CPointPDFSOG.cpp

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/* +------------------------------------------------------------------------+
   |                     Mobile Robot Programming Toolkit (MRPT)            |
   |                          http://www.mrpt.org/                          |
   |                                                                        |
   | Copyright (c) 2005-2018, Individual contributors, see AUTHORS file     |
   | See: http://www.mrpt.org/Authors - All rights reserved.                |
   | Released under BSD License. See details in http://www.mrpt.org/License |
   +------------------------------------------------------------------------+ */
 
#include "poses-precomp.h"  // Precompiled headers
 
#include <mrpt/poses/CPointPDFSOG.h>
#include <mrpt/poses/CPosePDF.h>
#include <mrpt/poses/CPose3D.h>
#include <mrpt/bayes/CParticleFilterCapable.h>
#include <mrpt/random.h>
#include <mrpt/math/distributions.h>
#include <mrpt/math/matrix_serialization.h>
#include <mrpt/serialization/CArchive.h>
#include <mrpt/system/os.h>
 
using namespace mrpt::poses;
using namespace mrpt::math;
 
using namespace mrpt::bayes;
using namespace mrpt::random;
using namespace mrpt::system;
using namespace std;
 
IMPLEMENTS_SERIALIZABLE(CPointPDFSOG, CPosePDF, mrpt::poses)
 
/*---------------------------------------------------------------
    Constructor
  ---------------------------------------------------------------*/
CPointPDFSOG::CPointPDFSOG(size_t nModes) : m_modes(nModes) {}
/*---------------------------------------------------------------
            clear
  ---------------------------------------------------------------*/
void CPointPDFSOG::clear() { m_modes.clear(); }
/*---------------------------------------------------------------
    Resize
  ---------------------------------------------------------------*/
void CPointPDFSOG::resize(const size_t N) { m_modes.resize(N); }
/*---------------------------------------------------------------
                        getMean
  Returns an estimate of the pose, (the mean, or mathematical expectation of the
 PDF)
 ---------------------------------------------------------------*/
void CPointPDFSOG::getMean(CPoint3D& p) const
{
    size_t N = m_modes.size();
    double X = 0, Y = 0, Z = 0;
 
    if (N)
    {
        CListGaussianModes::const_iterator it;
        double sumW = 0;
 
        for (it = m_modes.begin(); it != m_modes.end(); ++it)
        {
            double w;
            sumW += w = exp(it->log_w);
            X += it->val.mean.x() * w;
            Y += it->val.mean.y() * w;
            Z += it->val.mean.z() * w;
        }
        if (sumW > 0)
        {
            X /= sumW;
            Y /= sumW;
            Z /= sumW;
        }
    }
 
    p.x(X);
    p.y(Y);
    p.z(Z);
}
 
/*---------------------------------------------------------------
                        getCovarianceAndMean
 ---------------------------------------------------------------*/
void CPointPDFSOG::getCovarianceAndMean(
    CMatrixDouble33& estCov, CPoint3D& p) const
{
    size_t N = m_modes.size();
 
    getMean(p);
    estCov.zeros();
 
    if (N)
    {
        // 1) Get the mean:
        double sumW = 0;
        CMatrixDouble31 estMean = CMatrixDouble31(p);
 
        CListGaussianModes::const_iterator it;
 
        CMatrixDouble33 partCov;
 
        for (it = m_modes.begin(); it != m_modes.end(); ++it)
        {
            double w;
            sumW += w = exp(it->log_w);
 
            // estCov += w * ( it->val.cov +
            // ((estMean_i-estMean)*(~(estMean_i-estMean))) );
            CMatrixDouble31 estMean_i = CMatrixDouble31(it->val.mean);
            estMean_i -= estMean;
            partCov.multiply_AAt(estMean_i);
            partCov += it->val.cov;
            partCov *= w;
            estCov += partCov;
        }
 
        if (sumW != 0) estCov *= (1.0 / sumW);
    }
}
 
uint8_t CPointPDFSOG::serializeGetVersion() const { return 1; }
void CPointPDFSOG::serializeTo(mrpt::serialization::CArchive& out) const
{
    uint32_t N = m_modes.size();
    out << N;
    for (const auto& m : m_modes)
    {
        out << m.log_w;
        out << m.val.mean;
        mrpt::math::serializeSymmetricMatrixTo(m.val.cov, out);
    }
}
void CPointPDFSOG::serializeFrom(
    mrpt::serialization::CArchive& in, uint8_t version)
{
    switch (version)
    {
        case 0:
        case 1:
        {
            uint32_t N;
            in >> N;
            this->resize(N);
            for (auto& m : m_modes)
            {
                in >> m.log_w;
 
