general_purpose_block_preconditioners.cc

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// LIC// ====================================================================
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// LIC// at http://www.oomph-lib.org.
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// LIC// Copyright (C) 2006-2024 Matthias Heil and Andrew Hazel
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#include "oomph_definitions.h"
#include "preconditioner.h"
#include "block_preconditioner.h"
#include "matrices.h"
#include "general_purpose_block_preconditioners.h"
 
namespace oomph
{
  //============================================================================
  /// setup for the block diagonal preconditioner
  //============================================================================
  template<typename MATRIX>
  void BlockDiagonalPreconditioner<MATRIX>::setup()
  {
    // clean the memory
    this->clean_up_memory();
 
    // Note: Subsidiary block preconditioners don't really use their
    // mesh pointers (since the lookup schemes inferred from them are
    // set up by their masters). Generally we insist that (for uniformity)
    // a mesh should be set, but sometimes subsidiary preconditioners are
    // set up on the fly and we can't sensibly set meshes, so we're
    // forgiving...)
    if (this->is_master_block_preconditioner())
    {
#ifdef PARANOID
      if (this->gp_nmesh() == 0)
      {
        std::ostringstream err_msg;
        err_msg << "There are no meshes set.\n"
                << "Did you remember to call add_mesh(...)?";
        throw OomphLibError(
          err_msg.str(), OOMPH_CURRENT_FUNCTION, OOMPH_EXCEPTION_LOCATION);
      }
#endif
 
      // Set all meshes if this is master block preconditioner
      this->gp_preconditioner_set_all_meshes();
    }
 
    // If we're meant to build silently
    if (this->Silent_preconditioner_setup == true)
    {
      // Store the output stream pointer
      this->Stream_pt = oomph_info.stream_pt();
 
      // Now set the oomph_info stream pointer to the null stream to
      // disable all possible output
      oomph_info.stream_pt() = &oomph_nullstream;
    }
 
    // Set up the block look up schemes
    this->gp_preconditioner_block_setup();
 
    // number of types of blocks.
    unsigned nblock_types = this->nblock_types();
 
    // Create any subsidiary preconditioners needed
    this->fill_in_subsidiary_preconditioners(nblock_types);
 
    // The total time for extracting all the blocks from the "global" matrix
    double t_extraction_total = 0.0;
 
    // The total time for setting up the subsidiary preconditioners
    double t_subsidiary_setup_total = 0.0;
 
    // If using two level parallelisation then we need to use a
    // PrecondtionerArray which requires very different setup. ??ds possibly
    // it should have it's own class?
    if (Use_two_level_parallelisation)
    {
      // Get the blocks. We have to use new because you can't have containers
      // of matrices because the copy constructor is buggy (so we create a
      // container of pointers instead). ??ds
      Vector<CRDoubleMatrix*> block_diagonal_matrix_pt(nblock_types, 0);
      for (unsigned i = 0; i < nblock_types; i++)
      {
        // Allocate space for the new matrix
        block_diagonal_matrix_pt[i] = new CRDoubleMatrix;
 
        // Get the start time
        double t_extract_start = TimingHelpers::timer();
 
        // Extract the i-th block
        this->get_block(
          i, get_other_diag_ds(i, nblock_types), *block_diagonal_matrix_pt[i]);
 
        // Get the end time
        double t_extract_end = TimingHelpers::timer();
 
        // Update the timing total
        t_extraction_total += (t_extract_end - t_extract_start);
      }
 
      // Construct the preconditioner array
      Preconditioner_array_pt = new PreconditionerArray;
 
      // Get the start time
      double t_subsidiary_setup_start = TimingHelpers::timer();
 
      // Set up the preconditioners
      Preconditioner_array_pt->setup_preconditioners(
        block_diagonal_matrix_pt,
        this->Subsidiary_preconditioner_pt,
        this->comm_pt());
 
