PreconditionerDiagonal.cpp

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///////////////////////////////////////////////////////////////////////////////
//
// File: PreconditionerDiagonal.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).
//
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// Description: PreconditionerDiagonal definition
//
///////////////////////////////////////////////////////////////////////////////
 
#include <LibUtilities/BasicUtils/VDmathArray.hpp>
#include <MultiRegions/GlobalLinSysIterativeStaticCond.h>
#include <MultiRegions/GlobalMatrixKey.h>
#include <MultiRegions/PreconditionerDiagonal.h>
#include <cmath>
 
using namespace std;
 
namespace Nektar
{
namespace MultiRegions
{
/**
 * Registers the class with the Factory.
 */
string PreconditionerDiagonal::className =
    GetPreconFactory().RegisterCreatorFunction(
        "Diagonal", PreconditionerDiagonal::create, "Diagonal Preconditioning");
/**
 * @class Preconditioner
 *
 * This class implements diagonal preconditioning for the conjugate
 * gradient matrix solver.
 */
 
PreconditionerDiagonal::PreconditionerDiagonal(
    const std::shared_ptr<GlobalLinSys> &plinsys,
    const AssemblyMapSharedPtr &pLocToGloMap)
    : Preconditioner(plinsys, pLocToGloMap)
{
}
 
void PreconditionerDiagonal::v_InitObject()
{
}
 
void PreconditionerDiagonal::v_BuildPreconditioner()
{
    GlobalSysSolnType solvertype = m_locToGloMap.lock()->GetGlobalSysSolnType();
    if (solvertype == eIterativeFull)
    {
        DiagonalPreconditionerSum();
    }
    else if (solvertype == eIterativeStaticCond ||
             solvertype == eIterativeMultiLevelStaticCond ||
             solvertype == ePETScStaticCond ||
             solvertype == ePETScMultiLevelStaticCond)
    {
        StaticCondDiagonalPreconditionerSum();
    }
    else
    {
        ASSERTL0(0, "Unsupported solver type");
    }
}
 
/**
 * Diagonal preconditioner computed by summing the relevant elements of
 * the local matrix system.
 */
void PreconditionerDiagonal::DiagonalPreconditionerSum()
{
    std::shared_ptr<MultiRegions::ExpList> expList =
        ((m_linsys.lock())->GetLocMat()).lock();
 
    LocalRegions::ExpansionSharedPtr locExpansion;
 
    auto asmMap = m_locToGloMap.lock();
 
    int i, j, n, cnt, gid1, gid2;
    NekDouble sign1, sign2, value;
    int nGlobal = asmMap->GetNumGlobalCoeffs();
    int nDir    = asmMap->GetNumGlobalDirBndCoeffs();
    int nInt    = nGlobal - nDir;
 
    // fill global matrix
    DNekScalMatSharedPtr loc_mat;
    Array<OneD, NekDouble> vOutput(nGlobal, 0.0);
 
    int loc_row;
    int nElmt = expList->GetNumElmts();
    for (n = cnt = 0; n < nElmt; ++n)
    {
        loc_mat = (m_linsys.lock())->GetBlock(n);
        loc_row = loc_mat->GetRows();
 
        for (i = 0; i < loc_row; ++i)
        {
            gid1  = asmMap->GetLocalToGlobalMap(cnt + i) - nDir;
            sign1 = asmMap->GetLocalToGlobalSign(cnt + i);
 
            if (gid1 >= 0)
            {
                for (j = 0; j < loc_row; ++j)
                {
                    gid2  = asmMap->GetLocalToGlobalMap(cnt + j) - nDir;
                    sign2 = asmMap->GetLocalToGlobalSign(cnt + j);
                    if (gid2 == gid1)
                    {
                        // When global matrix is symmetric,
                        // only add the value for the upper
                        // triangular part in order to avoid
                        // entries to be entered twice
                        value = vOutput[gid1 + nDir] +
                                sign1 * sign2 * (*loc_mat)(i, j);
                        vOutput[gid1 + nDir] = value;
                    }
                }
            }
        }
        cnt += loc_row;
    }
 
    // Assemble diagonal contributions across processes
    asmMap->UniversalAssemble(vOutput);
 
    m_diagonals = Array<OneD, NekDouble>(nInt);
    Vmath::Sdiv(nInt, 1.0, &vOutput[nDir], 1, &m_diagonals[0], 1);
}
 
/**
 * Diagonal preconditioner defined as the inverse of the main
 * diagonal of the Schur complement
 *
 */
void PreconditionerDiagonal::StaticCondDiagonalPreconditionerSum()
{
    auto asmMap = m_locToGloMap.lock();
 
    int nGlobalBnd = asmMap->GetNumGlobalBndCoeffs();
    int nDirBnd    = asmMap->GetNumGlobalDirBndCoeffs();
    int rows       = nGlobalBnd - nDirBnd;
 
    Array<OneD, NekDouble> vOutput(nGlobalBnd, 0.0);
 
    // Extract diagonal contributions
    Array<OneD, NekDouble> diagonals = AssembleStaticCondGlobalDiagonals();
    for (unsigned int i = 0; i < rows; ++i)
    {
        vOutput[nDirBnd + i] = diagonals[i];
    }
 
    // Assemble diagonal contributions across processes
    asmMap->UniversalAssembleBnd(vOutput);
 
    m_diagonals = Array<OneD, NekDouble>(rows);
    Vmath::Sdiv(rows, 1.0, &vOutput[nDirBnd], 1, &m_diagonals[0], 1);
}
 
/**
 *
 */
void PreconditionerDiagonal::v_DoPreconditioner(
    const Array<OneD, NekDouble> &pInput, Array<OneD, NekDouble> &pOutput)
{
    auto asmMap = m_locToGloMap.lock();
 
    GlobalSysSolnType solvertype = asmMap->GetGlobalSysSolnType();
 
    int nGlobal = solvertype == eIterativeFull
                      ? asmMap->GetNumGlobalCoeffs()
                      : asmMap->GetNumGlobalBndCoeffs();
    int nDir    = asmMap->GetNumGlobalDirBndCoeffs();
    int nNonDir = nGlobal - nDir;
    Vmath::Vmul(nNonDir, &pInput[0], 1, &m_diagonals[0], 1, &pOutput[0], 1);
}
 
string PreconditionerNull::className =
    GetPreconFactory().RegisterCreatorFunction(
        "Null", PreconditionerNull::create, "No Preconditioning");
 
/**
 * @class Null Preconditioner
 *
 * This class implements no preconditioning for the conjugate
 * gradient matrix solver.
 */
PreconditionerNull::PreconditionerNull(
    const std::shared_ptr<GlobalLinSys> &plinsys,
    const AssemblyMapSharedPtr &pLocToGloMap)
    : Preconditioner(plinsys, pLocToGloMap)
{
}
 
/**
 *
 */
void PreconditionerNull::v_InitObject()
{
}
 
/**
 *
 */
void PreconditionerNull::v_BuildPreconditioner()
{
}
 
/**
 *
 */
void PreconditionerNull::v_DoPreconditioner(
    const Array<OneD, NekDouble> &pInput, Array<OneD, NekDouble> &pOutput)
{
    Vmath::Vcopy(pInput.size(), pInput, 1, pOutput, 1);
}
 
} // namespace MultiRegions
} // namespace Nektar