LocalRelaxationData.cpp

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#include "LocalRelaxationData.hpp"
 
#include <polyfem/mesh/remesh/Remesher.hpp>
#include <polyfem/mesh/remesh/WildRemesher.hpp>
#include <polyfem/assembler/Mass.hpp>
#include <polyfem/solver/forms/ContactForm.hpp>
#include <polyfem/solver/forms/BCLagrangianForm.hpp>
#include <polyfem/solver/forms/BCPenaltyForm.hpp>
#include <polyfem/solver/forms/ContactForm.hpp>
#include <polyfem/solver/problems/StaticBoundaryNLProblem.hpp>
#include <polyfem/time_integrator/ImplicitTimeIntegrator.hpp>
 
namespace polyfem::mesh
{
    template <typename M>
    LocalRelaxationData<M>::LocalRelaxationData(
        const State &state,
        LocalMesh<M> &local_mesh,
        const double current_time,
        const bool contact_enabled)
        : local_mesh(local_mesh)
    {
        problem = std::make_shared<assembler::GenericTensorProblem>("GenericTensor");
 
        init_mesh(state);
        init_bases(state);
        init_boundary_conditions(state);
        init_assembler(state);
        init_mass_matrix(state);
        init_solve_data(state, current_time, contact_enabled);
    }
 
    template <typename M>
    void LocalRelaxationData<M>::init_mesh(const State &)
    {
        POLYFEM_REMESHER_SCOPED_TIMER("LocalRelaxationData::init_mesh");
 
        mesh = Mesh::create(local_mesh.rest_positions(), local_mesh.elements());
        assert(mesh->n_vertices() == local_mesh.num_vertices());
 
        std::vector<int> boundary_ids(mesh->n_boundary_elements(), -1);
        if constexpr (std::is_same_v<M, WildTriRemesher>)
        {
            const auto local_boundary_ids = std::get<Remesher::EdgeMap<int>>(local_mesh.boundary_ids());
            for (int i = 0; i < mesh->n_edges(); i++)
            {
                const size_t e0 = mesh->edge_vertex(i, 0);
                const size_t e1 = mesh->edge_vertex(i, 1);
                boundary_ids[i] = local_boundary_ids.at({{e0, e1}});
            }
        }
        else
        {
            const auto local_boundary_ids = std::get<Remesher::FaceMap<int>>(local_mesh.boundary_ids());
            for (int i = 0; i < mesh->n_faces(); i++)
            {
                std::array<size_t, 3> f = {{
                    (size_t)mesh->face_vertex(i, 0),
                    (size_t)mesh->face_vertex(i, 1),
                    (size_t)mesh->face_vertex(i, 2),
                }};
                boundary_ids[i] = local_boundary_ids.at(f);
            }
        }
 
        mesh->set_boundary_ids(boundary_ids);
        mesh->set_body_ids(local_mesh.body_ids());
    }
 
    template <typename M>
    void LocalRelaxationData<M>::init_bases(const State &state)
    {
        POLYFEM_REMESHER_SCOPED_TIMER("LocalRelaxationData::init_bases");
 
        Eigen::VectorXi vertex_to_basis;
        m_n_bases = Remesher::build_bases(
            *mesh, state.formulation(), bases, local_boundary, vertex_to_basis);
 
        assert(m_n_bases == local_mesh.num_local_vertices());
        m_n_bases = local_mesh.num_vertices(); // the real n_bases includes the global boundary nodes
        assert(vertex_to_basis.size() == m_n_bases);
 
        const int start_i = local_mesh.num_local_vertices();
        if (start_i < m_n_bases)
        {
            // set tail to range [start_i, n_bases)
            std::iota(vertex_to_basis.begin() + start_i, vertex_to_basis.end(), start_i);
        }
 
        assert(std::all_of(vertex_to_basis.begin(), vertex_to_basis.end(), [](const int basis_id) {
            return basis_id >= 0;
        }));
 
        // State::build_node_mapping();
        local_mesh.reorder_vertices(vertex_to_basis);
        problem->update_nodes(vertex_to_basis);
        mesh->update_nodes(vertex_to_basis);
    }
 
    template <typename M>
    void LocalRelaxationData<M>::init_boundary_conditions(const State &state)
    {
        POLYFEM_REMESHER_SCOPED_TIMER("LocalRelaxationData::init_boundary_conditions");
 
        assert(mesh != nullptr);
        state.problem->init(*mesh);
 
        std::vector<int> pressure_boundary_nodes;
        state.problem->setup_bc(
            *mesh, n_bases() - state.obstacle.n_vertices(), bases, /*geom_bases=*/bases,
            /*pressure_bases=*/std::vector<basis::ElementBases>(), local_boundary,
            boundary_nodes, local_neumann_boundary, local_pressure_boundary,
            local_pressure_cavity, pressure_boundary_nodes, dirichlet_nodes, neumann_nodes);
 
        auto find_node_position = [&](const int n_id) {
            for (const auto &bs : bases)
                for (const auto &b : bs.bases)
                    for (const auto &lg : b.global())
                        if (lg.index == n_id)
                            return lg.node;
            log_and_throw_error("Node not found");
        };
 
