class TTreeCache: public TFileCacheRead


A specialized TFileCacheRead object for a TTree
This class acts as a file cache, registering automatically the
baskets from the branches being processed (TTree::Draw or
TTree::Process and TSelectors) when in the learning phase.
The learning phase is by default 100 entries.
It can be changed via TTreeCache::SetLearnEntries.

This cache speeds-up considerably the performance, in particular
when the Tree is accessed remotely via a high latency network.

The default cache size (10 Mbytes) may be changed via the function

Only the baskets for the requested entry range are put in the cache

For each Tree being processed a TTreeCache object is created.
This object is automatically deleted when the Tree is deleted or
when the file is deleted.

-Special case of a TChain
Once the training is done on the first Tree, the list of branches
in the cache is kept for the following files.

-Special case of a TEventlist
if the Tree or TChain has a TEventlist, only the buffers
referenced by the list are put in the cache.

Function Members (Methods)

TTreeCache(TTree* tree, Int_t buffersize = 0)
voidTObject::AbstractMethod(const char* method) const
voidAddBranch(TBranch* b, Bool_t subbranches = kFALSE)
voidAddBranch(const char* branch, Bool_t subbranches = kFALSE)
virtual voidTObject::AppendPad(Option_t* option = "")
virtual voidTObject::Browse(TBrowser* b)
static TClass*Class()
virtual const char*TObject::ClassName() const
virtual voidTObject::Clear(Option_t* = "")
virtual TObject*TObject::Clone(const char* newname = "") const
virtual Int_tTObject::Compare(const TObject* obj) const
virtual voidTObject::Copy(TObject& object) const
virtual voidTObject::Delete(Option_t* option = "")
virtual Int_tTObject::DistancetoPrimitive(Int_t px, Int_t py)
virtual voidTObject::Draw(Option_t* option = "")
virtual voidTObject::DrawClass() const
virtual TObject*TObject::DrawClone(Option_t* option = "") const
virtual voidTObject::Dump() const
virtual voidTObject::Error(const char* method, const char* msgfmt) const
virtual voidTObject::Execute(const char* method, const char* params, Int_t* error = 0)
virtual voidTObject::Execute(TMethod* method, TObjArray* params, Int_t* error = 0)
virtual voidTObject::ExecuteEvent(Int_t event, Int_t px, Int_t py)
virtual voidTObject::Fatal(const char* method, const char* msgfmt) const
virtual TObject*TObject::FindObject(const char* name) const
virtual TObject*TObject::FindObject(const TObject* obj) const
virtual Int_tTFileCacheRead::GetBufferSize() const
virtual Option_t*TObject::GetDrawOption() const
static Long_tTObject::GetDtorOnly()
virtual const char*TObject::GetIconName() const
static Int_tGetLearnEntries()
virtual const char*TObject::GetName() const
virtual char*TObject::GetObjectInfo(Int_t px, Int_t py) const
static Bool_tTObject::GetObjectStat()
virtual Option_t*TObject::GetOption() const
TTree*GetOwner() const
virtual const char*TObject::GetTitle() const
TTree*GetTree() const
virtual UInt_tTObject::GetUniqueID() const
virtual Bool_tTObject::HandleTimer(TTimer* timer)
virtual ULong_tTObject::Hash() const
virtual voidTObject::Info(const char* method, const char* msgfmt) const
virtual Bool_tTObject::InheritsFrom(const char* classname) const
virtual Bool_tTObject::InheritsFrom(const TClass* cl) const
virtual voidTObject::Inspect() const
voidTObject::InvertBit(UInt_t f)
virtual TClass*IsA() const
virtual Bool_tTFileCacheRead::IsAsyncReading() const
virtual Bool_tTObject::IsEqual(const TObject* obj) const
virtual Bool_tTObject::IsFolder() const
Bool_tIsLearning() const
Bool_tTObject::IsOnHeap() const
virtual Bool_tTObject::IsSortable() const
Bool_tTObject::IsZombie() const
virtual voidTObject::ls(Option_t* option = "") const
voidTObject::MayNotUse(const char* method) const
virtual Bool_tTObject::Notify()
static voidTObject::operator delete(void* ptr)
static voidTObject::operator delete(void* ptr, void* vp)
static voidTObject::operator delete[](void* ptr)
static voidTObject::operator delete[](void* ptr, void* vp)
void*TObject::operator new(size_t sz)
void*TObject::operator new(size_t sz, void* vp)
void*TObject::operator new[](size_t sz)
void*TObject::operator new[](size_t sz, void* vp)
virtual voidTObject::Paint(Option_t* option = "")
virtual voidTObject::Pop()
virtual voidTFileCacheRead::Prefetch(Long64_t pos, Int_t len)
virtual voidTFileCacheRead::Print(Option_t* option = "") const
virtual Int_tTObject::Read(const char* name)
virtual Int_tReadBuffer(char* buf, Long64_t pos, Int_t len)
virtual voidTObject::RecursiveRemove(TObject* obj)
voidTObject::ResetBit(UInt_t f)
virtual voidTObject::SaveAs(const char* filename = "", Option_t* option = "") const
virtual voidTObject::SavePrimitive(basic_ostream<char,char_traits<char> >& out, Option_t* option = "")
voidTObject::SetBit(UInt_t f)
voidTObject::SetBit(UInt_t f, Bool_t set)
virtual voidTObject::SetDrawOption(Option_t* option = "")
static voidTObject::SetDtorOnly(void* obj)
voidSetEntryRange(Long64_t emin, Long64_t emax)
virtual voidTFileCacheRead::SetFile(TFile* file)
static voidSetLearnEntries(Int_t n = 100)
static voidTObject::SetObjectStat(Bool_t stat)
virtual voidTObject::SetUniqueID(UInt_t uid)
virtual voidShowMembers(TMemberInspector& insp, char* parent)
virtual voidTFileCacheRead::Sort()
virtual voidStreamer(TBuffer& b)
voidStreamerNVirtual(TBuffer& b)
virtual voidTObject::SysError(const char* method, const char* msgfmt) const
Bool_tTObject::TestBit(UInt_t f) const
Int_tTObject::TestBits(UInt_t f) const
voidUpdateBranches(TTree* tree, Bool_t owner = kFALSE)
virtual voidTObject::UseCurrentStyle()
virtual voidTObject::Warning(const char* method, const char* msgfmt) const
virtual Int_tTObject::Write(const char* name = 0, Int_t option = 0, Int_t bufsize = 0)
virtual Int_tTObject::Write(const char* name = 0, Int_t option = 0, Int_t bufsize = 0) const
virtual voidTObject::DoError(int level, const char* location, const char* fmt, va_list va) const
TTreeCache(const TTreeCache&)
TTreeCache&operator=(const TTreeCache&)

