Cabana_Grid_HypreSemiStructuredSolver.hpp

Go to the documentation of this file.

/****************************************************************************
 * Copyright (c) 2018-2023 by the Cabana authors                            *
 * All rights reserved.                                                     *
 *                                                                          *
 * This file is part of the Cabana library. Cabana is distributed under a   *
 * BSD 3-clause license. For the licensing terms see the LICENSE file in    *
 * the top-level directory.                                                 *
 *                                                                          *
 * SPDX-License-Identifier: BSD-3-Clause                                    *
 ****************************************************************************/

#ifndef CABANA_GRID_HYPRESEMISTRUCTUREDSOLVER_HPP
#define CABANA_GRID_HYPRESEMISTRUCTUREDSOLVER_HPP
 
#include <Cabana_Grid_Array.hpp>
#include <Cabana_Grid_GlobalGrid.hpp>
#include <Cabana_Grid_Hypre.hpp>
#include <Cabana_Grid_IndexSpace.hpp>
#include <Cabana_Grid_LocalGrid.hpp>
#include <Cabana_Grid_Types.hpp>
 
#include <HYPRE_config.h>
#include <HYPRE_sstruct_ls.h>
#include <HYPRE_sstruct_mv.h>
#include <HYPRE_struct_ls.h>
#include <HYPRE_struct_mv.h>
 
#include <Kokkos_Core.hpp>
#include <Kokkos_Profiling_ScopedRegion.hpp>
 
#include <array>
#include <memory>
#include <numeric>
#include <sstream>
#include <string>
#include <type_traits>
#include <vector>
 
namespace Cabana
{
namespace Grid
{
 
//---------------------------------------------------------------------------//
template <class Scalar, class EntityType, class MemorySpace>
class HypreSemiStructuredSolver
{
  public:
    using entity_type = EntityType;
    using memory_space = MemorySpace;
    using value_type = Scalar;
    const int object_type = HYPRE_SSTRUCT;
    static_assert( HypreIsCompatibleWithMemorySpace<memory_space>::value,
                   "HYPRE not compatible with solver memory space" );

    template <class ArrayLayout_t>
    HypreSemiStructuredSolver( const ArrayLayout_t& layout, int n_vars,
                               const bool is_preconditioner = false )
        : _comm( layout.localGrid()->globalGrid().comm() )
        , _is_preconditioner( is_preconditioner )
    {
        HYPRE_Init();
 
        static_assert( is_array_layout<ArrayLayout_t>::value,
                       "Must use an array layout" );
        static_assert(
            std::is_same<typename ArrayLayout_t::entity_type,
                         entity_type>::value,
            "Array layout entity type must match solver entity type" );
 
        // Spatial dimension.
        const std::size_t num_space_dim = ArrayLayout_t::num_space_dim;
 
        // Only a single part grid is supported initially
        int n_parts = 1;
        int part = 0;
 
        // Only create data structures if this is not a preconditioner.
        if ( !_is_preconditioner )
        {
            // Create the grid.
            auto error = HYPRE_SStructGridCreate( _comm, num_space_dim, n_parts,
                                                  &_grid );
            checkHypreError( error );
 
            // Get the global index space spanned by the local grid on this
            // rank. Note that the upper bound is not a bound but rather the
            // last index as this is what Hypre wants. Note that we reordered
            // this to KJI from IJK to be consistent with HYPRE ordering. By
            // setting up the grid like this, HYPRE will then want layout-right
            // data indexed as (i,j,k) or (i,j,k,l) which will allow us to
            // directly use Kokkos::deep_copy to move data between arrays and
            // HYPRE data structures.
            auto global_space = layout.indexSpace( Own(), Global() );
            _lower.resize( num_space_dim );
            _upper.resize( num_space_dim );
            for ( std::size_t d = 0; d < num_space_dim; ++d )
            {
                _lower[d] = static_cast<HYPRE_Int>(
                    global_space.min( num_space_dim - d - 1 ) );
                _upper[d] = static_cast<HYPRE_Int>(
                    global_space.max( num_space_dim - d - 1 ) - 1 );
            }
            error = HYPRE_SStructGridSetExtents( _grid, part, _lower.data(),
                                                 _upper.data() );
            checkHypreError( error );
 
            // Get periodicity. Note we invert the order of this to KJI as well.
            const auto& global_grid = layout.localGrid()->globalGrid();
            HYPRE_Int periodic[num_space_dim];
            for ( std::size_t d = 0; d < num_space_dim; ++d )
                periodic[num_space_dim - 1 - d] =
                    global_grid.isPeriodic( d )
                        ? layout.localGrid()->globalGrid().globalNumEntity(
                              EntityType(), d )
                        : 0;
            error = HYPRE_SStructGridSetPeriodic( _grid, part, periodic );
            checkHypreError( error );
 
