RBF_example_00001.cpp

Generation of RBF object that represents a signed distance function.

Generation of RBF object that represents a signed distance functionbitpit for levelset RBF generation This file explains how to use the script linking the Levelset and RBF capabilities of bitpit to train an RBF collection that represents the signed distance field of STL-defined objects.

Generator script usage: The /examples/RBF_example_00001 executable is the one to use to generate RBFs from .stl files. The syntax to use it is ./RBF_example_00001 <path_to_stl_file> <name_of_stl> <parameters_file>.param.

1. <path_to_stl_file> is the path, absolute or relative, that contains the desired STL file.
2. <name_of_stl> is the name of the STL file. The name must not include the .stl extension.
3. <parameters_file>.param contains as many columns as parameters that must be specified. The first line contains the name of the parameters, and the second line contains the numerical values. All numbers and words on a same line must be separated by . The parameters are nb_subdivision, nb_adapations, radius_ratio, base_function, mesh_range, max_num_threads, tolerance. The parameters have default values, so they don't all have to be in the parameter file. -nb_subdivision dictates the background grid initial refinement. Having a higher number of nb_subdivisions leads to a more precise but more costly RBF. -nb_adaptations dictates the number of adaptive refinement cycles. The RBF will have a higher concentration of nodes around high error zones, which can decrease the training time, the evaluation time and the file size. -radius_ratio dictates the radius that each node has an influence over. This values should be kept low enough so that sharp geometry features are not lost. -base_function dictates the base function type with an integer. The value 2 corresponds to a linear function and produces the lowest error in many cases. -mesh_range dictates how far outside of the STL bounding box the background mesh should extend. Often, a 0.1 value, which represents a 10% increase on each side, is a good choice. -tolerance dictates the expected tolerance when solving the system with all the nodes.

The executable generates two files.

1. RBF_<name_of_stl>.output: this file contains the location of every node and its associated weight, function and support radius.
2. RBF_<name_of_stl>.vtu: this visualization file contains the levelset field of the considered object.

To run: ./RBF_example_00001
To run (with arguments): ./RBF_example_00001 ./ RBF_example_00001 RBF_example_00001.param

#if BITPIT_ENABLE_MPI==1
#include <mpi.h>
#endif
 
#include "bitpit_surfunstructured.hpp"
#include "bitpit_voloctree.hpp"
#include "bitpit_levelset.hpp"
#include "bitpit_LA.hpp"
#include "bitpit_operators.hpp"
#include "bitpit_IO.hpp"
#include "bitpit_RBF.hpp"
#include "bitpit_common.hpp"
 
#include <array>
#include <fstream>
#include <iostream>
#include <string>
#include <vector>
#include <numeric>
#include <algorithm>
#include <iomanip>
 
using namespace std;
using namespace bitpit;
 
void
parse_parameters(std::map<std::string, std::vector<double>> &map,
                 std::string                                 file,
                 const std::string                           delimiter)
{
    // fill a pair, first being a vector of vector name and the second being the
    // vector of vector associated with the vector name.
    std::ifstream myfile(file);
    // open the file.
    if (myfile.is_open())
    {
        std::string              line;
        std::vector<std::string> column_names;
        std::vector<double>      line_of_data;
        unsigned int             line_count = 0;
 
        while (std::getline(myfile, line))
        {
            // read the line and clean the resulting vector.
            std::vector<std::string> list_of_words_base;
 
            std::string s = line;
            size_t pos = 0;
            std::string token;
            while ((pos = s.find(delimiter)) != std::string::npos) {
                token = s.substr(0, pos);
                list_of_words_base.push_back(token);
                s.erase(0, pos + delimiter.length());
            }
            std::vector<std::string> list_of_words_clean;
            for (std::size_t i = 0; i < list_of_words_base.size(); ++i)
            {
                if (list_of_words_base[i] != "")
                {
                    list_of_words_clean.push_back(list_of_words_base[i]);
                }
            }
            // check if the line is contained words or numbers.
            if (line_count != 0)
            {
                line_of_data.resize(list_of_words_clean.size());
                for (std::size_t i = 0; i < line_of_data.size(); i++)
                {
                    line_of_data[i] = std::stod(list_of_words_clean[i]);
                }
                for (std::size_t i = 0; i < line_of_data.size(); ++i)
                {
                    map[column_names[i]].push_back(line_of_data[i]);
                }
            }
            else
            {
                // the line contains words, we assume these are the columns names.
                column_names = list_of_words_clean;
                for (std::size_t i = 0; i < list_of_words_clean.size(); ++i)
                {
                    std::vector<double> base_vector;
                    map[column_names[i]] = base_vector;
                }
            }
            ++line_count;
        }
        myfile.close();
    }
    else
        std::cout << "Unable to open file";
 
