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Here are some example code snippets showing how to combine drivers to produce a PFA. These are written to be read by people rather than compilers, so they may need extra tweaks to run in practice. If you know of other patterns, or if you see that these examples have become out of date, please update them.

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  • Add, subtract, or clone a named HitMap in the event via a driver:
    • HitMapAddDriver
    • HitMapSubtractDriver
    • HitMapCloneDriver
  • Convert formats (including the previous Map<Long,CalorimeterHit> format for backwards-compatability):
    • HitMapToClusterListDriver
    • HitMapToHitListDriver
    • MapToHitMapDriver
    • HitListToHitMapDriver
    • ClusterListToHitMapDriver
  • Filter the hits in a hitmap:
    • HitMapFilter
    • HitMapFilterDriver

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See TrivialPFA.java in CVS for a worked implementation. TrivialPFA can be accessed from the examples page within JAS, though you will have to compile and load it manually. Here is an even simpler piece of code:

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import org.lcsim.util.hitmap.*;
import org.lcsim.event.*;
import org.lcsim.event.util.*;
import org.lcsim.recon.cluster.cheat.PerfectClusterer;

public class TrivialPFASimplePFA extends Driver
{
  public TrivialPFASimplePFA()
  {
    // Set up a hitmap to hold the raw calorimeter hits in the event
    // This driver reads in a bunch of List<CalorimeterHit> and writes
    // out a HitMap to the event.
    HitMapDriverHitListToHitMapDriver rawHitMap = new HitMapDriverHitListToHitMapDriver();
    rawHitMap.addInputList("EcalBarrHits");
    rawHitMap.addInputList("EcalEndcapHits");
    rawHitMap.addInputList("HcalBarrHits");
    rawHitMap.addInputList("HcalEndcapHits");
    rawHitMap.setOutput("raw hitmap");
    add(rawHitMap);

    // Set up a list of final-state Monte Carlo particles
    // This driver will write out a List<MCParticle> to the event.
    CreateFinalStateMCParticleList mcListMaker = new CreateFinalStateMCParticleList("Gen");
    add(mcListMaker);

    // Cluster the hits (perfect pattern recognition)
    // This driver will reads in the hitmap and the list of MCParticles.
    // It writes out a modified hitmap and a List<Cluster>.
    PerfectClusterer clusterer = new PerfectClusterer();
    clusterer.setInputHitMap("raw hitmap");
    clusterer.setOutputHitMap("leftover hits");
    clusterer.setOutputClusterList("perfect clusters");
    clusterer.setMCParticleList("GenFinalStateParticles");
    add(clusterer);

    // [The rest of the PFA would go here]
  }
}

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Thanks to Guilherme, we have a digitisation simulation package called DigiSim which is available under org.lcsim.digisim. There is an example driver at org.lcsim.plugin.web.examples.DigiSimExample. Borrowing heavily from that, here is an example snippet showing how to use the output from DigiSim:

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public class TrivialPFASimplePFA extends Driver
{
  public TrivialPFASimplePFA()
  {
    // CalHitMapDriver is a driver that produces hitmaps in the format
    // needed by DigiSim:
    add(new org.lcsim.recon.cluster.util.CalHitMapDriver());
    // Run DigiSim, producing raw hit collections:
    org.lcsim.digisim.DigiSimDriver digi = new org.lcsim.digisim.DigiSimDriver();
    add(digi);
    // Convert the output to SimCalorimeterHit format for use in analysis:
    add( new org.lcsim.digisim.SimCalorimeterHitsDriver() );

    // Now we can add some more drivers to analyze the output. For example:

    // Set up a hitmap for the digisim output hits
    HitMapDriverHitListToHitMapDriver digiHitMap = new HitMapDriverHitListToHitMapDriver();
    digiHitMap.addInputList("EcalBarrDigiHits");
    digiHitMap.addInputList("EcalEndcapDigiHits");
    digiHitMap.addInputList("HcalBarrDigiHits");
    digiHitMap.addInputList("HcalEndcapDigiHits");
    digiHitMap.setOutput("digi hitmap");
    add(digiHitMap);

    // Set up the MC list
    CreateFinalStateMCParticleList mcListMaker = new CreateFinalStateMCParticleList("Gen");
    add(mcListMaker);

    // Cluster the hits (perfect pattern recognition)
    PerfectClusterer clusterer = new PerfectClusterer();
    clusterer.setInputHitMap("digi hitmap");
    clusterer.setOutputHitMap("leftover hits");
    clusterer.setOutputClusterList("perfect clusters");
    clusterer.setMCParticleList("GenFinalStateParticles");
    add(clusterer);
  }
}