            // Set the variables on the HYPRE grid
            std::vector<HYPRE_SStructVariable> vartypes;
            vartypes.resize( n_vars );
            for ( int i = 0; i < n_vars; ++i )
            {
                vartypes[i] = HYPRE_SSTRUCT_VARIABLE_CELL;
            }
            error = HYPRE_SStructGridSetVariables( _grid, part, n_vars,
                                                   vartypes.data() );
 
            // Assemble the grid.
            error = HYPRE_SStructGridAssemble( _grid );
            checkHypreError( error );
 
            // Allocate LHS and RHS vectors and initialize to zero. Note that we
            // are fixing the views under these vectors to layout-right.
 
            std::array<long, num_space_dim + 1> reorder_size;
            for ( std::size_t d = 0; d < num_space_dim; ++d )
            {
                reorder_size[d] = global_space.extent( d );
            }
            reorder_size.back() = n_vars;
            IndexSpace<num_space_dim + 1> reorder_space( reorder_size );
            auto vector_values =
                createView<HYPRE_Complex, Kokkos::LayoutRight, memory_space>(
                    "vector_values0", reorder_space );
            Kokkos::deep_copy( vector_values, 0.0 );
 
            _stencils.resize( n_vars );
            _stencil_size.resize( n_vars );
            _stencil_index.resize( n_vars,
                                   std::vector<unsigned>( n_vars + 1 ) );
 
            error = HYPRE_SStructVectorCreate( _comm, _grid, &_b );
            checkHypreError( error );
            error = HYPRE_SStructVectorSetObjectType( _b, object_type );
            checkHypreError( error );
            error = HYPRE_SStructVectorInitialize( _b );
            checkHypreError( error );
            for ( int i = 0; i < n_vars; ++i )
            {
                error = HYPRE_SStructVectorSetBoxValues(
                    _b, part, _lower.data(), _upper.data(), i,
                    vector_values.data() );
                checkHypreError( error );
            }
            error = HYPRE_SStructVectorAssemble( _b );
            checkHypreError( error );
 
            error = HYPRE_SStructVectorCreate( _comm, _grid, &_x );
            checkHypreError( error );
            error = HYPRE_SStructVectorSetObjectType( _x, object_type );
            checkHypreError( error );
            error = HYPRE_SStructVectorInitialize( _x );
            checkHypreError( error );
            for ( int i = 0; i < n_vars; ++i )
            {
                error = HYPRE_SStructVectorSetBoxValues(
                    _x, part, _lower.data(), _upper.data(), i,
                    vector_values.data() );
                checkHypreError( error );
            }
            checkHypreError( error );
            error = HYPRE_SStructVectorAssemble( _x );
            checkHypreError( error );
        }
    }
 
    // Destructor.
    virtual ~HypreSemiStructuredSolver()
    {
        // We only make data if this is not a preconditioner.
        if ( !_is_preconditioner )
        {
            HYPRE_SStructVectorDestroy( _x );
            HYPRE_SStructVectorDestroy( _b );
            HYPRE_SStructMatrixDestroy( _A );
            for ( std::size_t i = 0; i < _stencils.size(); ++i )
            {
                HYPRE_SStructStencilDestroy( _stencils[i] );
            }
            HYPRE_SStructGridDestroy( _grid );
            HYPRE_SStructGraphDestroy( _graph );
 
            HYPRE_Finalize();
        }
    }

    bool isPreconditioner() const { return _is_preconditioner; }

    void createMatrixStencil( int NumSpaceDim, int var = 0, int n_vars = 3,
                              std::vector<unsigned> stencil_length = { 7, 7,
                                                                       7 } )
    {
        // This function is only valid for non-preconditioners.
        if ( _is_preconditioner )
            throw std::logic_error(
                "Cannot call createMatrixStencil() on preconditioners" );
 
        // Generate the stencil indexing
        unsigned index = 0;
        for ( int i = 0; i < n_vars; ++i )
        {
            _stencil_index[var][i] = index;
            index += stencil_length[i];
        }
        _stencil_index[var][n_vars] = index;
 
        // Create the stencil.
        _stencil_size[var] = index;
        auto error = HYPRE_SStructStencilCreate(
            NumSpaceDim, _stencil_size[var], &_stencils[var] );
        checkHypreError( error );
    }

    template <std::size_t NumSpaceDim>
    void
    setMatrixStencil( const std::vector<std::array<int, NumSpaceDim>>& stencil,
                      int var = 0, int dep = 0 )
    {
        // This function is only valid for non-preconditioners.
        if ( _is_preconditioner )
            throw std::logic_error(
                "Cannot call setMatrixStencil() on preconditioners" );
 
        std::array<HYPRE_Int, NumSpaceDim> offset;
 
        auto index = _stencil_index[var][dep];
        for ( unsigned n = index; n < index + stencil.size(); ++n )
        {
            for ( std::size_t d = 0; d < NumSpaceDim; ++d )
                offset[d] = stencil[n - index][d];
            auto error = HYPRE_SStructStencilSetEntry( _stencils[var], n,
                                                       offset.data(), dep );
            checkHypreError( error );
        }
    }

    void setSolverGraph( int n_vars )
    {
        // This function is only valid for non-preconditioners.
        if ( _is_preconditioner )
            throw std::logic_error(
                "Cannot call setSolverGraph() on preconditioners" );
 
        int part = 0;
 
