLinearSpace", m_linsys.lock(), m_locToGloMap.lock());
    m_lowEnergyPrecon = GetPreconFactory().CreateInstance(
        "LowEnergyBlock", m_linsys.lock(), m_locToGloMap.lock());
 
    // Set up multiplicity array for inverse transposed transformation matrix
    int nDirBnd     = m_locToGloMap.lock()->GetNumGlobalDirBndCoeffs();
    int nGlobHomBnd = m_locToGloMap.lock()->GetNumGlobalBndCoeffs() - nDirBnd;
    int nLocBnd     = m_locToGloMap.lock()->GetNumLocalBndCoeffs();
 
    m_invMultiplicity = Array<OneD, NekDouble>(nGlobHomBnd, 1.0);
    Array<OneD, NekDouble> loc(nLocBnd);
 
    // need to scatter from global array to handle sign changes
    m_locToGloMap.lock()->GlobalToLocalBnd(m_invMultiplicity, loc, nDirBnd);
 
    // Now assemble values back together to get multiplicity
    m_locToGloMap.lock()->AssembleBnd(loc, m_invMultiplicity, nDirBnd);
    Vmath::Sdiv(nGlobHomBnd, 1.0, m_invMultiplicity, 1, m_invMultiplicity, 1);
}
 
/**
 *
 */
void PreconditionerLinearWithLowEnergy::v_DoTransformBasisToLowEnergy(
    Array<OneD, NekDouble> &pInOut)
{
    m_lowEnergyPrecon->DoTransformBasisToLowEnergy(pInOut);
}
 
/**
 *
 */
void PreconditionerLinearWithLowEnergy::v_DoTransformCoeffsFromLowEnergy(
    Array<OneD, NekDouble> &pInput)
{
    m_lowEnergyPrecon->DoTransformCoeffsFromLowEnergy(pInput);
}
 
/**
 *
 */
void PreconditionerLinearWithLowEnergy::v_DoTransformCoeffsToLowEnergy(
    const Array<OneD, NekDouble> &pInput, Array<OneD, NekDouble> &pOutput)
{
    m_lowEnergyPrecon->DoTransformCoeffsToLowEnergy(pInput, pOutput);
}
 
/**
 *
 */
void PreconditionerLinearWithLowEnergy::v_DoTransformBasisFromLowEnergy(
    const Array<OneD, NekDouble> &pInput, Array<OneD, NekDouble> &pOutput)
{
    m_lowEnergyPrecon->DoTransformBasisFromLowEnergy(pInput, pOutput);
}
 
DNekScalMatSharedPtr PreconditionerLinearWithLowEnergy::v_TransformedSchurCompl(
    int n, int offset, const std::shared_ptr<DNekScalMat> &loc_mat)
{
    DNekScalMatSharedPtr returnval;
    returnval = m_lowEnergyPrecon->TransformedSchurCompl(n, offset, loc_mat);
    return returnval;
}
 
/**
 *
 */
void PreconditionerLinearWithLowEnergy::v_BuildPreconditioner()
{
    m_linSpacePrecon->BuildPreconditioner();
    m_lowEnergyPrecon->BuildPreconditioner();
}
 
/**
 *
 */
void PreconditionerLinearWithLowEnergy::v_DoPreconditioner(
    const Array<OneD, NekDouble> &pInput, Array<OneD, NekDouble> &pOutput,
    const bool &isLocal)
{
    ASSERTL0(isLocal == false, "PreconditionerLinearWithLowEnergy"
                               " is only set up for Global iteratives sovles");
    int nDirBndDofs = m_locToGloMap.lock()->GetNumGlobalDirBndCoeffs();
    int nGlobHomBndDofs =
        m_locToGloMap.lock()->GetNumGlobalBndCoeffs() - nDirBndDofs;
    int nLocBndDofs = m_locToGloMap.lock()->GetNumLocalBndCoeffs();
 
    Array<OneD, NekDouble> tmp(nGlobHomBndDofs, 0.0);
 
    Array<OneD, NekDouble> InputLinear(nGlobHomBndDofs);
    Array<OneD, NekDouble> OutputLowEnergy(nGlobHomBndDofs);
    Array<OneD, NekDouble> OutputLinear(nGlobHomBndDofs);
    Array<OneD, NekDouble> local(nLocBndDofs);
 
    // Transform input from low energy to original basis
    Vmath::Vmul(nGlobHomBndDofs, m_invMultiplicity, 1, pInput, 1, OutputLinear,
                1);
    m_locToGloMap.lock()->GlobalToLocalBnd(OutputLinear, local, nDirBndDofs);
    m_lowEnergyPrecon->DoTransformBasisFromLowEnergy(local, local);
    m_locToGloMap.lock()->AssembleBnd(local, InputLinear, nDirBndDofs);
 
    // Apply linear space preconditioner
    m_linSpacePrecon->DoPreconditionerWithNonVertOutput(InputLinear,
                                                        OutputLinear, tmp);
 
    // transform coefficients back to low energy space
    m_locToGloMap.lock()->GlobalToLocalBnd(OutputLinear, local, nDirBndDofs);
    m_lowEnergyPrecon->DoTransformCoeffsToLowEnergy(local, local);
    m_locToGloMap.lock()->LocalBndToGlobal(local, pOutput, nDirBndDofs, false);
 
    // Apply Low Energy preconditioner
    m_lowEnergyPrecon->DoPreconditioner(pInput, OutputLowEnergy);
 
    ASSERTL1(pOutput.size() >= nGlobHomBndDofs, "Output array is not correct");
    Vmath::Vadd(nGlobHomBndDofs, pOutput, 1, OutputLowEnergy, 1, pOutput, 1);
}
 
} // namespace Nektar::MultiRegions