                // In version 0, weights were linear!!
                if (version == 0) m.log_w = log(max(1e-300, m.log_w));
 
                in >> m.val.mean;
                mrpt::math::deserializeSymmetricMatrixFrom(m.val.cov, in);
            }
        }
        break;
        default:
            MRPT_THROW_UNKNOWN_SERIALIZATION_VERSION(version)
    };
}
 
void CPointPDFSOG::copyFrom(const CPointPDF& o)
{
    MRPT_START
 
    if (this == &o) return;  // It may be used sometimes
 
    if (o.GetRuntimeClass() == CLASS_ID(CPointPDFSOG))
    {
        m_modes = static_cast<const CPointPDFSOG*>(&o)->m_modes;
    }
    else
    {
        // Approximate as a mono-modal gaussian pdf:
        this->resize(1);
        m_modes[0].log_w = 0;
        o.getCovarianceAndMean(m_modes[0].val.cov, m_modes[0].val.mean);
    }
 
    MRPT_END
}
 
/*---------------------------------------------------------------
                        saveToTextFile
  ---------------------------------------------------------------*/
bool CPointPDFSOG::saveToTextFile(const std::string& file) const
{
    FILE* f = os::fopen(file.c_str(), "wt");
    if (!f) return false;
 
    for (CListGaussianModes::const_iterator it = m_modes.begin();
         it != m_modes.end(); ++it)
        os::fprintf(
            f, "%e %e %e %e %e %e %e %e %e %e\n", exp(it->log_w),
            it->val.mean.x(), it->val.mean.y(), it->val.mean.z(),
            it->val.cov(0, 0), it->val.cov(1, 1), it->val.cov(2, 2),
            it->val.cov(0, 1), it->val.cov(0, 2), it->val.cov(1, 2));
    os::fclose(f);
    return true;
}
 
/*---------------------------------------------------------------
                        changeCoordinatesReference
 ---------------------------------------------------------------*/
void CPointPDFSOG::changeCoordinatesReference(const CPose3D& newReferenceBase)
{
    for (auto& m : m_modes) m.val.changeCoordinatesReference(newReferenceBase);
}
 
/*---------------------------------------------------------------
                    drawSingleSample
 ---------------------------------------------------------------*/
void CPointPDFSOG::drawSingleSample(CPoint3D& outSample) const
{
    MRPT_START
 
    ASSERT_(m_modes.size() > 0);
 
    // 1st: Select a mode with a probability proportional to its weight:
    vector<double> logWeights(m_modes.size());
    vector<size_t> outIdxs;
    vector<double>::iterator itW;
    CListGaussianModes::const_iterator it;
    for (it = m_modes.begin(), itW = logWeights.begin(); it != m_modes.end();
         ++it, ++itW)
        *itW = it->log_w;
 
    CParticleFilterCapable::computeResampling(
        CParticleFilter::prMultinomial,  // Resampling algorithm
        logWeights,  // input: log weights
        outIdxs  // output: indexes
        );
 
    // we need just one: take the first (arbitrary)
    size_t selectedIdx = outIdxs[0];
    ASSERT_(selectedIdx < m_modes.size());
    const CPointPDFGaussian* selMode = &m_modes[selectedIdx].val;
 
    // 2nd: Draw a position from the selected Gaussian:
    CVectorDouble vec;
    getRandomGenerator().drawGaussianMultivariate(vec, selMode->cov);
 
    ASSERT_(vec.size() == 3);
    outSample.x(selMode->mean.x() + vec[0]);
    outSample.y(selMode->mean.y() + vec[1]);
    outSample.z(selMode->mean.z() + vec[2]);
 