        // Setup the Graph for the non-zero structure of the matrix
        // Create the graph with hypre
        auto error = HYPRE_SStructGraphCreate( _comm, _grid, &_graph );
        checkHypreError( error );
 
        // Set up the object type
        error = HYPRE_SStructGraphSetObjectType( _graph, object_type );
        checkHypreError( error );
 
        // Set the stencil to the graph
        for ( int i = 0; i < n_vars; ++i )
        {
            error =
                HYPRE_SStructGraphSetStencil( _graph, part, i, _stencils[i] );
            checkHypreError( error );
        }
 
        // Assemble the graph
        error = HYPRE_SStructGraphAssemble( _graph );
        checkHypreError( error );
 
        // Create the matrix. must be done after graph is assembled
        error = HYPRE_SStructMatrixCreate( _comm, _graph, &_A );
        checkHypreError( error );
 
        // Set the SStruct matrix object type
        error = HYPRE_SStructMatrixSetObjectType( _A, object_type );
        checkHypreError( error );
 
        // Prepare the matrix for setting values
        error = HYPRE_SStructMatrixInitialize( _A );
        checkHypreError( error );
    }

    template <class Array_t>
    void setMatrixValues( const Array_t& values, int v_x, int v_h )
    {
        static_assert( is_array<Array_t>::value, "Must use an array" );
        static_assert(
            std::is_same<typename Array_t::entity_type, entity_type>::value,
            "Array entity type must match solver entity type" );
        static_assert(
            std::is_same<typename Array_t::memory_space, MemorySpace>::value,
            "Array device type and solver device type are different." );
 
        static_assert(
            std::is_same<typename Array_t::value_type, value_type>::value,
            "Array value type and solver value type are different." );
 
        // This function is only valid for non-preconditioners.
        if ( _is_preconditioner )
            throw std::logic_error(
                "Cannot call setMatrixValues() on preconditioners" );
 
        int index_size =
            _stencil_index[v_h][v_x + 1] - _stencil_index[v_h][v_x];
 
        // Ensure the values array matches up in dimension with the stencil size
        if ( values.layout()->dofsPerEntity() !=
             static_cast<int>( index_size ) )
            throw std::runtime_error(
                "Cabana::Grid::HypreSemiStructuredSolver::setMatrixValues: "
                "Number of matrix values does not match stencil size" );
 
        // Spatial dimension.
        const std::size_t num_space_dim = Array_t::num_space_dim;
 
        int part = 0;
 
        // Copy the matrix entries into HYPRE. The HYPRE layout is fixed as
        // layout-right.
        auto owned_space = values.layout()->indexSpace( Own(), Local() );
        std::array<long, num_space_dim + 1> reorder_size;
        for ( std::size_t d = 0; d < num_space_dim; ++d )
        {
            reorder_size[d] = owned_space.extent( d );
        }
 
        reorder_size.back() = index_size;
        IndexSpace<num_space_dim + 1> reorder_space( reorder_size );
        auto a_values =
            createView<HYPRE_Complex, Kokkos::LayoutRight, memory_space>(
                "a_values", reorder_space );
 
        auto values_subv = createSubview( values.view(), owned_space );
        Kokkos::deep_copy( a_values, values_subv );
 
        // Insert values into the HYPRE matrix.
        std::vector<HYPRE_Int> indices( index_size );
        int start = _stencil_index[v_h][v_x];
        std::iota( indices.begin(), indices.end(), start );
        auto error = HYPRE_SStructMatrixSetBoxValues(
            _A, part, _lower.data(), _upper.data(), v_h, indices.size(),
            indices.data(), a_values.data() );
        checkHypreError( error );
    }

    void printMatrix( const char* prefix )
    {
        HYPRE_SStructMatrixPrint( prefix, _A, 0 );
    }

    void printLHS( const char* prefix )
    {
        HYPRE_SStructVectorPrint( prefix, _x, 0 );
    }

    void printRHS( const char* prefix )
    {
        HYPRE_SStructVectorPrint( prefix, _b, 0 );
    }

    void setTolerance( const double tol ) { this->setToleranceImpl( tol ); }

    void setMaxIter( const int max_iter ) { this->setMaxIterImpl( max_iter ); }

    void setPrintLevel( const int print_level )
    {
        this->setPrintLevelImpl( print_level );
    }

    void
    setPreconditioner( const std::shared_ptr<HypreSemiStructuredSolver<
                           Scalar, EntityType, MemorySpace>>& preconditioner )
    {
        // This function is only valid for non-preconditioners.
        if ( _is_preconditioner )
            throw std::logic_error(
                "Cannot call setPreconditioner() on a preconditioner" );
 
