9.3.3 AssociationVector Container

Complete: 5
Detailed Review status



AssociationVector<KeyRefProd, CVal> stores internally:

  • a container of type V storing the associated quantities. Could be as simple as a std::vector<float>.
  • a reference to a key collection (typically, and edm::RefProd<...>)

The container interface enforces that the stored container (Cval) has the same size as the associated collection (KeyRefProd).

AssociationVector can be used as lighter alternative to AssociationMap<OneToValue<...> > if every object in a collection has an associated quantity that can be stored by value in the association container.

AssociationVector Interface

AssociationVector<KeyRefProd, CVal> assumes there is a collection of objects of type Key already stored in the event, to which a reference object of type KeyRefProd refers to, and stores internally a collection CVal containing the same number of entries as the first collection.

AssociationVector<KeyRefProd, CVal> has an interface very similar to std::vector<std::pair<Key, Val> >, where Val is the object type contained in CVal, Key is a reference to an object in the collection referred to by KeyRefProd.

An example of usage of AssociationVector is the following:

  typedef AssociationVector<MuonRefProd, vector<double> > MuonIsolationCollection;
  Handle<MuonCollection> muons;
  event.getByLabel( "muons", muons );

  // create and fill the association vector
  MuonIsolationCollection isolations( MuonRefProd( muons ) );
  for( size_t i = 0; i < muons->size(); ++ i ) {
    isolations[ i ] = ....;

  // read the association vector
  for( size_t i = 0; i < isolations.size(); ++ i ) {
    MuonIsolationCollection::value_type iso = isolations( i );
    MuonRef mu = iso.first;
    double iso = iso.second;

AssociationVector Interactive Access

Given the simple internal structure of AssociationVector, interactive access is rather simple. The above example, modeling muon isolation, can be plotted against muon momentum as follows:

  Events.Draw( "isolations.data_:globalMuons.pt()" );

Dictionary Generation

AssociationVector<KeyRefProd, CVal> requires the dictionary generation of both:

  • KeyRefProd, and
  • CVal
  • std::pair<Key, Val>

where Key is a reference to an object in the collection referred to by KeyRefProd.

Moreover, the dictionary of the class itself has to be generated declaring the fields transientVector_  and fixed_  (Note: from CMSSW 7 the class template doesn't declare a fixed_ member anymore) as transient data members. Of course, the dictionary of edm::Wrapper<edm::AssociationVector<...> > has to be generated as well.

As example for the type:

  • edm::AssociationVector<edm::RefProd<std::vector<reco::Muon> >, std::vector<float> >"

The following dictionary directives are needed:

  <class name="edm::AssociationVector<edm::RefProd<std::vector<reco::Muon> >,
                   edm::refhelper::FindUsingAdvance<std::vector<reco::Muon> >,
                                     reco::Muon> >,
                                     unsigned int>">
    <field name="transientVector_" transient="true"/>
  <class name="std::pair<edm::Ref<std::vector<reco::Muon>,
                      edm::refhelper::FindUsingAdvance<std::vector<reco::Muon> >,
  <class name="std::vector<std::pair<edm::Ref<std::vector<reco::Muon>,
                      edm::refhelper::FindUsingAdvance<std::vector<reco::Muon> >,
                                            float> >"/>
  <class name="edm::Wrapper<edm::AssociationVector<edm::RefProd<std::vector<reco::Muon> >,
                               edm::refhelper::FindUsingAdvance<std::vector<reco::Muon> >,
                                     reco::Muon> >,
                                     unsigned int> >"/>

Review Status

Editor/Reviewer and date Comments
LucaLista - 26 Apr 2007 Updated to release 1_5_0_pre1
LucaLista - 23 Apr 2007 Page author and page content last edited

Responsible: LucaLista
Last reviewed by: PetarMaksimovic 28 Feb 2008

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Topic revision: r17 - 2018-01-17 - LuigiCalligaris



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