    MRPT_END
}
 
/*---------------------------------------------------------------
                    bayesianFusion
 ---------------------------------------------------------------*/
void CPointPDFSOG::bayesianFusion(
    const CPointPDF& p1_, const CPointPDF& p2_,
    const double minMahalanobisDistToDrop)
{
    MRPT_START
 
    // p1: CPointPDFSOG, p2: CPosePDFGaussian:
 
    ASSERT_(p1_.GetRuntimeClass() == CLASS_ID(CPointPDFSOG));
    ASSERT_(p2_.GetRuntimeClass() == CLASS_ID(CPointPDFSOG));
 
    const CPointPDFSOG* p1 = static_cast<const CPointPDFSOG*>(&p1_);
    const CPointPDFSOG* p2 = static_cast<const CPointPDFSOG*>(&p2_);
 
    // Compute the new kernel means, covariances, and weights after multiplying
    // to the Gaussian "p2":
    CPointPDFGaussian auxGaussianProduct, auxSOG_Kernel_i;
 
    float minMahalanobisDistToDrop2 = square(minMahalanobisDistToDrop);
 
    this->m_modes.clear();
    bool is2D =
        false;  // to detect & avoid errors in 3x3 matrix inversions of range=2.
 
    for (CListGaussianModes::const_iterator it1 = p1->m_modes.begin();
         it1 != p1->m_modes.end(); ++it1)
    {
        CMatrixDouble33 c = it1->val.cov;
 
        // Is a 2D covariance??
        if (c.get_unsafe(2, 2) == 0)
        {
            is2D = true;
            c.set_unsafe(2, 2, 1);
        }
 
        ASSERT_(c(0, 0) != 0 && c(0, 0) != 0);
 
        CMatrixDouble33 covInv(UNINITIALIZED_MATRIX);
        c.inv(covInv);
 
        CMatrixDouble31 eta = covInv * CMatrixDouble31(it1->val.mean);
 
        // Normal distribution canonical form constant:
        // See: http://www-static.cc.gatech.edu/~wujx/paper/Gaussian.pdf
        double a = -0.5 * (3 * log(M_2PI) - log(covInv.det()) +
                           eta.multiply_HtCH_scalar(
                               c));  // (~eta * (*it1).val.cov * eta)(0,0) );
 
        for (CListGaussianModes::const_iterator it2 = p2->m_modes.begin();
             it2 != p2->m_modes.end(); ++it2)
        {
            auxSOG_Kernel_i = (*it2).val;
            if (auxSOG_Kernel_i.cov.get_unsafe(2, 2) == 0)
            {
                auxSOG_Kernel_i.cov.set_unsafe(2, 2, 1);
                is2D = true;
            }
            ASSERT_(
                auxSOG_Kernel_i.cov(0, 0) > 0 && auxSOG_Kernel_i.cov(1, 1) > 0);
 
            // Should we drop this product term??
            bool reallyComputeThisOne = true;
            if (minMahalanobisDistToDrop > 0)
            {
                // Approximate (fast) mahalanobis distance (square):
                float mahaDist2;
 
                float stdX2 =
                    max(auxSOG_Kernel_i.cov.get_unsafe(0, 0),
                        (*it1).val.cov.get_unsafe(0, 0));
                mahaDist2 =
                    square(auxSOG_Kernel_i.mean.x() - (*it1).val.mean.x()) /
                    stdX2;
 
                float stdY2 =
                    max(auxSOG_Kernel_i.cov.get_unsafe(1, 1),
                        (*it1).val.cov.get_unsafe(1, 1));
                mahaDist2 +=
                    square(auxSOG_Kernel_i.mean.y() - (*it1).val.mean.y()) /
                    stdY2;
 
                if (!is2D)
                {
                    float stdZ2 =
                        max(auxSOG_Kernel_i.cov.get_unsafe(2, 2),
                            (*it1).val.cov.get_unsafe(2, 2));
                    mahaDist2 +=
                        square(auxSOG_Kernel_i.mean.z() - (*it1).val.mean.z()) /
                        stdZ2;
                }
 
                reallyComputeThisOne = mahaDist2 < minMahalanobisDistToDrop2;
            }
 
            if (reallyComputeThisOne)
            {
                auxGaussianProduct.bayesianFusion(auxSOG_Kernel_i, (*it1).val);
 