        // setup nodal values
        dirichlet_nodes_position.resize(dirichlet_nodes.size());
        for (int n = 0; n < dirichlet_nodes.size(); ++n)
            dirichlet_nodes_position[n] = find_node_position(dirichlet_nodes[n]);
 
        neumann_nodes_position.resize(neumann_nodes.size());
        for (int n = 0; n < neumann_nodes.size(); ++n)
            neumann_nodes_position[n] = find_node_position(neumann_nodes[n]);
 
        // Add fixed boundary DOF
        for (const int vi : local_mesh.fixed_vertices())
        {
            for (int d = 0; d < dim(); ++d)
            {
                boundary_nodes.push_back(vi * dim() + d);
            }
        }
 
        std::sort(boundary_nodes.begin(), boundary_nodes.end());
        auto it = std::unique(boundary_nodes.begin(), boundary_nodes.end());
        boundary_nodes.erase(it, boundary_nodes.end());
    }
 
    template <typename M>
    void LocalRelaxationData<M>::init_assembler(const State &state)
    {
        POLYFEM_REMESHER_SCOPED_TIMER("LocalRelaxationData::init_assembler");
        assert(utils::is_param_valid(state.args, "materials"));
 
        assembler = assembler::AssemblerUtils::make_assembler(state.formulation());
        assert(assembler->name() == state.formulation());
        assembler->set_size(dim());
        assembler->set_materials(local_mesh.body_ids(), state.args["materials"], state.units);
 
        mass_matrix_assembler = std::make_shared<assembler::Mass>();
        mass_matrix_assembler->set_size(dim());
        mass_matrix_assembler->set_materials(local_mesh.body_ids(), state.args["materials"], state.units);
 
        pressure_assembler = nullptr; // TODO: implement this
    }
 
    template <typename M>
    void LocalRelaxationData<M>::init_mass_matrix(const State &state)
    {
        POLYFEM_REMESHER_SCOPED_TIMER("LocalRelaxationData::init_mass_matrix");
 
        // Assemble the mass matrix.
        mass_assembly_vals_cache.init(
            is_volume(), bases, /*gbases=*/bases, /*is_mass=*/true);
        assert(mass_matrix_assembler != nullptr);
        mass_matrix_assembler->assemble(
            is_volume(), n_bases(), bases, /*gbases=*/bases,
            mass_assembly_vals_cache,
            /*t=*/0, // TODO: time-dependent mass matrix
            mass, /*is_mass=*/true);
 
        // Set the mass of the codimensional fixed vertices to the average mass.
        const int local_ndof = dim() * local_mesh.num_local_vertices();
        for (int i = local_ndof; i < ndof(); ++i)
            mass.coeffRef(i, i) = state.avg_mass;
    }
 
    template <typename M>
    void LocalRelaxationData<M>::init_solve_data(
        const State &state,
        const double current_time,
        const bool contact_enabled)
    {
        // Current solution.
        const Eigen::MatrixXd target_x = this->sol();
 
        // Assemble the stiffness matrix.
        assembly_vals_cache.init(is_volume(), bases, /*gbases=*/bases, /*is_mass=*/false);
 
        // Create collision mesh.
        if (contact_enabled)
        {
            POLYFEM_REMESHER_SCOPED_TIMER("LocalRelaxationData::init_solve_data -> create collision mesh");
 
            collision_mesh = ipc::CollisionMesh::build_from_full_mesh(
                local_mesh.rest_positions(), local_mesh.boundary_edges(),
                local_mesh.boundary_faces());
 
            // Ignore all collisions between fixed elements.
            std::vector<bool> is_vertex_fixed(local_mesh.num_vertices(), false);
            for (const int vi : local_mesh.fixed_vertices())
                is_vertex_fixed[vi] = true;
            collision_mesh.can_collide = [is_vertex_fixed, this](size_t vi, size_t vj) {
                return !is_vertex_fixed[this->collision_mesh.to_full_vertex_id(vi)]
                       || !is_vertex_fixed[this->collision_mesh.to_full_vertex_id(vj)];
            };
        }
 