        // Only a preconditioner can be used as a preconditioner.
        if ( !preconditioner->isPreconditioner() )
            throw std::logic_error( "Not a preconditioner" );
 
        _preconditioner = preconditioner;
        this->setPreconditionerImpl( *_preconditioner );
    }

    void setup()
    {
        // This function is only valid for non-preconditioners.
        if ( _is_preconditioner )
            throw std::logic_error( "Cannot call setup() on preconditioners" );
 
        auto error = HYPRE_SStructMatrixAssemble( _A );
        checkHypreError( error );
 
        this->setupImpl();
    }

    template <class Array_t>
    void solve( const Array_t& b, Array_t& x, int n_vars = 3 )
    {
        Kokkos::Profiling::ScopedRegion region(
            "Cabana::Grid::HypreSemiStructuredSolver::solve" );
 
        static_assert( is_array<Array_t>::value, "Must use an array" );
        static_assert(
            std::is_same<typename Array_t::entity_type, entity_type>::value,
            "Array entity type must match solver entity type" );
        static_assert(
            std::is_same<typename Array_t::memory_space, MemorySpace>::value,
            "Array device type and solver device type are different." );
 
        static_assert(
            std::is_same<typename Array_t::value_type, value_type>::value,
            "Array value type and solver value type are different." );
 
        // This function is only valid for non-preconditioners.
        if ( _is_preconditioner )
            throw std::logic_error( "Cannot call solve() on preconditioners" );
 
        // Spatial dimension.
        const std::size_t num_space_dim = Array_t::num_space_dim;
 
        int part = 0;
 
        // Copy the RHS into HYPRE. The HYPRE layout is fixed as layout-right.
        auto owned_space = b.layout()->indexSpace( Own(), Local() );
        std::array<long, num_space_dim + 1> reorder_min;
        std::array<long, num_space_dim + 1> reorder_max;
        for ( std::size_t d = 0; d < num_space_dim; ++d )
        {
            reorder_min[d] = owned_space.min( d );
            reorder_max[d] = owned_space.max( d );
        }
 
        // Insert b values into the HYPRE vector.
        // The process of creating the view and then deep copying each
        // variable is functional, but we should avoid this process
        // for performance if possible
        int error;
        for ( int var = 0; var < n_vars; ++var )
        {
            reorder_min.back() = var;
            reorder_max.back() = var + 1;
 
            IndexSpace<num_space_dim + 1> reorder_space( reorder_min,
                                                         reorder_max );
            auto b_values =
                createView<HYPRE_Complex, Kokkos::LayoutRight, memory_space>(
                    "vector_values", reorder_space );
            // Extract one variable at at time.
            auto b_subv = createSubview( b.view(), reorder_space );
 
            Kokkos::deep_copy( b_values, b_subv );
            error = HYPRE_SStructVectorSetBoxValues(
                _b, part, _lower.data(), _upper.data(), var, b_values.data() );
            checkHypreError( error );
        }
 
        error = HYPRE_SStructVectorAssemble( _b );
        checkHypreError( error );
 
        // Solve the problem
        this->solveImpl();
 
        // Extract the solution from the LHS
        for ( int var = 0; var < n_vars; ++var )
        {
            reorder_min.back() = var;
            reorder_max.back() = var + 1;
 
            IndexSpace<num_space_dim + 1> reorder_space( reorder_min,
                                                         reorder_max );
            auto x_values =
                createView<HYPRE_Complex, Kokkos::LayoutRight, memory_space>(
                    "vector_values", reorder_space );
 
            // Extract one variable at at time.
            // Use a pair here to retain the view rank.
 
            error = HYPRE_SStructVectorGetBoxValues(
                _x, part, _lower.data(), _upper.data(), var, x_values.data() );
            checkHypreError( error );
 
            // Copy the HYPRE solution to the LHS.
            auto x_subv = createSubview( x.view(), reorder_space );
            Kokkos::deep_copy( x_subv, x_values );
        }
    }

    int getNumIter() { return this->getNumIterImpl(); }

    double getFinalRelativeResidualNorm()
    {
        return this->getFinalRelativeResidualNormImpl();
    }

    virtual HYPRE_SStructSolver getHypreSolver() const = 0;
    virtual HYPRE_PtrToSStructSolverFcn getHypreSetupFunction() const = 0;
    virtual HYPRE_PtrToSStructSolverFcn getHypreSolveFunction() const = 0;
 
  protected:
    virtual void setToleranceImpl( const double tol ) = 0;

    virtual void setMaxIterImpl( const int max_iter ) = 0;

    virtual void setPrintLevelImpl( const int print_level ) = 0;

    virtual void setupImpl() = 0;

    virtual void solveImpl() = 0;

    virtual int getNumIterImpl() = 0;

    virtual double getFinalRelativeResidualNormImpl() = 0;

    virtual void setPreconditionerImpl(
        const HypreSemiStructuredSolver<Scalar, EntityType, MemorySpace>&
            preconditioner ) = 0;

    void checkHypreError( const int error ) const
    {
        if ( error > 0 )
        {
            char error_msg[256];
            HYPRE_DescribeError( error, error_msg );
            std::stringstream out;
            out << "HYPRE semi-structured solver error: ";
            out << error << " " << error_msg;
            HYPRE_ClearError( error );
            throw std::runtime_error( out.str() );
        }
    }

