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 # Notice
 
 **This section of the tutorial is outdated due to switch from `JFactory` to `JOmniFactory`. Refer to a [tutorial on reconstruction algorithms](https://eic.github.io/tutorial-reconstruction-algorithms/) for up-to-date information.**
 
 # Adding a reconstruction algorithm to EICrecon
 
 In JANA, algorithms are kept in `JFactory` classes. These are the classes that
 interact with the JANA framework to match requests for certain objects or
 collections with the algorithm that produces them.
 
 
 ## Creating a new factory
 For this example, we will create a factory that takes reconstructed
 `edm4eic::ProtoCluster` objects from the collection `EcalEndcapNIslandProtoClusters`
 and will create objects of type `edm4eic::Cluster` with collection name
 `EcalEndcapNIslandClusters`.
 
 To start with, create a file in the `EICrecon` source tree called:
 ~~~
 src/detectors/EEMC/Cluster_factory_EcalEndcapNIslandClusters.h
 ~~~
 Edit the file to have these contents:
 
 ```cpp
 #pragma once
 
 #include <cmath>
 
 #include <JANA/JEvent.h>
 #include <JANA/JFactoryT.h>
 #include <edm4eic/ClusterCollection.h>
 #include <edm4eic/ProtoClusterCollection.h>
 
 class Cluster_factory_EcalEndcapNIslandClusters : public JFactoryT<edm4eic::Cluster> {
 public:
     //------------------------------------------
     // Constructor
     Cluster_factory_EcalEndcapNIslandClusters(){
         SetTag("EcalEndcapNIslandClusters");
     }
 
     //------------------------------------------
     // Init
     void Init() override{
         auto m_app = GetApplication();
 
         // This is an example of how to declare a configuration parameter that
         // can be set at run time. e.g. with -PEEMC:EcalEndcapNIslandClusters:scaleFactor=0.97
         m_scaleFactor =0.98;
         m_app->SetDefaultParameter("EEMC:EcalEndcapNIslandClusters:scaleFactor", m_scaleFactor, "Energy scale factor");
     }
 
     //------------------------------------------
     // Process
     void Process(const std::shared_ptr<const JEvent> &event) override{
 
         // Grab inputs
         const auto &protoclusters = *static_cast<const edm4eic::ProtoClusterCollection*>(event->GetCollectionBase("EcalEndcapNIslandProtoClusters"));
 
         // Loop over protoclusters and turn each into a cluster
         std::vector<edm4eic::Cluster*> outputClusters;
         for( auto proto : protoclusters ) {
 
             // Fill cumulative values by looping over all hits in proto cluster
             float energy = 0;
             double energyError_squared = 0.0;
             float time = 1.0E8;
             float timeError;
             edm4hep::Vector3f position;
             double sum_weights = 0.0;
             for( uint32_t ihit=0; ihit<proto.hits_size() ; ihit++){
                 auto const &hit = proto.getHits(ihit);
                 auto weight = proto.getWeights(ihit);
                 energy += hit.getEnergy();
                 energyError_squared += std::pow(hit.getEnergyError(), 2.0);
                 if( hit.getTime() < time ){
                     time = hit.getTime();            // use earliest time
                     timeError = hit.getTimeError();  // use error of earliest time
                 }
                 auto &p = hit.getPosition();
                 position.x += p.x*weight;
                 position.y += p.y*weight;
                 position.z += p.z*weight;
                 sum_weights += weight;
             }
 
             // Normalize position
             position.x /= sum_weights;
             position.y /= sum_weights;
             position.z /= sum_weights;
 
             // Create a cluster object from values accumulated from hits above
             auto cluster = new edm4eic::Cluster(
                 0, // type (?))
                 energy * m_scaleFactor,
                 sqrt(energyError_squared),
                 time,
                 timeError,
                 proto.hits_size(),
                 position,
 
                 // Not sure how to calculate these last few
                 edm4eic::Cov3f(), // positionError,
                 0.0, // intrinsicTheta,
                 0.0, // intrinsicPhi,
                 edm4eic::Cov2f() // intrinsicDirectionError
                 );
 
             outputClusters.push_back( cluster );
         }
 
         // Hand ownership of algorithm objects over to JANA
         Set(outputClusters);
     }
 
 private:
     float m_scaleFactor;
 };
 ```
 
