PCBlockDiagonal.cpp

/*

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*/

#include <iostream>

#include "PetscVecTools.hpp" // Includes Ublas so must come first
#include "PCBlockDiagonal.hpp"
#include "Exception.hpp"
#include "Warnings.hpp"

#ifdef TRACE_KSP
#include "Timer.hpp"
#endif

PCBlockDiagonal::PCBlockDiagonal(KSP& rKspObject)
{
#ifdef TRACE_KSP
    mPCContext.mScatterTime = 0.0;
    mPCContext.mA1PreconditionerTime = 0.0;
    mPCContext.mA2PreconditionerTime = 0.0;
    mPCContext.mGatherTime = 0.0;;
#endif

    PCBlockDiagonalCreate(rKspObject);
    PCBlockDiagonalSetUp();
}

PCBlockDiagonal::~PCBlockDiagonal()
{
#ifdef TRACE_KSP
    if (PetscTools::AmMaster())
    {
        std::cout << " -- Block diagonal preconditioner profile information: " << std::endl;
        std::cout << "\t mScatterTime: " << mPCContext.mScatterTime << std::endl;
        std::cout << "\t mA1PreconditionerTime: " << mPCContext.mA1PreconditionerTime << std::endl;
        std::cout << "\t mA2PreconditionerTime: " << mPCContext.mA2PreconditionerTime << std::endl;
        std::cout << "\t mGatherTime: " << mPCContext.mGatherTime << std::endl;
    }
#endif

    PetscTools::Destroy(mPCContext.A11_matrix_subblock);
    PetscTools::Destroy(mPCContext.A22_matrix_subblock);

    PCDestroy(PETSC_DESTROY_PARAM(mPCContext.PC_amg_A11));
    PCDestroy(PETSC_DESTROY_PARAM(mPCContext.PC_amg_A22));

    PetscTools::Destroy(mPCContext.x1_subvector);
    PetscTools::Destroy(mPCContext.y1_subvector);

    PetscTools::Destroy(mPCContext.x2_subvector);
    PetscTools::Destroy(mPCContext.y2_subvector);

    VecScatterDestroy(PETSC_DESTROY_PARAM(mPCContext.A11_scatter_ctx));
    VecScatterDestroy(PETSC_DESTROY_PARAM(mPCContext.A22_scatter_ctx));
}

void PCBlockDiagonal::PCBlockDiagonalCreate(KSP& rKspObject)
{
    KSPGetPC(rKspObject, &mPetscPCObject);

    Mat system_matrix, dummy;
#if (PETSC_VERSION_MAJOR==3 && PETSC_VERSION_MINOR>=5)
    KSPGetOperators(rKspObject, &system_matrix, &dummy);
#else
    MatStructure flag;
    KSPGetOperators(rKspObject, &system_matrix, &dummy, &flag);
#endif

    PetscInt num_rows, num_columns;
    MatGetSize(system_matrix, &num_rows, &num_columns);
    assert(num_rows==num_columns);

    PetscInt num_local_rows, num_local_columns;
    MatGetLocalSize(system_matrix, &num_local_rows, &num_local_columns);

    // Odd number of rows: impossible in Bidomain.
    // Odd number of local rows: impossible if V_m and phi_e for each node are stored in the same processor.
    if ((num_rows%2 != 0) || (num_local_rows%2 != 0))
    {
        TERMINATE("Wrong matrix parallel layout detected in PCBlockDiagonal."); // LCOV_EXCL_LINE
    }

    // Allocate memory
    unsigned subvector_num_rows = num_rows/2;
    unsigned subvector_local_rows = num_local_rows/2;
    mPCContext.x1_subvector = PetscTools::CreateVec(subvector_num_rows, subvector_local_rows);
    mPCContext.x2_subvector = PetscTools::CreateVec(subvector_num_rows, subvector_local_rows);
    mPCContext.y1_subvector = PetscTools::CreateVec(subvector_num_rows, subvector_local_rows);
    mPCContext.y2_subvector = PetscTools::CreateVec(subvector_num_rows, subvector_local_rows);