    HYPRE_SStructMatrix _A;
    HYPRE_SStructVector _b;
    HYPRE_SStructVector _x;
 
  private:
    MPI_Comm _comm;
    bool _is_preconditioner;
    HYPRE_SStructGrid _grid;
    std::vector<HYPRE_Int> _lower;
    std::vector<HYPRE_Int> _upper;
    std::vector<HYPRE_SStructStencil> _stencils;
    HYPRE_SStructGraph _graph;
    std::vector<unsigned> _stencil_size;
    std::vector<std::vector<unsigned>> _stencil_index;
    std::shared_ptr<HypreSemiStructuredSolver<Scalar, EntityType, MemorySpace>>
        _preconditioner;
};
 
//---------------------------------------------------------------------------//
template <class Scalar, class EntityType, class MemorySpace>
class HypreSemiStructPCG
    : public HypreSemiStructuredSolver<Scalar, EntityType, MemorySpace>
{
  public:
    using base_type =
        HypreSemiStructuredSolver<Scalar, EntityType, MemorySpace>;
    template <class ArrayLayout_t>
    HypreSemiStructPCG( const ArrayLayout_t& layout, int n_vars,
                        const bool is_preconditioner = false )
        : base_type( layout, n_vars, is_preconditioner )
    {
        if ( is_preconditioner )
            throw std::logic_error(
                "HYPRE PCG cannot be used as a preconditioner" );
 
        auto error = HYPRE_SStructPCGCreate(
            layout.localGrid()->globalGrid().comm(), &_solver );
        this->checkHypreError( error );
 
        HYPRE_SStructPCGSetTwoNorm( _solver, 1 );
    }
 
    ~HypreSemiStructPCG() { HYPRE_SStructPCGDestroy( _solver ); }
 
    // PCG SETTINGS

    void setAbsoluteTol( const double tol )
    {
        auto error = HYPRE_SStructPCGSetAbsoluteTol( _solver, tol );
        this->checkHypreError( error );
    }

    void setRelChange( const int rel_change )
    {
        auto error = HYPRE_SStructPCGSetRelChange( _solver, rel_change );
        this->checkHypreError( error );
    }

    void setLogging( const int logging )
    {
        auto error = HYPRE_SStructPCGSetLogging( _solver, logging );
        this->checkHypreError( error );
    }
 
    HYPRE_SStructSolver getHypreSolver() const override { return _solver; }
    HYPRE_PtrToSStructSolverFcn getHypreSetupFunction() const override
    {
        return HYPRE_SStructPCGSetup;
    }
    HYPRE_PtrToSStructSolverFcn getHypreSolveFunction() const override
    {
        return HYPRE_SStructPCGSolve;
    }
 
  protected:
    void setToleranceImpl( const double tol ) override
    {
        auto error = HYPRE_SStructPCGSetTol( _solver, tol );
        this->checkHypreError( error );
    }
 
    void setMaxIterImpl( const int max_iter ) override
    {
        auto error = HYPRE_SStructPCGSetMaxIter( _solver, max_iter );
        this->checkHypreError( error );
    }
 
    void setPrintLevelImpl( const int print_level ) override
    {
        auto error = HYPRE_SStructPCGSetPrintLevel( _solver, print_level );
        this->checkHypreError( error );
    }
 
    void setupImpl() override
    {
        auto error = HYPRE_SStructPCGSetup( _solver, _A, _b, _x );
        this->checkHypreError( error );
    }
 
    void solveImpl() override
    {
        auto error = HYPRE_SStructPCGSolve( _solver, _A, _b, _x );
        this->checkHypreError( error );
    }
 
    int getNumIterImpl() override
    {
        HYPRE_Int num_iter;
        auto error = HYPRE_SStructPCGGetNumIterations( _solver, &num_iter );
        this->checkHypreError( error );
        return num_iter;
    }
 
    double getFinalRelativeResidualNormImpl() override
    {
        HYPRE_Real norm;
        auto error =
            HYPRE_SStructPCGGetFinalRelativeResidualNorm( _solver, &norm );
        this->checkHypreError( error );
        return norm;
    }
 
    void setPreconditionerImpl(
        const HypreSemiStructuredSolver<Scalar, EntityType, MemorySpace>&
            preconditioner ) override
    {
        auto error = HYPRE_SStructPCGSetPrecond(
            _solver, preconditioner.getHypreSolveFunction(),
            preconditioner.getHypreSetupFunction(),
            preconditioner.getHypreSolver() );
        this->checkHypreError( error );
    }
 
  private:
    HYPRE_SStructSolver _solver;
    using base_type::_A;
    using base_type::_b;
    using base_type::_x;
};
 