      // Get the end time
      double t_subsidiary_setup_end = TimingHelpers::timer();
 
      // Update the timing total
      t_subsidiary_setup_total +=
        (t_subsidiary_setup_end - t_subsidiary_setup_start);
 
      // and delete the blocks
      for (unsigned i = 0; i < nblock_types; i++)
      {
        delete block_diagonal_matrix_pt[i];
        block_diagonal_matrix_pt[i] = 0;
      }
 
      // Preconditioner array is weird, it calls delete on all the
      // preconditioners you give it and requires new ones each time!
      this->Subsidiary_preconditioner_pt.clear();
    }
    // Otherwise just set up each block's preconditioner in order
    else
    {
      for (unsigned i = 0; i < nblock_types; i++)
      {
        // Get the block
        unsigned j = get_other_diag_ds(i, nblock_types);
 
        // Get the start time
        double t_extract_start = TimingHelpers::timer();
 
        // Get the block
        CRDoubleMatrix block = this->get_block(i, j);
 
        // Get the end time
        double t_extract_end = TimingHelpers::timer();
 
        // Update the timing total
        t_extraction_total += (t_extract_end - t_extract_start);
 
        // Get the start time
        double t_subsidiary_setup_start = TimingHelpers::timer();
 
        // Set the (subsidiary) preconditioner up for this block
        this->Subsidiary_preconditioner_pt[i]->setup(&block);
 
        // Get the end time
        double t_subsidiary_setup_end = TimingHelpers::timer();
 
        // Tell the user
        oomph_info << "Took "
                   << t_subsidiary_setup_end - t_subsidiary_setup_start
                   << "s to setup." << std::endl;
 
        // Update the timing total
        t_subsidiary_setup_total +=
          (t_subsidiary_setup_end - t_subsidiary_setup_start);
      }
    }
 
    // If we're meant to build silently, reassign the oomph stream pointer
    if (this->Silent_preconditioner_setup == true)
    {
      // Store the output stream pointer
      oomph_info.stream_pt() = this->Stream_pt;
 
      // Reset our own stream pointer
      this->Stream_pt = 0;
    }
 
    // Tell the user
    oomph_info << "Total block extraction time [sec]: " << t_extraction_total
               << "\nTotal subsidiary preconditioner setup time [sec]: "
               << t_subsidiary_setup_total << std::endl;
  }
 
  //=============================================================================
  /// Preconditioner solve for the block diagonal preconditioner
  //=============================================================================
  template<typename MATRIX>
  void BlockDiagonalPreconditioner<MATRIX>::preconditioner_solve(
    const DoubleVector& r, DoubleVector& z)
  {
    // Cache umber of block types
    unsigned n_block = this->nblock_types();
 
    // Get the right hand side vector (b in Ax = b) in block form.
    Vector<DoubleVector> block_r;
    this->get_block_vectors(r, block_r);
 
    // Make sure z vector is built
    if (!z.built())
    {
      z.build(this->distribution_pt(), 0.0);
    }
 
    // Vector of vectors for storage of solution in block form.
    Vector<DoubleVector> block_z(n_block);
 
    if (Use_two_level_parallelisation)
    {
      Preconditioner_array_pt->solve_preconditioners(block_r, block_z);
    }
    else
    {
      // solve each diagonal block
      for (unsigned i = 0; i < n_block; i++)
      {
        double t_start = 0.0;
        if (Doc_time_during_preconditioner_solve)
        {
          t_start = TimingHelpers::timer();
        }
 
        // this->Subsidiary_preconditioner_pt[i]->preconditioner_solve(block_r[i],
        //     block_z[i]);
 