    // We add here the default values
    std::vector<std::string> names = {"nb_subdivision",
                                      "nb_adaptions",
                                      "radius_ratio",
                                      "base_function",
                                      "mesh_range",
                                      "tolerance",
                                      "scaling"};
    std::vector<double>      values = {16,
                                       0,
                                       1,
                                       2,
                                       0.2,
                                       1e-8,
                                       1.0};
    for (std::size_t i = 0; i < names.size(); i++)
    {
        if (map.find("f") == map.end())
            map[names[i]].push_back(values[i]);
    }
}
 
void run(std::string filename,
         std::string data_path,
         std::string parameter_file) {
    constexpr int dimensions(3);
 
    // Parsing the parameters
    std::map<std::string, std::vector<double>> parameters;
    parse_parameters(parameters, parameter_file," ");
    int nb_subdivision      = static_cast<int>(parameters["nb_subdivision"][0]);
    int nb_adaptions        = static_cast<int>(parameters["nb_adaptions"][0]);
    double radius_ratio     =                  parameters["radius_ratio"][0];
    int base_function       = static_cast<int>(parameters["base_function"][0]);
    double mesh_range       =                  parameters["mesh_range"][0];
    double TOL              =                  parameters["tolerance"][0];
    double scaling          =                  parameters["scaling"][0];
 
    std::vector<std::string> timers_name;
    std::vector<double> timers_values;
 
    timers_name.push_back("load_geometry");
    double time_start = MPI_Wtime();
 
    //LEVELSET PART
    //Input geometry
#if BITPIT_ENABLE_MPI
    std::unique_ptr<bitpit::SurfUnstructured> STL0(new bitpit::SurfUnstructured(dimensions - 1, MPI_COMM_NULL));
#else
    std::unique_ptr<bitpit::SurfUnstructured> STL0( new bitpit::SurfUnstructured (dimensions - 1) );
#endif
    bitpit::log::cout() << " - Loading stl geometry" << std::endl;
    // Make sure that the STL format is in binary (not ASCII)
    try {
        STL0->importSTL(data_path + filename + ".stl", true);
    }
    catch (const std::bad_alloc &) {
        STL0->importSTL(data_path + filename + ".stl", false);
    }
    STL0->deleteCoincidentVertices();
    STL0->initializeAdjacencies();
    STL0->getVTK().setName("levelset");
    std::array<double, dimensions> center{};
    STL0->scale(scaling,scaling,scaling,center);
    bitpit::log::cout() << "n. vertex: " << STL0->getVertexCount() << std::endl;
    bitpit::log::cout() << "n. simplex: " << STL0->getCellCount() << std::endl;
    // Create initial octree mesh for levelset
    bitpit::log::cout() << " - Setting mesh" << std::endl;
    std::array<double, dimensions> stlMin, stlMax, meshMin, meshMax, delta;
    double h(0.), dh;
    STL0->getBoundingBox(stlMin, stlMax);
    bitpit::log::cout() << " Bounding box minima " << std::endl;
    bitpit::log::cout() << stlMin << std::endl;
    bitpit::log::cout() << " Bounding box maxima " << std::endl;
    bitpit::log::cout() << stlMax << std::endl;
    bitpit::log::cout() << " Bounding box center " << std::endl;
    bitpit::log::cout() << 0.5*(stlMax+stlMin) << std::endl;
 
    delta = stlMax - stlMin;
    meshMin = stlMin - mesh_range * delta;
    meshMax = stlMax + mesh_range * delta;
    for (int i = 0; i < dimensions; ++i) {
        h = std::max(h, meshMax[i] - meshMin[i]);
    }
    dh = h / nb_subdivision;
#if BITPIT_ENABLE_MPI
    bitpit::VolOctree mesh(dimensions, meshMin, h, dh, MPI_COMM_NULL);
#else
    bitpit::VolOctree mesh(dimensions, meshMin, h, dh);
#endif
    mesh.initializeAdjacencies();
    mesh.initializeInterfaces();
    mesh.update();
    mesh.getVTK().setName("RBF_" + filename);
#if BITPIT_ENABLE_MPI
    mesh.setVTKWriteTarget(PatchKernel::WriteTarget::WRITE_TARGET_CELLS_INTERNAL);
#endif
 
    timers_values.push_back(MPI_Wtime() - time_start);
    timers_name.push_back("compute_levelset");
    time_start = MPI_Wtime();
 