//---------------------------------------------------------------------------//
template <class Scalar, class EntityType, class MemorySpace>
class HypreSemiStructGMRES
    : public HypreSemiStructuredSolver<Scalar, EntityType, MemorySpace>
{
  public:
    using base_type =
        HypreSemiStructuredSolver<Scalar, EntityType, MemorySpace>;
    template <class ArrayLayout_t>
    HypreSemiStructGMRES( const ArrayLayout_t& layout, int n_vars,
                          const bool is_preconditioner = false )
        : base_type( layout, n_vars, is_preconditioner )
    {
        if ( is_preconditioner )
            throw std::logic_error(
                "HYPRE GMRES cannot be used as a preconditioner" );
 
        auto error = HYPRE_SStructGMRESCreate(
            layout.localGrid()->globalGrid().comm(), &_solver );
        this->checkHypreError( error );
    }
 
    ~HypreSemiStructGMRES() { HYPRE_SStructGMRESDestroy( _solver ); }
 
    // GMRES SETTINGS

    void setAbsoluteTol( const double tol )
    {
        auto error = HYPRE_SStructGMRESSetAbsoluteTol( _solver, tol );
        this->checkHypreError( error );
    }

    void setKDim( const int k_dim )
    {
        auto error = HYPRE_SStructGMRESSetKDim( _solver, k_dim );
        this->checkHypreError( error );
    }

    void setLogging( const int logging )
    {
        auto error = HYPRE_SStructGMRESSetLogging( _solver, logging );
        this->checkHypreError( error );
    }
 
    HYPRE_SStructSolver getHypreSolver() const override { return _solver; }
    HYPRE_PtrToSStructSolverFcn getHypreSetupFunction() const override
    {
        return HYPRE_SStructGMRESSetup;
    }
    HYPRE_PtrToSStructSolverFcn getHypreSolveFunction() const override
    {
        return HYPRE_SStructGMRESSolve;
    }
 
  protected:
    void setToleranceImpl( const double tol ) override
    {
        auto error = HYPRE_SStructGMRESSetTol( _solver, tol );
        this->checkHypreError( error );
    }
 
    void setMaxIterImpl( const int max_iter ) override
    {
        auto error = HYPRE_SStructGMRESSetMaxIter( _solver, max_iter );
        this->checkHypreError( error );
    }
 
    void setPrintLevelImpl( const int print_level ) override
    {
        auto error = HYPRE_SStructGMRESSetPrintLevel( _solver, print_level );
        this->checkHypreError( error );
    }
 
    void setupImpl() override
    {
        auto error = HYPRE_SStructGMRESSetup( _solver, _A, _b, _x );
        this->checkHypreError( error );
    }
 
    void solveImpl() override
    {
        auto error = HYPRE_SStructGMRESSolve( _solver, _A, _b, _x );
        this->checkHypreError( error );
    }
 
    int getNumIterImpl() override
    {
        HYPRE_Int num_iter;
        auto error = HYPRE_SStructGMRESGetNumIterations( _solver, &num_iter );
        this->checkHypreError( error );
        return num_iter;
    }
 
    double getFinalRelativeResidualNormImpl() override
    {
        HYPRE_Real norm;
        auto error =
            HYPRE_SStructGMRESGetFinalRelativeResidualNorm( _solver, &norm );
        this->checkHypreError( error );
        return norm;
    }
 
    void setPreconditionerImpl(
        const HypreSemiStructuredSolver<Scalar, EntityType, MemorySpace>&
            preconditioner ) override
    {
        auto error = HYPRE_SStructGMRESSetPrecond(
            _solver, preconditioner.getHypreSolveFunction(),
            preconditioner.getHypreSetupFunction(),
            preconditioner.getHypreSolver() );
        this->checkHypreError( error );
    }
 
  private:
    HYPRE_SStructSolver _solver;
    using base_type::_A;
    using base_type::_b;
    using base_type::_x;
};
 
//---------------------------------------------------------------------------//
template <class Scalar, class EntityType, class MemorySpace>
class HypreSemiStructBiCGSTAB
    : public HypreSemiStructuredSolver<Scalar, EntityType, MemorySpace>
{
  public:
    using base_type =
        HypreSemiStructuredSolver<Scalar, EntityType, MemorySpace>;
    template <class ArrayLayout_t>
    HypreSemiStructBiCGSTAB( const ArrayLayout_t& layout,
                             const bool is_preconditioner = false,
                             int n_vars = 3 )
        : base_type( layout, n_vars, is_preconditioner )
    {
        if ( is_preconditioner )
            throw std::logic_error(
                "HYPRE BiCGSTAB cannot be used as a preconditioner" );
 
        auto error = HYPRE_SStructBiCGSTABCreate(
            layout.localGrid()->globalGrid().comm(), &_solver );
        this->checkHypreError( error );
    }
 