 
        // See if the i-th subsidiary preconditioner is a block preconditioner
        if (dynamic_cast<BlockPreconditioner<CRDoubleMatrix>*>(
              this->Subsidiary_preconditioner_pt[i]) == 0)
        {
          this->Subsidiary_preconditioner_pt[i]->preconditioner_solve(
            block_r[i], block_z[i]);
        }
        // If the subsidiary preconditioner is a block preconditioner
        else
        {
          // This is pretty inefficient but there is no other way to do this
          // with block sub preconditioners as far as I can tell because they
          // demand to have the full r and z vectors...
          DoubleVector block_z_with_size_of_full_z(r.distribution_pt());
          DoubleVector r_updated(r.distribution_pt());
 
          // Construct the new r vector (with the update given by back subs
          // below).
          this->return_block_vectors(block_r, r_updated);
 
          // Solve (blocking is handled inside the block preconditioner).
          this->Subsidiary_preconditioner_pt[i]->preconditioner_solve(
            r_updated, block_z_with_size_of_full_z);
 
          // Extract this block's z vector because we need it for the next step
          // (and throw away block_z_with_size_of_full_z).
          this->get_block_vector(i, block_z_with_size_of_full_z, block_z[i]);
        }
 
 
        if (Doc_time_during_preconditioner_solve)
        {
          oomph_info << "Time for application of " << i
                     << "-th block preconditioner: "
                     << TimingHelpers::timer() - t_start << std::endl;
        }
      }
    }
 
    // copy solution in block vectors block_z back to z
    this->return_block_vectors(block_z, z);
  }
 
 
  //============================================================================
  /// setup for the block triangular preconditioner
  //============================================================================
  template<typename MATRIX>
  void BlockTriangularPreconditioner<MATRIX>::setup()
  {
    // clean the memory
    this->clean_up_memory();
 
    // Subsidiary preconditioners don't really need the meshes
    if (this->is_master_block_preconditioner())
    {
#ifdef PARANOID
      if (this->gp_nmesh() == 0)
      {
        std::ostringstream err_msg;
        err_msg << "There are no meshes set.\n"
                << "Did you remember to call add_mesh(...)?";
        throw OomphLibError(
          err_msg.str(), OOMPH_CURRENT_FUNCTION, OOMPH_EXCEPTION_LOCATION);
      }
#endif
 
      // Set all meshes if this is master block preconditioner
      this->gp_preconditioner_set_all_meshes();
    }
 
    // If we're meant to build silently
    if (this->Silent_preconditioner_setup == true)
    {
      // Store the output stream pointer
      this->Stream_pt = oomph_info.stream_pt();
 
      // Now set the oomph_info stream pointer to the null stream to
      // disable all possible output
      oomph_info.stream_pt() = &oomph_nullstream;
    }
 
    // Set up the block look up schemes
    this->gp_preconditioner_block_setup();
 
    // number of block types
    unsigned nblock_types = this->nblock_types();
 
    // storage for the off diagonal matrix vector products
    Off_diagonal_matrix_vector_products.resize(nblock_types, nblock_types, 0);
 
    // Fill in any null subsidiary preconditioners
    this->fill_in_subsidiary_preconditioners(nblock_types);
 
    // The total time for extracting all the blocks from the "global" matrix
    double t_extraction_total = 0.0;
 
    // The total time for setting up the subsidiary preconditioners
    double t_subsidiary_setup_total = 0.0;
 
    // The total time for setting up the matrix-vector products
    double t_mvp_setup_total = 0.0;
 
    // build the preconditioners and matrix vector products
    for (unsigned i = 0; i < nblock_types; i++)
    {
      // Get the block and set up the preconditioner.
      {
        // Get the start time
        double t_extract_start = TimingHelpers::timer();
 
        // Grab the i-th diagonal block
        CRDoubleMatrix block_matrix = this->get_block(i, i);
 
        // Get the end time
        double t_extract_end = TimingHelpers::timer();
 
        // Update the timing total
        t_extraction_total += (t_extract_end - t_extract_start);
 
        // Get the start time
        double t_subsidiary_setup_start = TimingHelpers::timer();
 
