Example: bayes_rejection_sampling_example

C++ example source code:

/* +------------------------------------------------------------------------+
   |                     Mobile Robot Programming Toolkit (MRPT)            |
   |                          https://www.mrpt.org/                         |
   |                                                                        |
   | Copyright (c) 2005-2021, Individual contributors, see AUTHORS file     |
   | See: https://www.mrpt.org/Authors - All rights reserved.               |
   | Released under BSD License. See: https://www.mrpt.org/License          |
   +------------------------------------------------------------------------+ */

#include <mrpt/bayes.h>
#include <mrpt/poses/CPoint2D.h>
#include <mrpt/poses/CPose2D.h>
#include <mrpt/random.h>
#include <mrpt/system/CTicTac.h>
#include <mrpt/system/os.h>

#include <iostream>

using namespace mrpt;
using namespace mrpt::bayes;
using namespace mrpt::poses;
using namespace mrpt::random;
using namespace mrpt::system;

double SIGMA = 0.05;

// The custom class:
class CMyRejectionSampling : public CRejectionSamplingCapable<CPose2D>
{
   protected:
    void RS_drawFromProposal(CPose2D& outSample) override
    {
        double ang = getRandomGenerator().drawUniform(-M_PI, M_PI);
        double R = getRandomGenerator().drawGaussian1D(1.0, SIGMA);
        outSample.x(1.0f - cos(ang) * R);
        outSample.y(sin(ang) * R);
        outSample.phi(getRandomGenerator().drawUniform(-M_PI, M_PI));
    }

    double RS_observationLikelihood(const CPose2D& x) override
    {
        return exp(
            -0.5 * square((x.distanceTo(CPoint2D(0, 0)) - 1.0f) / SIGMA));
    }
};

// ------------------------------------------------------
//              TestRS
// ------------------------------------------------------
void TestRS()
{
    CMyRejectionSampling RS;
    std::vector<CMyRejectionSampling::TParticle> samples;
    CTicTac tictac;

    tictac.Tic();
    printf("Computing...");

    RS.rejectionSampling(1000, samples);

    printf("Ok! %fms\n", 1000 * tictac.Tac());

    FILE* f = os::fopen("_out_samples.txt", "wt");
    std::vector<CMyRejectionSampling::TParticle>::iterator it;
    for (it = samples.begin(); it != samples.end(); it++)
        os::fprintf(
            f, "%f %f %f %e\n", it->d->x(), it->d->y(), it->d->phi(),
            it->log_w);

    os::fclose(f);
}

// ------------------------------------------------------
//                      MAIN
// ------------------------------------------------------
int main()
{
    try
    {
        TestRS();

        return 0;
    }
    catch (const std::exception& e)
    {
        std::cerr << "MRPT error: " << mrpt::exception_to_str(e) << std::endl;
        return -1;
    }
    catch (...)
    {
        printf("Untyped excepcion!!");
        return -1;
    }
}