    ~HypreSemiStructBiCGSTAB() { HYPRE_SStructBiCGSTABDestroy( _solver ); }
 
    // BiCGSTAB SETTINGS

    void setAbsoluteTol( const double tol )
    {
        auto error = HYPRE_SStructBiCGSTABSetAbsoluteTol( _solver, tol );
        this->checkHypreError( error );
    }

    void setLogging( const int logging )
    {
        auto error = HYPRE_SStructBiCGSTABSetLogging( _solver, logging );
        this->checkHypreError( error );
    }
 
    HYPRE_SStructSolver getHypreSolver() const override { return _solver; }
    HYPRE_PtrToSStructSolverFcn getHypreSetupFunction() const override
    {
        return HYPRE_SStructBiCGSTABSetup;
    }
    HYPRE_PtrToSStructSolverFcn getHypreSolveFunction() const override
    {
        return HYPRE_SStructBiCGSTABSolve;
    }
 
  protected:
    void setToleranceImpl( const double tol ) override
    {
        auto error = HYPRE_SStructBiCGSTABSetTol( _solver, tol );
        this->checkHypreError( error );
    }
 
    void setMaxIterImpl( const int max_iter ) override
    {
        auto error = HYPRE_SStructBiCGSTABSetMaxIter( _solver, max_iter );
        this->checkHypreError( error );
    }
 
    void setPrintLevelImpl( const int print_level ) override
    {
        auto error = HYPRE_SStructBiCGSTABSetPrintLevel( _solver, print_level );
        this->checkHypreError( error );
    }
 
    void setupImpl() override
    {
        auto error = HYPRE_SStructBiCGSTABSetup( _solver, _A, _b, _x );
        this->checkHypreError( error );
    }
 
    void solveImpl() override
    {
        auto error = HYPRE_SStructBiCGSTABSolve( _solver, _A, _b, _x );
        this->checkHypreError( error );
    }
 
    int getNumIterImpl() override
    {
        HYPRE_Int num_iter;
        auto error =
            HYPRE_SStructBiCGSTABGetNumIterations( _solver, &num_iter );
        this->checkHypreError( error );
        return num_iter;
    }
 
    double getFinalRelativeResidualNormImpl() override
    {
        HYPRE_Real norm;
        auto error =
            HYPRE_SStructBiCGSTABGetFinalRelativeResidualNorm( _solver, &norm );
        this->checkHypreError( error );
        return norm;
    }
 
    void setPreconditionerImpl(
        const HypreSemiStructuredSolver<Scalar, EntityType, MemorySpace>&
            preconditioner ) override
    {
        auto error = HYPRE_SStructBiCGSTABSetPrecond(
            _solver, preconditioner.getHypreSolveFunction(),
            preconditioner.getHypreSetupFunction(),
            preconditioner.getHypreSolver() );
        this->checkHypreError( error );
    }
 
  private:
    HYPRE_SStructSolver _solver;
    using base_type::_A;
    using base_type::_b;
    using base_type::_x;
};
 
//---------------------------------------------------------------------------//
template <class Scalar, class EntityType, class MemorySpace>
class HypreSemiStructDiagonal
    : public HypreSemiStructuredSolver<Scalar, EntityType, MemorySpace>
{
  public:
    using base_type =
        HypreSemiStructuredSolver<Scalar, EntityType, MemorySpace>;
    template <class ArrayLayout_t>
    HypreSemiStructDiagonal( const ArrayLayout_t& layout,
                             const bool is_preconditioner = false,
                             int n_vars = 3 )
        : base_type( layout, n_vars, is_preconditioner )
    {
        if ( !is_preconditioner )
            throw std::logic_error(
                "Diagonal preconditioner cannot be used as a solver" );
    }
 
    HYPRE_SStructSolver getHypreSolver() const override { return nullptr; }
    HYPRE_PtrToSStructSolverFcn getHypreSetupFunction() const override
    {
        return HYPRE_SStructDiagScaleSetup;
    }
    HYPRE_PtrToSStructSolverFcn getHypreSolveFunction() const override
    {
        return HYPRE_SStructDiagScale;
    }
 
  protected:
    void setToleranceImpl( const double ) override
    {
        throw std::logic_error(
            "Diagonal preconditioner cannot be used as a solver" );
    }
 
    void setMaxIterImpl( const int ) override
    {
        throw std::logic_error(
            "Diagonal preconditioner cannot be used as a solver" );
    }
 
    void setPrintLevelImpl( const int ) override
    {
        throw std::logic_error(
            "Diagonal preconditioner cannot be used as a solver" );
    }
 
    void setupImpl() override
    {
        throw std::logic_error(
            "Diagonal preconditioner cannot be used as a solver" );
    }
 
    void solveImpl() override
    {
        throw std::logic_error(
            "Diagonal preconditioner cannot be used as a solver" );
    }
 
    int getNumIterImpl() override
    {
        throw std::logic_error(
            "Diagonal preconditioner cannot be used as a solver" );
    }
 
    double getFinalRelativeResidualNormImpl() override
    {
        throw std::logic_error(
            "Diagonal preconditioner cannot be used as a solver" );
    }
 
    void setPreconditionerImpl(
        const HypreSemiStructuredSolver<Scalar, EntityType, MemorySpace>& )
        override
    {
        throw std::logic_error(
            "Diagonal preconditioner does not support preconditioning." );
    }
};
 