 
    // Set levelset configuration
    bitpit::LevelSet levelset;
    levelset.setNarrowBandSize(sqrt(3.0) * h);
    levelset.setMesh(&mesh);
 
    int id0 = levelset.addObject(std::move(STL0), 0);
    const bitpit::LevelSetObject &object0 = levelset.getObject(id0);
    levelset.getObject(id0).setCellBulkEvaluationMode(bitpit::LevelSetBulkEvaluationMode::SIGN_PROPAGATION);
    levelset.getObject(id0).enableVTKOutput(bitpit::LevelSetWriteField::VALUE);
 
    // Write levelset information
    mesh.write();
    bitpit::log::cout() << "Computed levelset within the narrow band... " << std::endl;
 
 
    // Adaptative Refinement
    std::vector<bitpit::adaption::Info> adaptionData_levelset;
    for (int r = 0; r < nb_adaptions; ++r) {
        for (auto &cell: mesh.getCells()) {
            long cellId = cell.getId();
            if (object0.evalCellValue(cellId, false) < mesh.evalCellSize(cellId))
                mesh.markCellForRefinement(cellId);
        }
        adaptionData_levelset = mesh.update(true);
        levelset.update(adaptionData_levelset);
        mesh.write();
    }
    unsigned long nP_total = mesh.getCellCount();
 
 
    timers_values.push_back(MPI_Wtime() - time_start);
    timers_name.push_back("add_nodes_to_RBF");
    time_start = MPI_Wtime();
 
 
    // RBF PART
    bitpit::RBFBasisFunction basisFunction;
    switch (base_function) {
        case 0:
            basisFunction = bitpit::RBFBasisFunction::CUSTOM;
            break;
        case 1:
            basisFunction = bitpit::RBFBasisFunction::WENDLANDC2;
            break;
        case 2:
            basisFunction = bitpit::RBFBasisFunction::LINEAR;
            break;
        case 3:
            basisFunction = bitpit::RBFBasisFunction::GAUSS90;
            break;
        case 4:
            basisFunction = bitpit::RBFBasisFunction::GAUSS95;
            break;
        case 5:
            basisFunction = bitpit::RBFBasisFunction::GAUSS99;
            break;
        case 6:
            basisFunction = bitpit::RBFBasisFunction::C1C0;
            break;
        case 7:
            basisFunction = bitpit::RBFBasisFunction::C2C0;
            break;
        case 8:
            basisFunction = bitpit::RBFBasisFunction::C0C1;
            break;
        case 9:
            basisFunction = bitpit::RBFBasisFunction::C1C1;
            break;
        case 10:
            basisFunction = bitpit::RBFBasisFunction::C2C1;
            break;
        case 11:
            basisFunction = bitpit::RBFBasisFunction::C0C2;
            break;
        case 12:
            basisFunction = bitpit::RBFBasisFunction::C1C2;
            break;
        case 13:
            basisFunction = bitpit::RBFBasisFunction::C2C2;
            break;
        case 14:
            basisFunction = bitpit::RBFBasisFunction::COSINUS;
            break;
        default:
            basisFunction = bitpit::RBFBasisFunction::LINEAR;
            break;
    }
    std::vector<double> values;
    std::vector<double> weights;
    std::vector<double> radii;
    std::vector<std::array<double, dimensions>> nodes;
    values.resize(nP_total);
    weights.resize(nP_total);
    nodes.resize(nP_total);
    radii.resize(nP_total);
 
    bitpit::RBF RBFObject;
    RBFObject.setMode(bitpit::RBFMode::PARAM);
    RBFObject.setFunction(basisFunction);
 
    bitpit::log::cout() << "Adding nodes to the RBF" << std::endl;
    for (size_t it_RBF = 0; it_RBF < nP_total; it_RBF++) {
        nodes[it_RBF] = mesh.evalCellCentroid(it_RBF);
        values[it_RBF] = levelset.getObject(id0).evalCellValue(it_RBF, true);
        RBFObject.addNode(nodes[it_RBF]);
        radii[it_RBF] = mesh.evalCellSize(it_RBF) * radius_ratio;
    }
    RBFObject.setSupportRadius(radii);
 
    timers_values.push_back(MPI_Wtime() - time_start);
    timers_name.push_back("fill_matrix");
    time_start = MPI_Wtime();
 