    // Create scatter contexts
    {
        // Needed by SetupInterleavedVectorScatterGather in order to find out parallel layout.
        Vec dummy_vec = PetscTools::CreateVec(num_rows, num_local_rows);

        PetscVecTools::SetupInterleavedVectorScatterGather(dummy_vec, mPCContext.A11_scatter_ctx, mPCContext.A22_scatter_ctx);

        PetscTools::Destroy(dummy_vec);
    }

    // Get matrix sublock A11
    {
        // Work out local row range for subblock A11 (same as x1 or y1)
        PetscInt low, high, global_size;
        VecGetOwnershipRange(mPCContext.x1_subvector, &low, &high);
        VecGetSize(mPCContext.x1_subvector, &global_size);
        assert(global_size == num_rows/2);

        IS A11_local_rows;
        IS A11_columns;
        ISCreateStride(PETSC_COMM_WORLD, high-low, 2*low, 2, &A11_local_rows);
        ISCreateStride(PETSC_COMM_WORLD, global_size, 0, 2, &A11_columns);

#if (PETSC_VERSION_MAJOR == 3 && PETSC_VERSION_MINOR >= 1) //PETSc 3.1 or later
        MatGetSubMatrix(system_matrix, A11_local_rows, A11_local_rows,
            MAT_INITIAL_MATRIX, &mPCContext.A11_matrix_subblock);
#else
        MatGetSubMatrix(system_matrix, A11_local_rows, A11_columns, PETSC_DECIDE,
            MAT_INITIAL_MATRIX, &mPCContext.A11_matrix_subblock);
#endif


        ISDestroy(PETSC_DESTROY_PARAM(A11_local_rows));
        ISDestroy(PETSC_DESTROY_PARAM(A11_columns));
    }

    // Get matrix sublock A22
    {
        // Work out local row range for subblock A22 (same as x2 or y2)
        PetscInt low, high, global_size;
        VecGetOwnershipRange(mPCContext.x2_subvector, &low, &high);
        VecGetSize(mPCContext.x2_subvector, &global_size);
        assert(global_size == num_rows/2);

        IS A22_local_rows;
        IS A22_columns;
        ISCreateStride(PETSC_COMM_WORLD, high-low, 2*low+1, 2, &A22_local_rows);
        ISCreateStride(PETSC_COMM_WORLD, global_size, 1, 2, &A22_columns);

#if (PETSC_VERSION_MAJOR == 3 && PETSC_VERSION_MINOR >= 1) //PETSc 3.1 or later
        MatGetSubMatrix(system_matrix, A22_local_rows, A22_local_rows,
            MAT_INITIAL_MATRIX, &mPCContext.A22_matrix_subblock);
#else
        MatGetSubMatrix(system_matrix, A22_local_rows, A22_columns, PETSC_DECIDE,
            MAT_INITIAL_MATRIX, &mPCContext.A22_matrix_subblock);
#endif

        ISDestroy(PETSC_DESTROY_PARAM(A22_local_rows));
        ISDestroy(PETSC_DESTROY_PARAM(A22_columns));
    }

    // Register call-back function and its context
    PCSetType(mPetscPCObject, PCSHELL);
#if (PETSC_VERSION_MAJOR == 2 && PETSC_VERSION_MINOR == 2) //PETSc 2.2
    PCShellSetApply(mPetscPCObject, PCBlockDiagonalApply, (void*) &mPCContext);
#else
    // Register PC context so it gets passed to PCBlockDiagonalApply
    PCShellSetContext(mPetscPCObject, &mPCContext);

    // Register call-back function
    PCShellSetApply(mPetscPCObject, PCBlockDiagonalApply);
#endif

}

void PCBlockDiagonal::PCBlockDiagonalSetUp()
{
    // These options will get read by PCSetFromOptions
//     PetscTools::SetOption("-pc_hypre_boomeramg_max_iter", "1");
//     PetscTools::SetOption("-pc_hypre_boomeramg_strong_threshold", "0.0");
//     PetscTools::SetOption("-pc_hypre_type", "boomeramg");

    // Set up amg preconditioner for block A11
    PCCreate(PETSC_COMM_WORLD, &(mPCContext.PC_amg_A11));

