/data/refman/pasoursint/CMSSW_4_1_8_patch12/src/RecoTracker/SiTrackerMRHTools/src/MeasurementByLayerGrouper.cc

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#include "RecoTracker/SiTrackerMRHTools/interface/MeasurementByLayerGrouper.h"
#include "TrackingTools/DetLayers/interface/DetLayer.h"
#include "TrackingTools/PatternTools/interface/TrajectoryMeasurement.h"
#include "RecoTracker/TkDetLayers/interface/GeometricSearchTracker.h"
#include "FWCore/Utilities/interface/Exception.h"
#include "FWCore/MessageLogger/interface/MessageLogger.h"

//#define debug_MeasurementByLayerGrouper_ 

using namespace std;

vector<pair<const DetLayer*, vector<TrajectoryMeasurement> > > MeasurementByLayerGrouper::operator()(const vector<TM>& vtm) const{
        if(vtm.empty()) 
                return vector<pair<const DetLayer*, vector<TM> > >();

        vector<pair<const DetLayer*, vector<TM> > > result;
        result.reserve(vtm.size());

        vector<TM>::const_iterator start = vtm.begin();
        //here we assume that the TM on the same detLayer are consecutive (as it should)
        while(start != vtm.end()) {
                vector<TM>::const_iterator ipart = start;
                do {ipart++;}
                while(ipart != vtm.end() && 
                        getDetLayer(*start)==getDetLayer(*ipart) &&
                        getDetLayer(*start) != 0  //the returned pointer will be 0 in case
                                                  //the measurement contains an invalid hit with no associated detid.
                                                  //This kind of hits are at most one per layer.
                                                  //this last condition avoids that 2 consecutive measurements of this kind
                                                  //are grouped in the same layer.
                                                  //it would be useful if invalid hit out of the active area were 
                                                  //given the detid reserved for the whole layer instead of 0    
                        ) ;
    
                vector<TM> group(start, ipart);
                result.push_back(pair<const DetLayer*, vector<TM> >(getDetLayer(*start),
                                                        group));
                start = ipart;
        }
#ifdef debug_MeasurementByLayerGrouper_
        //debug
        
        for (vector<pair<const DetLayer*, vector<TM> > >::const_iterator iter = result.begin(); iter != result.end(); iter++){
                LogTrace("MeasurementByLayerGrouper|SiTrackerMultiRecHitUpdator") << "DetLayer " << iter->first << " has " << iter->second.size() << " measurements"; 
        }
#endif
        
        
        //      LogDebug("MeasurementByLayerGrouper|SiTrackerMultiRecHitUpdator") <<"Measurement size "<<result.size();
        return result;
}

const DetLayer* MeasurementByLayerGrouper::getDetLayer(const TM& tm) const {
        // if the DetLayer is set in the TM...  
        if (tm.layer()) return tm.layer();

        //if it corresponds to an invalid hit with no geomdet associated
        //we can't retrieve the  DetLayer
        //because unfortunately the detlayer is not set in these cases
        //returns 0 for the moment
        //to be revisited
        
        if (tm.recHit()->det()==0){
          LogDebug("MeasurementByLayerGrouper") <<"This hit has no geomdet associated skipping... ";
                return 0;
        }

        //now the cases in which the detid is set

        if (!theGeomSearch) {
                throw cms::Exception("MeasurementByLayerGrouper") << "Impossible to retrieve the det layer because it's not set in the TM and the pointer to the GeometricSearchTracker is 0 ";
                return 0;       
        }

        return theGeomSearch->detLayer(tm.recHit()->det()->geographicalId());
}