StitchedMeshGenerator.C

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//* This file is part of the MOOSE framework
//* https://mooseframework.inl.gov
//*
//* All rights reserved, see COPYRIGHT for full restrictions
//* https://github.com/idaholab/moose/blob/master/COPYRIGHT
//*
//* Licensed under LGPL 2.1, please see LICENSE for details
//* https://www.gnu.org/licenses/lgpl-2.1.html

#include "StitchedMeshGenerator.h"

#include "CastUniquePointer.h"
#include "MooseUtils.h"
#include "MooseMeshUtils.h"

#include "libmesh/unstructured_mesh.h"

registerMooseObject("MooseApp", StitchedMeshGenerator);

InputParameters
StitchedMeshGenerator::validParams()
{
  InputParameters params = MeshGenerator::validParams();

  MooseEnum algorithm("BINARY EXHAUSTIVE", "BINARY");

  params.addRequiredParam<std::vector<MeshGeneratorName>>("inputs", "The input MeshGenerators.");
  params.addParam<bool>(
      "clear_stitched_boundary_ids", true, "Whether or not to clear the stitched boundary IDs");
  params.addRequiredParam<std::vector<std::vector<std::string>>>(
      "stitch_boundaries_pairs",
      "Pairs of boundaries to be stitched together between the 1st mesh in inputs and each "
      "consecutive mesh");
  params.addParam<MooseEnum>(
      "algorithm",
      algorithm,
      "Control the use of binary search for the nodes of the stitched surfaces.");
  params.addParam<bool>("prevent_boundary_ids_overlap",
                        true,
                        "Whether to re-number boundaries in stitched meshes to prevent merging of "
                        "unrelated boundaries");
  params.addParam<bool>(
      "merge_boundaries_with_same_name",
      true,
      "If the input meshes have boundaries with the same name (but different IDs), merge them");
  params.addParam<bool>(
      "verbose_stitching", false, "Whether mesh stitching should have verbose output.");
  params.addClassDescription(
      "Allows multiple mesh files to be stitched together to form a single mesh.");

  return params;
}

StitchedMeshGenerator::StitchedMeshGenerator(const InputParameters & parameters)
  : MeshGenerator(parameters),
    _mesh_ptrs(getMeshes("inputs")),
    _input_names(getParam<std::vector<MeshGeneratorName>>("inputs")),
    _clear_stitched_boundary_ids(getParam<bool>("clear_stitched_boundary_ids")),
    _stitch_boundaries_pairs(
        getParam<std::vector<std::vector<std::string>>>("stitch_boundaries_pairs")),
    _algorithm(parameters.get<MooseEnum>("algorithm")),
    _prevent_boundary_ids_overlap(getParam<bool>("prevent_boundary_ids_overlap")),
    _merge_boundaries_with_same_name(getParam<bool>("merge_boundaries_with_same_name"))
{
}

std::unique_ptr<MeshBase>
StitchedMeshGenerator::generate()
{
  // We put the first mesh in a local pointer
  std::unique_ptr<UnstructuredMesh> mesh = dynamic_pointer_cast<UnstructuredMesh>(*_mesh_ptrs[0]);
  if (!mesh) // This should never happen until libMesh implements on-the-fly-Elem mesh types
    mooseError("StitchedMeshGenerator is only implemented for unstructured meshes");

  // Reserve spaces for the other meshes (no need to store the first one another time)
  std::vector<std::unique_ptr<UnstructuredMesh>> meshes(_mesh_ptrs.size() - 1);

  // Read in all of the other meshes
  for (MooseIndex(_mesh_ptrs) i = 1; i < _mesh_ptrs.size(); ++i)
    meshes[i - 1] = dynamic_pointer_cast<UnstructuredMesh>(*_mesh_ptrs[i]);

  // Stitch all the meshes to the first one
  for (MooseIndex(meshes) i = 0; i < meshes.size(); i++)
  {
    auto boundary_pair = _stitch_boundaries_pairs[i];

    boundary_id_type first, second;

    try
    {
      first = MooseUtils::convert<boundary_id_type>(boundary_pair[0], true);
    }
    catch (...)
    {
      first = mesh->get_boundary_info().get_id_by_name(boundary_pair[0]);

      if (first == BoundaryInfo::invalid_id)
      {
        std::stringstream error;

        error << "Boundary " << boundary_pair[0] << " doesn't exist on mesh '" << _input_names[0]
              << "' in generator " << name() << "\n";
        error << "Boundary (sideset) names that do exist: \n";
        error << " ID : Name\n";

        auto & sideset_id_name_map = mesh->get_boundary_info().get_sideset_name_map();

        for (auto & ss_name_map_pair : sideset_id_name_map)
          error << " " << ss_name_map_pair.first << " : " << ss_name_map_pair.second << "\n";

        error << "\nBoundary (nodeset) names that do exist: \n";
        error << " ID : Name\n";

        auto & nodeset_id_name_map = mesh->get_boundary_info().get_nodeset_name_map();

