SequentialGhostTrackFitter.cc

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#include <vector>

#include "RecoVertex/GhostTrackFitter/interface/GhostTrackState.h"
#include "RecoVertex/GhostTrackFitter/interface/GhostTrackPrediction.h"

#include "RecoVertex/GhostTrackFitter/interface/SequentialGhostTrackFitter.h"

using namespace reco;

namespace {
    static inline double sqr(double arg) { return arg * arg; }
}

SequentialGhostTrackFitter::SequentialGhostTrackFitter() :
    maxIteration(15),
    minDeltaR(0.0015),
    minDistance(0.002),
    weightThreshold(0.001)
{
}

bool SequentialGhostTrackFitter::stable(
                const GhostTrackPrediction &before,
                const GhostTrackPrediction &after) const
{
    return (sqr(after.sz() - before.sz()) +
            sqr(after.ip() - before.ip()) < sqr(minDistance) &&
            sqr(after.eta() - before.eta()) +
            sqr(after.phi() - before.phi()) < sqr(minDeltaR));
}

GhostTrackPrediction SequentialGhostTrackFitter::fit(
            const GhostTrackFitter::PredictionUpdater &updater,
            const GhostTrackPrediction &prior,
            std::vector<GhostTrackState> &states,
            double &ndof, double &chi2)
{
    GhostTrackPrediction pred, lastPred = prior;

    reset();

    ndof = 0.;
    chi2 = 0.;

    unsigned int iteration = 0;
    for(;;) {
        pred = prior;

        if (states.begin() == states.end())
            break;

        if (iteration > 0) {
            for(unsigned int i = 0; i < states.size(); i++) {
                GhostTrackState &state = states[i];
                state.linearize(lastPred);
            }
        }

        ndof = 0.; // prior gives us an initial ndof
        chi2 = 0.;

        for(std::vector<GhostTrackState>::const_iterator state = 
            states.begin(); state != states.end(); ++state) {

            if (state->isValid() &&
                state->weight() > weightThreshold)
                pred = updater.update(pred, *state,
                                      ndof, chi2);
        }

        if (++iteration >= maxIteration || stable(lastPred, pred))
            break;

        postFit(updater, pred, states);

        lastPred = pred;
    }

    return pred;
}