    // Training the RBF
    bitpit::log::cout() << "Training RBFObject" << std::endl;
    // Initializing the matrix and vector
    int nNZ = nP_total*(1+(2*(int)ceil(radius_ratio)^dimensions));
#if BITPIT_ENABLE_MPI==1
    SparseMatrix A(MPI_COMM_WORLD, true, nP_total, nP_total, nNZ);
#else
    SparseMatrix A(nP_total, nP_total, nNZ);
#endif
 
    std::vector<long> rowPattern;
    std::vector<double> rowValues;
    // Compute the values for A
    bitpit::log::cout() << "Filling the matrix" << std::endl;
    for (unsigned long i = 0; i < nP_total; i++) {
        for (unsigned long j = 0; j < nP_total; j++) {
            double v_ij = RBFObject.evalBasisPair(i,j);
            if (abs(v_ij) > TOL) {
                rowPattern.push_back(j);
                rowValues.push_back(v_ij);
            }
        }
        A.addRow(rowPattern, rowValues);
        rowPattern.clear();
        rowValues.clear();
    }
    A.assembly();
 
    SystemSolver system;
    system.assembly(A);
 
    timers_values.push_back(MPI_Wtime() - time_start);
    timers_name.push_back("fill_RHS");
    time_start = MPI_Wtime();
 
    double *b = system.getRHSRawPtr();
    // Compute the values for b
    bitpit::log::cout() << "Filling the RHS" << std::endl;
    for (unsigned long i = 0; i < nP_total; ++i) {
        b[i] = values[i];
    }
    system.restoreRHSRawPtr(b);
 
    timers_values.push_back(MPI_Wtime() - time_start);
    timers_name.push_back("solve_system");
    time_start = MPI_Wtime();
 
    bitpit::log::cout() << "Solving the system" << std::endl;
 
    double *initialSolution = system.getSolutionRawPtr();
    for (unsigned long i = 0; i < nP_total; ++i) {
        initialSolution[i] = values[i];
    }
    system.restoreSolutionRawPtr(initialSolution);
 
    system.solve();
    const double *x = system.getSolutionRawReadPtr();
    bitpit::log::cout() << "Solved system" << std::endl;
 
    timers_values.push_back(MPI_Wtime() - time_start);
    timers_name.push_back("add_weights_to_RBFObject");
    time_start = MPI_Wtime();
 
    bitpit::log::cout() << "Adding weights to RBFObject" << std::endl;
    for (unsigned long i = 0; i < nP_total; i++) {
        weights[i] = x[i];
    }
    system.restoreSolutionRawPtr(initialSolution);
    RBFObject.addData(weights);
    bitpit::log::cout() << "Added weights to RBFObject" << std::endl;
    bitpit::log::cout() << "Finished RBF training" << std::endl;
 
    std::size_t nMaxCellVertices = mesh.getCell(0).getVertexIds().size();
 
    timers_values.push_back(MPI_Wtime()-time_start);
    timers_name.push_back("output_RBF_and_analytical");
    time_start = MPI_Wtime();
 
    // RBF Output
    bitpit::log::cout() << "Outputting" << std::endl;
    std::vector<double> display_values;
    display_values.resize(nP_total);
 
    BITPIT_CREATE_WORKSPACE(vertexCoordinates, std::array<double BITPIT_COMMA dimensions>, nMaxCellVertices,
                            ReferenceElementInfo::MAX_ELEM_VERTICES)
    const PatchKernel::CellConstRange &cellWriteRange = mesh.getVTKCellWriteRange();
    for (const Cell &cell:cellWriteRange){
        const unsigned long global_id = cell.getId();
        mesh.getCellVertexCoordinates(global_id, vertexCoordinates);
        std::array<double, dimensions> point = cell.evalCentroid(vertexCoordinates);
        std::vector<double> temp_disp = RBFObject.evalRBF(point);
        display_values[global_id] = temp_disp[0]; //Only the first field is used, since there is only one
    }
    mesh.getVTK().addData<double>("RBF", VTKFieldType::SCALAR, VTKLocation::CELL, display_values);
    mesh.write();
 
    timers_values.push_back(MPI_Wtime()-time_start);
    timers_name.push_back("output_RBF_to_file");
    time_start = MPI_Wtime();
 