        // Set up the i-th subsidiary preconditioner with this block
        this->Subsidiary_preconditioner_pt[i]->setup(&block_matrix);
 
        // Get the end time
        double t_subsidiary_setup_end = TimingHelpers::timer();
 
        // Update the timing total
        t_subsidiary_setup_total +=
          (t_subsidiary_setup_end - t_subsidiary_setup_start);
      }
 
      // next setup the off diagonal mat vec operators
      unsigned l, u;
      if (Upper_triangular)
      {
        l = i + 1;
        u = nblock_types;
      }
      else
      {
        l = 0;
        u = i;
      }
 
      for (unsigned j = l; j < u; j++)
      {
        // Get the start time
        double t_extract_start = TimingHelpers::timer();
 
        // Get the block
        CRDoubleMatrix block_matrix = this->get_block(i, j);
 
        // Get the end time
        double t_extract_end = TimingHelpers::timer();
 
        // Update the timing total
        t_extraction_total += (t_extract_end - t_extract_start);
 
        // Get the start time
        double t_mvp_start = TimingHelpers::timer();
 
        // Copy the block into a "multiplier" class. If trilinos is being
        // used this should also be faster than oomph-lib's multiphys.
        Off_diagonal_matrix_vector_products(i, j) = new MatrixVectorProduct();
 
        // Set the damn thing up
        this->setup_matrix_vector_product(
          Off_diagonal_matrix_vector_products(i, j), &block_matrix, j);
 
        // Get the end time
        double t_mvp_end = TimingHelpers::timer();
 
        // Update the timing total
        t_mvp_setup_total += (t_mvp_end - t_mvp_start);
      }
    }
 
    // Tell the user
    oomph_info << "Total block extraction time [sec]: " << t_extraction_total
               << "\nTotal subsidiary preconditioner setup time [sec]: "
               << t_subsidiary_setup_total
               << "\nTotal matrix-vector product setup time [sec]: "
               << t_mvp_setup_total << std::endl;
 
    // If we're meant to build silently, reassign the oomph stream pointer
    if (this->Silent_preconditioner_setup == true)
    {
      // Store the output stream pointer
      oomph_info.stream_pt() = this->Stream_pt;
 
      // Reset our own stream pointer
      this->Stream_pt = 0;
    }
  } // End of setup
 
  //=============================================================================
  /// Preconditioner solve for the block triangular preconditioner
  //=============================================================================
  template<typename MATRIX>
  void BlockTriangularPreconditioner<MATRIX>::preconditioner_solve(
    const DoubleVector& r, DoubleVector& z)
  {
    // Cache number of block types
    unsigned n_block = this->nblock_types();
 
    //
    int start, end, step;
    if (Upper_triangular)
    {
      start = n_block - 1;
      end = -1;
      step = -1;
    }
    else
    {
      start = 0;
      end = n_block;
      step = 1;
    }
 
    // vector of vectors for each section of residual vector
    Vector<DoubleVector> block_r;
 
    // rearrange the vector r into the vector of block vectors block_r
    this->get_block_vectors(r, block_r);
 
    // vector of vectors for the solution block vectors
    Vector<DoubleVector> block_z(n_block);
 
    //
    for (int i = start; i != end; i += step)
    {
      // ??ds ugly, fix this?
      if (dynamic_cast<BlockPreconditioner<CRDoubleMatrix>*>(
            this->Subsidiary_preconditioner_pt[i]) == 0)
      {
        // solve on the block
        this->Subsidiary_preconditioner_pt[i]->preconditioner_solve(block_r[i],
                                                                    block_z[i]);
      }
      else
      {
        // This is pretty inefficient but there is no other way to do this with
        // block sub preconditioners as far as I can tell because they demand
        // to have the full r and z vectors...
 
