library: libTreePlayer #include "TTreeIndex.h"

# TTreeIndex

class description - source file - inheritance tree (.pdf)

## class TTreeIndex : public TVirtualIndex

| Inheritance Chart:

`TObject`

<-

`TNamed`

<-

`TVirtualIndex`

<-

`TTreeIndex`

        public:

                                TTreeIndex()
                                TTreeIndex(const TTree* T, const char* majorname, const char* minorname)
                                TTreeIndex(const TTreeIndex&)
                        virtual ~TTreeIndex()
                 static TClass* Class()
                  virtual Int_t GetEntryNumberFriend(const TTree* T)
               virtual Long64_t GetEntryNumberWithBestIndex(Int_t major, Int_t minor) const
               virtual Long64_t GetEntryNumberWithIndex(Int_t major, Int_t minor) const
              virtual Long64_t* GetIndex() const
              virtual Long64_t* GetIndexValues() const
          virtual TTreeFormula* GetMajorFormula()
          virtual TTreeFormula* GetMajorFormulaParent(const TTree* T)
            virtual const char* GetMajorName() const
          virtual TTreeFormula* GetMinorFormula()
          virtual TTreeFormula* GetMinorFormulaParent(const TTree* T)
            virtual const char* GetMinorName() const
               virtual Long64_t GetN() const
                virtual TClass* IsA() const
                    TTreeIndex& operator=(const TTreeIndex&)
                   virtual void Print(Option_t* option = "") const
                   virtual void SetTree(const TTree* T)
                   virtual void ShowMembers(TMemberInspector& insp, char* parent)
                   virtual void Streamer(TBuffer& b)
                           void StreamerNVirtual(TBuffer& b)
                   virtual void UpdateFormulaLeaves()

### Data Members

        protected:

                TString fMajorName           Index major name
                TString fMinorName           Index minor name
               Long64_t fN                   Number of entries
              Long64_t* fIndexValues         [fN] Sorted index values
              Long64_t* fIndex               [fN] Index of sorted values
          TTreeFormula* fMajorFormula        ! Pointer to major TreeFormula
          TTreeFormula* fMinorFormula        ! Pointer to minor TreeFormula
          TTreeFormula* fMajorFormulaParent  ! Pointer to major TreeFormula in Parent tree (if any)
          TTreeFormula* fMinorFormulaParent  ! Pointer to minor TreeFormula in Parent tree (if any)

## Class Description

     A Tree Index with majorname and minorname.

TTreeIndex(): TVirtualIndex()

     Default constructor for TTreeIndex

TTreeIndex(const TTree *T, const char *majorname, const char *minorname) : TVirtualIndex()

     Normal constructor for TTreeIndex

     Build an index table using the leaves of Tree T with  major & minor names
     The index is built with the expressions given in "majorname" and "minorname".

     a Long64_t array fIndexValues is built with:
        major = the value of majorname converted to an integer
        minor = the value of minorname converted to an integer
        fIndexValues[i] = major<<31 + minor
     This array is sorted. The sorted fIndex[i] contains the serial number
     in the Tree corresponding to the pair "major,minor" in fIndexvalues[i].

      Once the index is computed, one can retrieve one entry via
        T->GetEntryWithIndex(majornumber, minornumber)
     Example:
      tree.BuildIndex("Run","Event"); //creates an index using leaves Run and Event
      tree.GetEntryWithIndex(1234,56789); //reads entry corresponding to
                                            Run=1234 and Event=56789

     Note that majorname and minorname may be expressions using original
     Tree variables eg: "run-90000", "event +3*xx". However the result
     must be integer.
     In case an expression is specified, the equivalent expression must be computed
     when calling GetEntryWithIndex.

     To build an index with only majorname, specify minorname="0" (default)

        TreeIndex and Friend Trees
        ---------------------------
     Assuming a parent Tree T and a friend Tree TF, the following cases are supported:
     CASE 1: T->GetEntry(entry) is called
             In this case, the serial number entry is used to retrieve
             the data in both Trees.
     CASE 2: T->GetEntry(entry) is called, TF has a TreeIndex
             the expressions given in major/minorname of TF are used
             to compute the value pair major,minor with the data in T.
             TF->GetEntry(major,minor) is then called (tricky case!)
     CASE 3: T->GetEntry(major,minor) is called.
             It is assumed that both T and TF have a TreeIndex built using
             the same major and minor name.