    //Outputting the combined RBF to a txt file
    ofstream fw("RBF_" + filename + ".output", std::ofstream::ate);
    if (fw.is_open()) {
        fw << "support_radius basis_function node_x node_y ";
        if (dimensions == 3)
        {
            fw << "node_z ";
        }
        fw << "weight \n";
        for (unsigned long line = 0; line < nP_total; line++) {
            // Set precision
            int PRECISION = 20; //number of decimals
            std::ostringstream streamObj_support_radius;
            std::ostringstream streamObj_x;
            std::ostringstream streamObj_y;
            std::ostringstream streamObj_z;
            std::ostringstream streamObj_weight;
            streamObj_support_radius << std::fixed;
            streamObj_x              << std::fixed;
            streamObj_y              << std::fixed;
            streamObj_z              << std::fixed;
            streamObj_weight         << std::fixed;
            streamObj_support_radius << std::setprecision(PRECISION);
            streamObj_x              << std::setprecision(PRECISION);
            streamObj_y              << std::setprecision(PRECISION);
            streamObj_z              << std::setprecision(PRECISION);
            streamObj_weight         << std::setprecision(PRECISION);
            streamObj_support_radius << radii[line];
            streamObj_x << nodes[line][0];
            streamObj_y << nodes[line][1];
            streamObj_z << nodes[line][2];
            streamObj_weight << weights[line];
            std::string strObj_support_radius = streamObj_support_radius.str();
            std::string strObj_x              = streamObj_x.str();
            std::string strObj_y              = streamObj_y.str();
            std::string strObj_z              = streamObj_z.str();
            std::string strObj_weight         = streamObj_weight.str();
            fw << strObj_support_radius << " " << base_function << " "<<
                  strObj_x << " " << strObj_y << " ";
            if (dimensions == 3)
            {
                fw << strObj_z << " ";
            }
            fw << strObj_weight << " ";
            if (line < nP_total -1)
                fw << "\n";
        }
        fw.close();
    } else bitpit::log::cout() << "Problem with opening file" << std::endl;
    bitpit::log::cout() << "Finished outputting" << std::endl;
 
    timers_values.push_back(MPI_Wtime()-time_start);
 
    int nb_timers = timers_name.size();
    bitpit::log::cout()<< std::endl << "Timers" << std::endl;
    for (int t = 0; t < nb_timers; t++)
    {
        bitpit::log::cout() << timers_name.at(t) << ":" << timers_values.at(t) << std::endl;
    }
}
 
int main(int argc, char *argv[])
{
    int nProcs = 1;
    int rank   = 0;
 
#if BITPIT_ENABLE_MPI==1
    MPI_Init(&argc,&argv);
    MPI_Comm_size(MPI_COMM_WORLD, &nProcs);
    MPI_Comm_rank(MPI_COMM_WORLD, &rank);
    if (nProcs>1)
    {
        bitpit::log::cout() << "nProcs > 1 isn't supported at the moment" << std::endl;
        exit(1);
    }
#endif
 
    // Arguments
    std::vector<std::string> argList;
    for(int i=0;i<argc;i++)
        argList.emplace_back(argv[i]);
 
    // Default values
    std::string data_path      = "../test/integration_tests/levelset/data/";
    std::string filename       = "cube";
    std::string parameter_file = "RBF_example_00001.param";
    if (argc > 3)
    {
        data_path      = argList[1];
        filename       = argList[2];
        parameter_file = argList[3];
    }
 
    // Initialize the logger
    log::manager().initialize(log::MODE_COMBINE, true, nProcs, rank);
    log::cout() << log::fileVerbosity(log::LEVEL_INFO);
    log::cout() << log::disableConsole();
 
    // Run the example
    try {
        run(filename,
            data_path,
            parameter_file);
    }
    catch (const std::exception &exception) {
    log::cout() << exception.what();
    exit(1);
    }
 
#if BITPIT_ENABLE_MPI==1
    MPI_Finalize();
#endif
    return 0;
}