        DoubleVector block_z_with_size_of_full_z(r.distribution_pt()),
          r_updated(r.distribution_pt());
 
        // Construct the new r vector (with the update given by back subs
        // below).
        this->return_block_vectors(block_r, r_updated);
 
        // Solve (blocking is handled inside the block preconditioner).
        this->Subsidiary_preconditioner_pt[i]->preconditioner_solve(
          r_updated, block_z_with_size_of_full_z);
 
        // Extract this block's z vector because we need it for the next step
        // (and throw away block_z_with_size_of_full_z).
        this->get_block_vector(i, block_z_with_size_of_full_z, block_z[i]);
      }
 
      // substitute
      for (int j = i + step; j != end; j += step)
      {
        DoubleVector temp;
        Off_diagonal_matrix_vector_products(j, i)->multiply(block_z[i], temp);
        block_r[j] -= temp;
      }
    }
 
    // copy solution in block vectors block_r back to z
    this->return_block_vectors(block_z, z);
  }
 
 
  //=============================================================================
  /// Setup for the exact block preconditioner
  //=============================================================================
  template<typename MATRIX>
  void ExactBlockPreconditioner<MATRIX>::setup()
  {
    // If this is a master block preconditioner,
    // we give the mesh pointers to the BlockPreconditioner base class.
    // Subsidiary preconditioners don't need meshes...
    if (this->is_master_block_preconditioner())
    {
#ifdef PARANOID
      if (this->gp_nmesh() == 0)
      {
        std::ostringstream err_msg;
        err_msg << "There are no meshes set.\n"
                << "Did you remember to call add_mesh(...)?";
        throw OomphLibError(
          err_msg.str(), OOMPH_CURRENT_FUNCTION, OOMPH_EXCEPTION_LOCATION);
      }
#endif
 
      // Set all meshes if this is master block preconditioner
      this->gp_preconditioner_set_all_meshes();
    }
 
    // Set up the block look up schemes
    this->gp_preconditioner_block_setup();
 
    // get the number of DOF types
    unsigned nblock_types = this->nblock_types();
 
    // Build the preconditioner matrix
    VectorMatrix<BlockSelector> required_blocks(nblock_types, nblock_types);
 
    // boolean indicating if we want the block, stored for readability.
    const bool want_block = true;
    for (unsigned b_i = 0; b_i < nblock_types; b_i++)
    {
      for (unsigned b_j = 0; b_j < nblock_types; b_j++)
      {
        required_blocks[b_i][b_j].select_block(b_i, b_j, want_block);
      }
    }
 
    // Get the concatenated blocks
    CRDoubleMatrix exact_block_matrix =
      this->get_concatenated_block(required_blocks);
 
    // Setup the preconditioner.
    this->fill_in_subsidiary_preconditioners(1); // Only need one preconditioner
    preconditioner_pt()->setup(&exact_block_matrix);
  }
 
  //=============================================================================
  /// Preconditioner solve for the exact block preconditioner
  //=============================================================================
  template<typename MATRIX>
  void ExactBlockPreconditioner<MATRIX>::preconditioner_solve(
    const DoubleVector& r, DoubleVector& z)
  {
    // get  the block ordered components of the r vector for this preconditioner
    DoubleVector block_order_r;
    this->get_block_ordered_preconditioner_vector(r, block_order_r);
 
    // vector for solution
    DoubleVector block_order_z;
 
    // apply the preconditioner
    preconditioner_pt()->preconditioner_solve(block_order_r, block_order_z);
 
    // copy solution back to z vector
    this->return_block_ordered_preconditioner_vector(block_order_z, z);
  }
 
  template class BlockDiagonalPreconditioner<CRDoubleMatrix>;
  template class BlockTriangularPreconditioner<CRDoubleMatrix>;
  template class ExactBlockPreconditioner<CRDoubleMatrix>;
  template class BlockAntiDiagonalPreconditioner<CRDoubleMatrix>;
  template class DummyBlockPreconditioner<CRDoubleMatrix>;
 
} // namespace oomph