//---------------------------------------------------------------------------//
// Builders
//---------------------------------------------------------------------------//
template <class Scalar, class MemorySpace, class ArrayLayout_t>
std::shared_ptr<HypreSemiStructPCG<Scalar, typename ArrayLayout_t::entity_type,
                                   MemorySpace>>
createHypreSemiStructPCG( const ArrayLayout_t& layout,
                          const bool is_preconditioner = false, int n_vars = 3 )
{
    static_assert( is_array_layout<ArrayLayout_t>::value,
                   "Must use an array layout" );
    return std::make_shared<HypreSemiStructPCG<
        Scalar, typename ArrayLayout_t::entity_type, MemorySpace>>(
        layout, n_vars, is_preconditioner );
}

template <class Scalar, class MemorySpace, class ArrayLayout_t>
std::shared_ptr<HypreSemiStructGMRES<
    Scalar, typename ArrayLayout_t::entity_type, MemorySpace>>
createHypreSemiStructGMRES( const ArrayLayout_t& layout,
                            const bool is_preconditioner = false,
                            int n_vars = 3 )
{
    static_assert( is_array_layout<ArrayLayout_t>::value,
                   "Must use an array layout" );
    return std::make_shared<HypreSemiStructGMRES<
        Scalar, typename ArrayLayout_t::entity_type, MemorySpace>>(
        layout, n_vars, is_preconditioner );
}

template <class Scalar, class MemorySpace, class ArrayLayout_t>
std::shared_ptr<HypreSemiStructBiCGSTAB<
    Scalar, typename ArrayLayout_t::entity_type, MemorySpace>>
createHypreSemiStructBiCGSTAB( const ArrayLayout_t& layout,
                               const bool is_preconditioner = false,
                               int n_vars = 3 )
{
    static_assert( is_array_layout<ArrayLayout_t>::value,
                   "Must use an array layout" );
    return std::make_shared<HypreSemiStructBiCGSTAB<
        Scalar, typename ArrayLayout_t::entity_type, MemorySpace>>(
        layout, is_preconditioner, n_vars );
}

template <class Scalar, class MemorySpace, class ArrayLayout_t>
std::shared_ptr<HypreSemiStructDiagonal<
    Scalar, typename ArrayLayout_t::entity_type, MemorySpace>>
createHypreSemiStructDiagonal( const ArrayLayout_t& layout,
                               const bool is_preconditioner = false,
                               int n_vars = 3 )
{
    static_assert( is_array_layout<ArrayLayout_t>::value,
                   "Must use an array layout" );
    return std::make_shared<HypreSemiStructDiagonal<
        Scalar, typename ArrayLayout_t::entity_type, MemorySpace>>(
        layout, is_preconditioner, n_vars );
}
 
//---------------------------------------------------------------------------//
// Factory
//---------------------------------------------------------------------------//
template <class Scalar, class MemorySpace, class ArrayLayout_t>
std::shared_ptr<HypreSemiStructuredSolver<
    Scalar, typename ArrayLayout_t::entity_type, MemorySpace>>
createHypreSemiStructuredSolver( const std::string& solver_type,
                                 const ArrayLayout_t& layout,
                                 const bool is_preconditioner = false,
                                 int n_vars = 3 )
{
    static_assert( is_array_layout<ArrayLayout_t>::value,
                   "Must use an array layout" );
 
    if ( "PCG" == solver_type )
        return createHypreSemiStructPCG<Scalar, MemorySpace>(
            layout, is_preconditioner, n_vars );
    else if ( "GMRES" == solver_type )
        return createHypreSemiStructGMRES<Scalar, MemorySpace>(
            layout, is_preconditioner, n_vars );
    else if ( "BiCGSTAB" == solver_type )
        return createHypreSemiStructBiCGSTAB<Scalar, MemorySpace>(
            layout, is_preconditioner, n_vars );
    else if ( "Diagonal" == solver_type )
        return createHypreSemiStructDiagonal<Scalar, MemorySpace>(
            layout, is_preconditioner, n_vars );
    else
        throw std::runtime_error(
            "Cabana::Grid::createHypreSemiStructuredSolver: Invalid solver "
            "type" );
}
 
//---------------------------------------------------------------------------//
 
} // namespace Grid
} // namespace Cabana
 
#endif // end CABANA_GRID_HypreSemiStRUCTUREDSOLVER_HPP