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import org.lcsim.util.hitmap.HitMapToHitListDriver;

// Here is the PFA class:
public class TrivialPFASimplePFA extends Driver
{
  public TrivialPFASimplePFA()
  {
    // [drivers go here, producing a HitMap called "digi hitmap"]

    // Here's the driver to convert the hitmap into a List<CalorimeterHit> to display:
    HitMapToHitListDriver digiConverterDriver = new HitMapToHitListDriver();
    digiConverterDriver.setInputHitMap("digi hitmap");
    digiConverterDriver.setOutputList("digi hits (displayable)");
    add(digiConverterDriver);

    // [rest of the code goes here]
  }
}

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public class CompletePFA extends Driver
{
  public CompletePFA()
  {
    // First, use DigiSim to make more realistic hits
    add(new org.lcsim.recon.cluster.util.CalHitMapDriver());
    org.lcsim.digisim.DigiSimDriver digi = new org.lcsim.digisim.DigiSimDriver();
    add(digi);
    add( new org.lcsim.digisim.SimCalorimeterHitsDriver() );

    // Produce hitmaps:
    HitMapDriverHitListToHitMapDriver digiHitMap = new HitMapDriverHitListToHitMapDriver();
    digiHitMap.addInputList("EcalBarrDigiHits");
    digiHitMap.addInputList("EcalEndcapDigiHits");
    digiHitMap.addInputList("HcalBarrDigiHits");
    digiHitMap.addInputList("HcalEndcapDigiHits");
    digiHitMap.setOutput("digi hitmap");
    add(digiHitMap);

    // Find tracks with the fast MC (output is a List<Track> saved as EventHeader.TRACKS)
    add (new org.lcsim.mc.fast.tracking.MCFastTracking());

    // Run a MIP-finder, possibly taking the tracks as input.
    // "MipFinder" is a made-up class.
    MipFinder exampleMipFinder = new MipFinder();
    exampleMipFinder.setInputTrackList(EventHeader.TRACKS);
    exampleMipFinder.setInputHitMap("digi hitmap");
    exampleMipFinder.setOutputClusterList("mips");
    exampleMipFinder.setOutputHitMap("digi hitmap after removing mips");
    add(exampleMipFinder);

    // Find E/M clusters
    // "EMFinder" is a made-up class.
    EMFinder exampleEMFinder = new EMFinder();
    exampleEMFinder.setInputHitMap("digi hitmap after removing mips");
    exampleEMFinder.setOutputClusterList("em showers");
    exampleEMFinder.setOutputHitMap("digi hitmap after removing mips and em showers");
    add(exampleEMFinder);

    // Identify the E/M clusters -- photons? electrons? pi0?
    // Output is a List<ReconstructedParticle>.
    // In reality we'd probably iterate a little here on the hit assignments,
    // and might need to pick up MIP segments for a few electrons, but neglect that for now.
    // "EMIdentifier" is a made-up class.
    EMIdentifier exampleEMIdentifier = new EMIdentifier();
    exampleEMIdentifier.setInputClusterList("em showers");
    exampleEMIdentifier.setInputTrackList(EventHeader.TRACKS);
    exampleEMIdentifier.setOutputParticleList("identified em particles");

    // Now find remaining clusters, which should mostly be from hadrons (and muons)
    // after a shower/interaction/scatter. This step is very abstracted and would
    // include all kinds of things such as fragment-handling.
    // "HADClusterer" is a made-up class.
    HADClusterer exampleHADClusterer = new HADClusterer();
    exampleHADClusterer.setInputHitMap("digi hitmap after removing mips and em showers");
    exampleHADClusterer.setInputMipList("mips");
    exampleHADClusterer.setInputTrackList(EventHeader.TRACKS);
    exampleHADClusterer.setOutputHitMap("digi hitmap after removing mips, em showers, and had clusters");
    exampleHADClusterer.setOutputClusterList("had");

    // Identify the hadronic/muon particles found:
    // "HADIdentifier" is a made-up class.
    HADIdentifier exampleEMIdentifier = new EMIdentifier();
    exampleHADIdentifier.setInputClusterList("had");
    exampleHADIdentifier.setInputTrackList(EventHeader.TRACKS);
    exampleHADIdentifier.setOutputParticleList("identified had particles");

    // Then we do something useful with all these ReconstructedParticles.
    // [analysis]
  }
}

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