    //    PCSetType(mPCContext.PC_amg_A11, PCBJACOBI);

    // We are expecting an error from PETSC on systems that don't have the hypre library, so suppress it
    // in case it aborts
    PetscPushErrorHandler(PetscIgnoreErrorHandler, nullptr);
    PetscErrorCode pc_set_error = PCSetType(mPCContext.PC_amg_A11, PCHYPRE);
    if (pc_set_error != 0)
    {
        WARNING("PETSc hypre preconditioning library is not installed");
    }
    // Stop supressing error
    PetscPopErrorHandler();

#if (PETSC_VERSION_MAJOR==3 && PETSC_VERSION_MINOR<=5)
    PetscTools::SetOption("-pc_hypre_type", "euclid");
    PetscTools::SetOption("-pc_hypre_euclid_levels", "0");
#else
/* euclid was removed in 3.6. Use the previously-commented-out alternative */
    PetscTools::SetOption("-pc_hypre_type", "boomeramg");
    PetscTools::SetOption("-pc_hypre_boomeramg_max_iter", "1");
    PetscTools::SetOption("-pc_hypre_boomeramg_strong_threshold", "0.0");
    PetscTools::SetOption("-pc_hypre_boomeramg_coarsen_type", "HMIS");
#endif

#if (PETSC_VERSION_MAJOR==3 && PETSC_VERSION_MINOR>=5)
    // Attempt to emulate SAME_PRECONDITIONER below
    PCSetReusePreconditioner(mPCContext.PC_amg_A11, PETSC_TRUE);
    PCSetOperators(mPCContext.PC_amg_A11, mPCContext.A11_matrix_subblock, mPCContext.A11_matrix_subblock);
#else
    PCSetOperators(mPCContext.PC_amg_A11, mPCContext.A11_matrix_subblock, mPCContext.A11_matrix_subblock, SAME_PRECONDITIONER);
#endif
    PCSetFromOptions(mPCContext.PC_amg_A11);
    PCSetUp(mPCContext.PC_amg_A11);

    // Set up amg preconditioner for block A22
    PCCreate(PETSC_COMM_WORLD, &(mPCContext.PC_amg_A22));

    /* Full AMG in the block */
    PetscPushErrorHandler(PetscIgnoreErrorHandler, nullptr);
    PCSetType(mPCContext.PC_amg_A22, PCHYPRE);
    // Stop supressing error
    PetscPopErrorHandler();

    //PCHYPRESetType(mPCContext.PC_amg_A22, "boomeramg");
    PetscTools::SetOption("-pc_hypre_type", "boomeramg");
    PetscTools::SetOption("-pc_hypre_boomeramg_max_iter", "1");
    PetscTools::SetOption("-pc_hypre_boomeramg_strong_threshold", "0.0");
    PetscTools::SetOption("-pc_hypre_boomeramg_coarsen_type", "HMIS");
    //PetscTools::SetOption("-pc_hypre_boomeramg_relax_type_all","Jacobi");
    //PetscTools::SetOption("-pc_hypre_boomeramg_max_levels","10");
    //PetscTools::SetOption("-pc_hypre_boomeramg_agg_nl", "1");
    //PetscTools::SetOption("-pc_hypre_boomeramg_print_statistics","");
    //PetscTools::SetOption("-pc_hypre_boomeramg_interp_type","standard");
    //PetscTools::SetOption("-pc_hypre_boomeramg_interp_type","ext+i");

    //    PCHYPRESetType(mPCContext.PC_amg_A22, "euclid");

    /* Block Jacobi with AMG at each block */
    //     PCSetType(mPCContext.PC_amg_A22, PCBJACOBI);

    //     PetscTools::SetOption("-sub_pc_type", "hypre");

    //     PetscTools::SetOption("-sub_pc_hypre_type", "boomeramg");
    //     PetscTools::SetOption("-sub_pc_hypre_boomeramg_max_iter", "1");
    //     PetscTools::SetOption("-sub_pc_hypre_boomeramg_strong_threshold", "0.0");