 For the above algorithm to be available in JANA to other factories or plugins,
 you will need to add a `JFactoryGeneratorT` object for it. Do this by editing
 the file named for the source directory in which it resides. In this example,
 because the above file will live in _src/detectors/EEMC_, edit the file
 __src/detectors/EEMC/EEMC.cc_. It should look something like the following where
 the last `include` line and the last _app->Add(...)_ line have been added to
 declare the new factory.
 
 ```cpp
 // Copyright 2022, David Lawrence
 // Subject to the terms in the LICENSE file found in the top-level directory.
 //
 //
 
 #include <JANA/JApplication.h>
 #include <JANA/JFactoryGenerator.h>
 
 
 #include "RawCalorimeterHit_factory_EcalEndcapNRawHits.h"
 #include "CalorimeterHit_factory_EcalEndcapNRecHits.h"
 #include "ProtoCluster_factory_EcalEndcapNTruthProtoClusters.h"
 #include "ProtoCluster_factory_EcalEndcapNIslandProtoClusters.h"
 #include "Cluster_factory_EcalEndcapNClusters.h"
 #include "Cluster_factory_EcalEndcapNMergedClusters.h"
 #include "Cluster_factory_EcalEndcapNIslandClusters.h"
 
 extern "C" {
     void InitPlugin(JApplication *m_app) {
         InitJANAPlugin(m_app);
         m_app->Add(new JFactoryGeneratorT<RawCalorimeterHit_factory_EcalEndcapNRawHits>());
         m_app->Add(new JFactoryGeneratorT<CalorimeterHit_factory_EcalEndcapNRecHits>());
         m_app->Add(new JFactoryGeneratorT<ProtoCluster_factory_EcalEndcapNTruthProtoClusters>());
         m_app->Add(new JFactoryGeneratorT<ProtoCluster_factory_EcalEndcapNIslandProtoClusters>());
         m_app->Add(new JFactoryGeneratorT<Cluster_factory_EcalEndcapNClusters>());
         m_app->Add(new JFactoryGeneratorT<Cluster_factory_EcalEndcapNMergedClusters>());
         m_app->Add(new JFactoryGeneratorT<Cluster_factory_EcalEndcapNIslandClusters>());
     }
 }
 ```
 
 ## Testing the new factory
 
 Add these lines in your plugin:
 
 ```cpp
 // Place this at the top of the processor header file (e.g. DaveTestProcessor.h)
 #include <edm4eic/Cluster.h>
 
 // Place this in the body of the class definition of the processor header file
 TH1D* hRecClusterEnergy = nullptr;
 
 // Place this in the InitWithGlobalRootLock() method in the processor implementation
 // file (e.g. DaveTestProcessor.cc)
 hRecClusterEnergy  = new TH1D("hRecClusterEnergy",  "EcalEndcapNIslandClusters energy (MeV)",  250, 0.0, 400.0);
 
 // Place this in the ProcessSequential method of the same file
 const auto &clusters = *static_cast<const edm4eic::ClusterCollection*>(event->GetCollectionBase("EcalEndcapNIslandClusters"));
 for (auto cluster : clusters) hRecClusterEnergy->Fill(cluster.getEnergy() / dd4hep::MeV);
 ```
 
 Run some events through and have a look at the result. Here is what this looks like
 for the file:
 [https://eicaidata.s3.amazonaws.com/2022-09-04_pgun_e-_podio-0.15_edm4hep-0.6_0-30GeV_alldir_1k.edm4hep.root]()
 
 ![EcalEndcapNIslandClusters energy](EcalEndcapNIslandClusters_energy.png)
 
 ## Generic algorithms
 For EPIC, we have as a goal to use generic algorithms that are framework unaware.
 Thus, for these algorithms the _JFactory_ classes will serve as a layer to JANA
 for these generic algorithm classes.
 
 At this point in time, the generic algorithms that `EICrecon` uses are being kept in the
 `EICrecon` repository. Work is ongoing in a separate repository that is
 planned to host these in the future, but that is being deferred until after the
 initial simulation campaign.
 
 To see an example of how a generic algorithm is being implemented, look at these
 files:
 
 
 [src/detectors/EEMC/RawCalorimeterHit_factory_EcalEndcapNRawHits.h]()<br/>
 [src/algorithms/calorimetry/CalorimeterHitDigi.h]()<br/>
 [src/algorithms/calorimetry/CalorimeterHitDigi.cc]()<br/>
 
 
 Using generic algorithms requires additional classes and so makes things
 slightly more complex. However, the generic algorithms can be recycled
 for use in multiple detector systems which adds some simplification.

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