                // ----------------------------------------------------------------------
                // The new weight is given by:
                //
                //   w'_i = w_i * exp( a + a_i - a' )
                //
                //      a = -1/2 ( dimensionality * log(2pi) - log(det(Cov^-1))
                //      + (Cov^-1 * mu)^t * Cov^-1 * (Cov^-1 * mu) )
                //
                // ----------------------------------------------------------------------
                TGaussianMode newKernel;
 
                newKernel.val = auxGaussianProduct;  // Copy mean & cov
 
                CMatrixDouble33 covInv_i = auxSOG_Kernel_i.cov.inv();
                CMatrixDouble31 eta_i = CMatrixDouble31(auxSOG_Kernel_i.mean);
                eta_i = covInv_i * eta_i;
 
                CMatrixDouble33 new_covInv_i = newKernel.val.cov.inv();
                CMatrixDouble31 new_eta_i = CMatrixDouble31(newKernel.val.mean);
                new_eta_i = new_covInv_i * new_eta_i;
 
                double a_i =
                    -0.5 *
                    (3 * log(M_2PI) - log(new_covInv_i.det()) +
                     (eta_i.adjoint() * auxSOG_Kernel_i.cov * eta_i)(0, 0));
                double new_a_i =
                    -0.5 * (3 * log(M_2PI) - log(new_covInv_i.det()) +
                            (new_eta_i.adjoint() * newKernel.val.cov *
                             new_eta_i)(0, 0));
 
                newKernel.log_w =
                    (it1)->log_w + (it2)->log_w + a + a_i - new_a_i;
 
                // Fix 2D case:
                if (is2D) newKernel.val.cov(2, 2) = 0;
 
                // Add to the results (in "this") the new kernel:
                this->m_modes.push_back(newKernel);
            }  // end if reallyComputeThisOne
        }  // end for it2
 
    }  // end for it1
 
    normalizeWeights();
 
    MRPT_END
}
 
/*---------------------------------------------------------------
                        assureSymmetry
 ---------------------------------------------------------------*/
void CPointPDFSOG::assureSymmetry()
{
    MRPT_START
    // Differences, when they exist, appear in the ~15'th significant
    //  digit, so... just take one of them arbitrarily!
    for (CListGaussianModes::iterator it = m_modes.begin(); it != m_modes.end();
         ++it)
    {
        it->val.cov(0, 1) = it->val.cov(1, 0);
        it->val.cov(0, 2) = it->val.cov(2, 0);
        it->val.cov(1, 2) = it->val.cov(2, 1);
    }
 
    MRPT_END
}
 
/*---------------------------------------------------------------
                        normalizeWeights
 ---------------------------------------------------------------*/
void CPointPDFSOG::normalizeWeights()
{
    MRPT_START
 
    if (!m_modes.size()) return;
 
    CListGaussianModes::iterator it;
    double maxW = m_modes[0].log_w;
    for (it = m_modes.begin(); it != m_modes.end(); ++it)
        maxW = max(maxW, it->log_w);
 
    for (it = m_modes.begin(); it != m_modes.end(); ++it) it->log_w -= maxW;
 
    MRPT_END
}
 
/*---------------------------------------------------------------
                        ESS
 ---------------------------------------------------------------*/
double CPointPDFSOG::ESS() const
{
    MRPT_START
    CListGaussianModes::const_iterator it;
    double cum = 0;
 
    /* Sum of weights: */
    double sumLinearWeights = 0;
    for (it = m_modes.begin(); it != m_modes.end(); ++it)
        sumLinearWeights += exp(it->log_w);
 
    /* Compute ESS: */
    for (it = m_modes.begin(); it != m_modes.end(); ++it)
        cum += square(exp(it->log_w) / sumLinearWeights);
 
    if (cum == 0)
        return 0;
    else
        return 1.0 / (m_modes.size() * cum);
    MRPT_END
}
 