        Saving the TreeIndex
        --------------------
     Once the index is built, it can be saved with the TTree object
     with tree.Write(); (if the file has been open in "update" mode).

     The most convenient place to create the index is at the end of
     the filling process just before saving the Tree header.
     If a previous index was computed, it is redefined by this new call.

     Note that this function can also be applied to a TChain.

     The return value is the number of entries in the Index (< 0 indicates failure)

     It is possible to play with different TreeIndex in the same Tree.
     see comments in TTree::SetTreeIndex.

~TTreeIndex()

Int_t GetEntryNumberFriend(const TTree *T)

     returns the entry number in this friend Tree corresponding to entry in
     the master Tree T.
     In case this friend Tree and T do not share an index with the same
     major and minor name, the entry serial number in the friend tree
     and in the master Tree are assumed to be the same

Long64_t GetEntryNumberWithBestIndex(Int_t major, Int_t minor) const

     Return entry number corresponding to major and minor number
     Note that this function returns only the entry number, not the data
     To read the data corresponding to an entry number, use TTree::GetEntryWithIndex
     the BuildIndex function has created a table of Double_t* of sorted values
     corresponding to val = major<<31 + minor;
     The function performs binary search in this sorted table.
     If it finds a pair that maches val, it returns directly the
     index in the table.
     If an entry corresponding to major and minor is not found, the function
     returns the index of the major,minor pair immediatly lower than the
     requested value, ie it will return -1 if the pair is lower than
     the first entry in the index.

     See also GetEntryNumberWithIndex

Long64_t GetEntryNumberWithIndex(Int_t major, Int_t minor) const

     Return entry number corresponding to major and minor number
     Note that this function returns only the entry number, not the data
     To read the data corresponding to an entry number, use TTree::GetEntryWithIndex
     the BuildIndex function has created a table of Double_t* of sorted values
     corresponding to val = major<<31 + minor;
     The function performs binary search in this sorted table.
     If it finds a pair that maches val, it returns directly the
     index in the table, otherwise it returns -1.

     See also GetEntryNumberWithBestIndex

TTreeFormula* GetMajorFormula()

     return a pointer to the TreeFormula corresponding to the majorname

TTreeFormula* GetMinorFormula()

     return a pointer to the TreeFormula corresponding to the minorname

TTreeFormula* GetMajorFormulaParent(const TTree *T)

     return a pointer to the TreeFormula corresponding to the majorname in parent tree T

TTreeFormula* GetMinorFormulaParent(const TTree *T)

     return a pointer to the TreeFormula corresponding to the minorname in parent tree T

void Print(Option_t * option) const

     print the table with : serial number, majorname, minorname
     if option = "10" print only the first 10 entries
     if option = "100" print only the first 100 entries
     if option = "1000" print only the first 1000 entries

void Streamer(TBuffer &R__b)

     Stream an object of class TTreeIndex.
     Note that this Streamer should be changed to an automatic Streamer
     once TStreamerInfo supports an index of type Long64_t

void UpdateFormulaLeaves()

     Called by TChain::LoadTree when the parent chain changes it's tree.

void SetTree(const TTree *T)

     this function is called by TChain::LoadTree and TTreePlayer::UpdateFormulaLeaves
     when a new Tree is loaded.
     Because Trees in a TChain may have a different list of leaves, one
     must update the leaves numbers in the TTreeFormula used by the TreeIndex.

### Inline Functions

              Long64_t* GetIndexValues() const
              Long64_t* GetIndex() const
            const char* GetMajorName() const
            const char* GetMinorName() const
               Long64_t GetN() const
                TClass* Class()
                TClass* IsA() const
                   void ShowMembers(TMemberInspector& insp, char* parent)
                   void StreamerNVirtual(TBuffer& b)
             TTreeIndex TTreeIndex(const TTreeIndex&)
            TTreeIndex& operator=(const TTreeIndex&)

Author: Rene Brun 05/07/2004
Last update: root/tree:$Name: $:$Id: TTreeIndex.cxx,v 1.12 2005/06/13 19:19:07 pcanal Exp $
Copyright (C) 1995-2004, Rene Brun and Fons Rademakers. *