    //     PetscTools::SetOption("-pc_hypre_type", "boomeramg");
    //     PetscTools::SetOption("-pc_hypre_boomeramg_max_iter", "1");
    //     PetscTools::SetOption("-pc_hypre_boomeramg_strong_threshold", "0.0");

    /* Additive Schwarz with AMG at each block */
//     PCSetType(mPCContext.PC_amg_A22, PCASM);

//     PetscTools::SetOption("-pc_asm_type", "basic");
//     PetscTools::SetOption("-pc_asm_overlap", "1");

//     PetscTools::SetOption("-sub_ksp_type", "preonly");

//     PetscTools::SetOption("-sub_pc_type", "hypre");

//     PetscTools::SetOption("-sub_pc_hypre_type", "boomeramg");
//     PetscTools::SetOption("-sub_pc_hypre_boomeramg_max_iter", "1");
//     PetscTools::SetOption("-sub_pc_hypre_boomeramg_strong_threshold", "0.0");

#if (PETSC_VERSION_MAJOR==3 && PETSC_VERSION_MINOR>=5)
    // Attempt to emulate SAME_PRECONDITIONER below
    PCSetReusePreconditioner(mPCContext.PC_amg_A22, PETSC_TRUE);
    PCSetOperators(mPCContext.PC_amg_A22, mPCContext.A22_matrix_subblock, mPCContext.A22_matrix_subblock);
#else
    PCSetOperators(mPCContext.PC_amg_A22, mPCContext.A22_matrix_subblock, mPCContext.A22_matrix_subblock, SAME_PRECONDITIONER);
#endif
    PCSetFromOptions(mPCContext.PC_amg_A22);
    PCSetUp(mPCContext.PC_amg_A22);
}

#if (PETSC_VERSION_MAJOR == 3 && PETSC_VERSION_MINOR >= 1) //PETSc 3.1 or later
PetscErrorCode PCBlockDiagonalApply(PC pc_object, Vec x, Vec y)
{
  void* pc_context;

  PCShellGetContext(pc_object, &pc_context);
#else
PetscErrorCode PCBlockDiagonalApply(void* pc_context, Vec x, Vec y)
{
#endif

    // Cast the context pointer to PCBlockDiagonalContext
    PCBlockDiagonal::PCBlockDiagonalContext* block_diag_context = (PCBlockDiagonal::PCBlockDiagonalContext*) pc_context;
    assert(block_diag_context!=nullptr);

    /*
     * Scatter x = [x1 x2]'
     */
#ifdef TRACE_KSP
    Timer::Reset();
#endif

    PetscVecTools::DoInterleavedVecScatter(x, block_diag_context->A11_scatter_ctx, block_diag_context->x1_subvector, block_diag_context->A22_scatter_ctx, block_diag_context->x2_subvector);

#ifdef TRACE_KSP
    block_diag_context->mScatterTime += Timer::GetElapsedTime();
#endif

    /*
     * y1 = AMG(A11)*x1
     * y2 = AMG(A22)*x2
     */
#ifdef TRACE_KSP
    Timer::Reset();
#endif
    PCApply(block_diag_context->PC_amg_A11, block_diag_context->x1_subvector, block_diag_context->y1_subvector);
#ifdef TRACE_KSP
    block_diag_context->mA1PreconditionerTime += Timer::GetElapsedTime();
#endif

#ifdef TRACE_KSP
    Timer::Reset();
#endif
    PCApply(block_diag_context->PC_amg_A22, block_diag_context->x2_subvector, block_diag_context->y2_subvector);
#ifdef TRACE_KSP
    block_diag_context->mA2PreconditionerTime += Timer::GetElapsedTime();
#endif

    /*
     * Gather y = [y1 y2]'
     */
//PETSc-3.x.x or PETSc-2.3.3
#ifdef TRACE_KSP
    Timer::Reset();
#endif

    PetscVecTools::DoInterleavedVecGather(y, block_diag_context->A11_scatter_ctx, block_diag_context->y1_subvector, block_diag_context->A22_scatter_ctx, block_diag_context->y2_subvector);

#ifdef TRACE_KSP
    block_diag_context->mGatherTime += Timer::GetElapsedTime();
#endif
    return 0;
}