/*---------------------------------------------------------------
                        evaluatePDFInArea
 ---------------------------------------------------------------*/
void CPointPDFSOG::evaluatePDFInArea(
    float x_min, float x_max, float y_min, float y_max, float resolutionXY,
    float z, CMatrixD& outMatrix, bool sumOverAllZs)
{
    MRPT_START
 
    ASSERT_(x_max > x_min);
    ASSERT_(y_max > y_min);
    ASSERT_(resolutionXY > 0);
 
    const size_t Nx = (size_t)ceil((x_max - x_min) / resolutionXY);
    const size_t Ny = (size_t)ceil((y_max - y_min) / resolutionXY);
    outMatrix.setSize(Ny, Nx);
 
    for (size_t i = 0; i < Ny; i++)
    {
        const float y = y_min + i * resolutionXY;
        for (size_t j = 0; j < Nx; j++)
        {
            float x = x_min + j * resolutionXY;
            outMatrix(i, j) = evaluatePDF(CPoint3D(x, y, z), sumOverAllZs);
        }
    }
 
    MRPT_END
}
 
/*---------------------------------------------------------------
                        evaluatePDF
 ---------------------------------------------------------------*/
double CPointPDFSOG::evaluatePDF(const CPoint3D& x, bool sumOverAllZs) const
{
    if (!sumOverAllZs)
    {
        // Normal evaluation:
        CMatrixDouble31 X = CMatrixDouble31(x);
        double ret = 0;
 
        CMatrixDouble31 MU;
 
        for (CListGaussianModes::const_iterator it = m_modes.begin();
             it != m_modes.end(); ++it)
        {
            MU = CMatrixDouble31(it->val.mean);
            ret += exp(it->log_w) * math::normalPDF(X, MU, it->val.cov);
        }
 
        return ret;
    }
    else
    {
        // Only X,Y:
        CMatrixD X(2, 1), MU(2, 1), COV(2, 2);
        double ret = 0;
 
        X(0, 0) = x.x();
        X(1, 0) = x.y();
 
        for (CListGaussianModes::const_iterator it = m_modes.begin();
             it != m_modes.end(); ++it)
        {
            MU(0, 0) = it->val.mean.x();
            MU(1, 0) = it->val.mean.y();
 
            COV(0, 0) = it->val.cov(0, 0);
            COV(1, 1) = it->val.cov(1, 1);
            COV(0, 1) = COV(1, 0) = it->val.cov(0, 1);
 
            ret += exp(it->log_w) * math::normalPDF(X, MU, COV);
        }
 
        return ret;
    }
}
 
/*---------------------------------------------------------------
                        getMostLikelyMode
 ---------------------------------------------------------------*/
void CPointPDFSOG::getMostLikelyMode(CPointPDFGaussian& outVal) const
{
    if (this->empty())
    {
        outVal = CPointPDFGaussian();
    }
    else
    {
        const_iterator it_best = m_modes.end();
        for (const_iterator it = m_modes.begin(); it != m_modes.end(); ++it)
            if (it_best == m_modes.end() || it->log_w > it_best->log_w)
                it_best = it;
 
        outVal = it_best->val;
    }
}
 
/*---------------------------------------------------------------
                        getAs3DObject
 ---------------------------------------------------------------*/
// void  CPointPDFSOG::getAs3DObject( mrpt::opengl::CSetOfObjects::Ptr  &outObj
// )
// const
//{
//  // For each gaussian node
//  for (CListGaussianModes::const_iterator it = m_modes.begin(); it!=
// m_modes.end();++it)
//  {
//      opengl::CEllipsoid::Ptr obj =
// mrpt::make_aligned_shared<opengl::CEllipsoid>();
//
//      obj->setPose( it->val.mean);
//      obj->setCovMatrix(it->val.cov,  it->val.cov(2,2)==0  ?  2:3);
//
//      obj->setQuantiles(3);
//      obj->enableDrawSolid3D(false);
//      obj->setColor(1,0,0, 0.5);
//
//      outObj->insert( obj );
//  } // end for each gaussian node
//}