        // Initialize time integrator
        if (state.problem->is_time_dependent())
        {
            POLYFEM_REMESHER_SCOPED_TIMER("LocalRelaxationData::init_solve_data -> create time integrator");
            solve_data.time_integrator =
                time_integrator::ImplicitTimeIntegrator::construct_time_integrator(
                    state.args["time"]["integrator"]);
            Eigen::MatrixXd x_prevs, v_prevs, a_prevs;
            Remesher::split_time_integrator_quantities(
                local_mesh.projection_quantities(), dim(), x_prevs, v_prevs, a_prevs);
            solve_data.time_integrator->init(
                x_prevs, v_prevs, a_prevs, state.args["time"]["dt"]);
        }
 
        // Initialize solve_data.rhs_assembler
        {
            POLYFEM_REMESHER_SCOPED_TIMER("LocalRelaxationData::init_solve_data -> create RHS assembler");
 
            json rhs_solver_params = state.args["solver"]["linear"];
            if (!rhs_solver_params.contains("Pardiso"))
                rhs_solver_params["Pardiso"] = {};
            rhs_solver_params["Pardiso"]["mtype"] = -2; // matrix type for Pardiso (2 = SPD)
 
            const int size = state.problem->is_scalar() ? 1 : dim();
            solve_data.rhs_assembler = std::make_shared<assembler::RhsAssembler>(
                *assembler, *mesh, Obstacle(), dirichlet_nodes, neumann_nodes,
                dirichlet_nodes_position, neumann_nodes_position, n_bases(),
                dim(), bases, /*geom_bases=*/bases, mass_assembly_vals_cache,
                *state.problem, state.args["space"]["advanced"]["bc_method"],
                rhs_solver_params);
 
            solve_data.rhs_assembler->assemble(mass_matrix_assembler->density(), rhs);
            rhs *= -1;
        }
 
        std::vector<std::shared_ptr<solver::Form>> forms;
        {
            POLYFEM_REMESHER_SCOPED_TIMER("LocalRelaxationData::init_solve_data -> init forms");
            forms = solve_data.init_forms(
                // General
                state.units, dim(), current_time,
                // Elastic form
                n_bases(), bases, /*geom_bases=*/bases, *assembler,
                assembly_vals_cache, assembly_vals_cache,
                // Body form
                /*n_pressure_bases=*/0, boundary_nodes, local_boundary,
                local_neumann_boundary, state.n_boundary_samples(), rhs,
                target_x, mass_matrix_assembler->density(),
                // Pressure form
                local_pressure_boundary, local_pressure_cavity, pressure_assembler,
                // Inertia form
                state.args.value("/time/quasistatic"_json_pointer, true), mass,
                /*damping_assembler=*/nullptr,
                // Lagged regularization form
                state.args["solver"]["advanced"]["lagged_regularization_weight"],
                state.args["solver"]["advanced"]["lagged_regularization_iterations"],
                // Augmented lagrangian form
                /*obstacle_ndof=*/0,
                // Contact form
                contact_enabled, collision_mesh, state.args["contact"]["dhat"],
                state.avg_mass, state.args["contact"]["use_convergent_formulation"],
                contact_enabled ? state.solve_data.contact_form->barrier_stiffness() : 0,
                state.args["solver"]["contact"]["CCD"]["broad_phase"],
                state.args["solver"]["contact"]["CCD"]["tolerance"],
                state.args["solver"]["contact"]["CCD"]["max_iterations"],
                /*enable_shape_derivatives=*/false,
                // Homogenization
                assembler::MacroStrainValue(),
                // Periodic contact
                /*periodic_contact=*/false, /*tiled_to_single=*/Eigen::VectorXi(),
                // Friction form
                state.args["contact"]["friction_coefficient"],
                state.args["contact"]["epsv"],
                state.args["solver"]["contact"]["friction_iterations"],
                // Rayleigh damping form
                state.args["solver"]["rayleigh_damping"]);
 
            // Remove AL forms because we do not need them in the remeshing process.
            forms.erase(std::remove(forms.begin(), forms.end(), solve_data.al_lagr_form), forms.end());
            forms.erase(std::remove(forms.begin(), forms.end(), solve_data.al_pen_form), forms.end());
            solve_data.al_lagr_form = nullptr;
            solve_data.al_pen_form = nullptr;
        }
 
        solve_data.nl_problem = std::make_shared<polyfem::solver::StaticBoundaryNLProblem>(
            ndof(), boundary_nodes, target_x, forms);
 
        assert(solve_data.time_integrator != nullptr);
        solve_data.nl_problem->update_quantities(current_time, solve_data.time_integrator->x_prev());
        solve_data.nl_problem->init(target_x);
        solve_data.nl_problem->init_lagging(solve_data.time_integrator->x_prev());
        solve_data.nl_problem->update_lagging(target_x, /*iter_num=*/0);
    }
 
    // -------------------------------------------------------------------------
    // Template instantiations
    template class LocalRelaxationData<WildTriRemesher>;
    template class LocalRelaxationData<WildTetRemesher>;
} // namespace polyfem::mesh