        for (auto & ns_name_map_pair : nodeset_id_name_map)
          error << " " << ns_name_map_pair.first << " : " << ns_name_map_pair.second << "\n";

        paramError("stitch_boundaries_pairs", error.str());
      }
    }

    try
    {
      second = MooseUtils::convert<boundary_id_type>(boundary_pair[1], true);
    }
    catch (...)
    {
      second = meshes[i]->get_boundary_info().get_id_by_name(boundary_pair[1]);

      if (second == BoundaryInfo::invalid_id)
      {
        meshes[i]->print_info();

        std::stringstream error;

        error << "Boundary " << boundary_pair[1] << " doesn't exist on mesh '" << _input_names[i]
              << "' in generator " << name() << "\n";
        error << "Boundary (sideset) names that do exist: \n";
        error << " ID : Name\n";

        auto & sideset_id_name_map = meshes[i]->get_boundary_info().get_sideset_name_map();

        for (auto & ss_name_map_pair : sideset_id_name_map)
          error << " " << ss_name_map_pair.first << " : " << ss_name_map_pair.second << "\n";

        error << "\nBoundary (nodeset) names that do exist: \n";
        error << " ID : Name\n";

        auto & nodeset_id_name_map = mesh->get_boundary_info().get_nodeset_name_map();

        for (auto & ns_name_map_pair : nodeset_id_name_map)
          error << " " << ns_name_map_pair.first << " : " << ns_name_map_pair.second << "\n";

        paramError("stitch_boundaries_pairs", error.str());
      }
    }

    const bool use_binary_search = (_algorithm == "BINARY");

    // Meshes must be prepared to get the global boundary ids
    if (!mesh->is_prepared())
      mesh->prepare_for_use();
    if (!meshes[i]->is_prepared())
      meshes[i]->prepare_for_use();

    // Avoid chaotic boundary merging due to overlapping ids in meshes by simply renumbering the
    // boundaries in the meshes we are going to stitch onto the base mesh
    // This is only done if there is an overlap
    if (_prevent_boundary_ids_overlap)
    {
      const auto & base_mesh_bids = mesh->get_boundary_info().get_global_boundary_ids();
      const auto stitched_mesh_bids = meshes[i]->get_boundary_info().get_global_boundary_ids();

      // Check for an overlap
      bool overlap_found = false;
      for (const auto & bid : stitched_mesh_bids)
        if (base_mesh_bids.count(bid))
          overlap_found = true;

      if (overlap_found)
      {
        const auto max_boundary_id = *base_mesh_bids.rbegin();
        BoundaryID new_index = 1;
        for (const auto bid : stitched_mesh_bids)
        {
          const auto new_bid = max_boundary_id + (new_index++);
          meshes[i]->get_boundary_info().renumber_id(bid, new_bid);
          if (bid == second)
            second = new_bid;
        }
      }
    }
    else
    {
      // If we don't have renumbering, we can get into situations where the same boundary ID is
      // associated with different boundary names. In this case when we stitch, we assign the
      // boundary name of the first mesh to the ID everywhere on the domain. We throw a warning
      // here to warn the user if this is the case.
      const auto & base_mesh_bids = mesh->get_boundary_info().get_global_boundary_ids();
      const auto & other_mesh_bids = meshes[i]->get_boundary_info().get_global_boundary_ids();

      // We check if the same ID is present with different names
      std::set<boundary_id_type> bd_id_intersection;
      std::set_intersection(base_mesh_bids.begin(),
                            base_mesh_bids.end(),
                            other_mesh_bids.begin(),
                            other_mesh_bids.end(),
                            std::inserter(bd_id_intersection, bd_id_intersection.begin()));

      for (const auto bid : bd_id_intersection)
      {
        const auto & sideset_name_on_first_mesh = mesh->get_boundary_info().get_sideset_name(bid);
        const auto & sideset_name_on_second_mesh =
            meshes[i]->get_boundary_info().get_sideset_name(bid);

        if (sideset_name_on_first_mesh != sideset_name_on_second_mesh)
          mooseWarning(
              "Boundary ID ",
              bid,
              " corresponds to different boundary names on the input meshes! On the first "
              "mesh it corresponds to `",
              sideset_name_on_first_mesh,
              "` while on the second mesh it corresponds to `",
              sideset_name_on_second_mesh,
              "`. The final mesh will replace boundary `",
              sideset_name_on_second_mesh,
              "` with `",
              sideset_name_on_first_mesh,
              "`. To avoid this situation, use the `prevent_boundary_ids_overlap` parameter!");
      }
    }

    mesh->stitch_meshes(*meshes[i],
                        first,
                        second,
                        TOLERANCE,
                        _clear_stitched_boundary_ids,
                        getParam<bool>("verbose_stitching"),
                        use_binary_search);

    if (_merge_boundaries_with_same_name)
      MooseMeshUtils::mergeBoundaryIDsWithSameName(*mesh);
  }

  mesh->set_isnt_prepared();
  return dynamic_pointer_cast<MeshBase>(mesh);
}