Data Members

enum TObject::EStatusBits { kCanDelete
enum TObject::[unnamed] { kIsOnHeap
TList*fBrNames! list of branch names in the cache
TObjArray*fBranches! List of branches to be stored in the cache
char*TFileCacheRead::fBuffer[fBufferSize] buffer of contiguous prefetched blocks
Int_tTFileCacheRead::fBufferLenCurrent buffer length (<= fBufferSize)
Int_tTFileCacheRead::fBufferSizeAllocated size of fBuffer (at a given time)
Int_tTFileCacheRead::fBufferSizeMinOriginal size of fBuffer
Int_tTFileCacheRead::fBytesToPrefetchHelpers to allow the incremental async prefetch
Long64_tfEntryMax! last entry in the cache
Long64_tfEntryMin! first entry in the cache
Long64_tfEntryNext! next entry number where cache must be filled
TFile*TFileCacheRead::fFilePointer to file
Bool_tfIsLearning! true if cache is in learning mode
Bool_tfIsManual! true if cache is StopLearningPhase was used
Bool_tTFileCacheRead::fIsSortedTrue if fSeek array is sorted
Int_t*TFileCacheRead::fLen[fNb] Length of long buffers
Int_tfNReadMissNumber of blocks read and not found in the chache
Int_tfNReadOkNumber of blocks read and found in the cache
Int_tfNReadPrefNumber of blocks that were prefetched
Int_tTFileCacheRead::fNbNumber of long buffers
Int_tfNbranches! Number of branches in the cache
Int_tTFileCacheRead::fNseekNumber of blocks to be prefetched
Int_tTFileCacheRead::fNtotTotal size of prefetched blocks
TTree*fOwner! pointer to the owner Tree/chain
Long64_t*TFileCacheRead::fPos[fNb] start of long buffers
Long64_t*TFileCacheRead::fSeek[fNseek] Position on file of buffers to be prefetched
Long64_t*TFileCacheRead::fSeekIndex[fNseek] sorted index table of fSeek
Int_t*TFileCacheRead::fSeekLen[fNseek] Length of buffers to be prefetched
Int_t*TFileCacheRead::fSeekPos[fNseek] Position of sorted blocks in fBuffer
Int_tTFileCacheRead::fSeekSizeAllocated size of fSeek
Long64_t*TFileCacheRead::fSeekSort[fNseek] Position on file of buffers to be prefetched (sorted)
Int_t*TFileCacheRead::fSeekSortLen[fNseek] Length of buffers to be prefetched (sorted)
TTree*fTree! pointer to the current Tree
Long64_tfZipBytes! Total compressed size of branches in cache
static Int_tfgLearnEntriesNumber of entries used for learning mode

Class Charts

Inheritance Inherited Members Includes Libraries
Class Charts

Function documentation

TTreeCache(const TTreeCache& )
 Default Constructor.
TTreeCache(TTree* tree, Int_t buffersize = 0)
 destructor. (in general called by the TFile destructor
void AddBranch(TBranch *b, Bool_t subbranches /*= kFALSE*/)
add a branch to the list of branches to be stored in the cache
this function is called by TBranch::GetBasket
void AddBranch(const char *bname, Bool_t subbranches /*= kFALSE*/)
 Add a branch to the list of branches to be stored in the cache
 this is to be used by user (thats why we pass the name of the branch).
 It works in exactly the same way as TTree::SetBranchStatus so you
 probably want to look over ther for details about the use of bname
 with regular expresions.
 The branches are taken with respect to the Owner of this TTreeCache
 (i.e. the original Tree)
Bool_t FillBuffer()
 Fill the cache buffer with the branches in the cache.
Double_t GetEfficiency()
 Give the total efficiency of the cache... defined as the ratio
 of blocks found in the cache vs. the number of blocks prefetched
 ( it could be more than 1 if we read the same block from the cache more
   than once )
 Note: This should eb used at the end of the processing or we will
       get uncomplete stats
Double_t GetEfficiencyRel()
 This will indicate a sort of relative efficiency... a ratio of the
 reads found in the cache to the number of reads so far
Int_t GetLearnEntries()
static function returning the number of entries used to train the cache
see SetLearnEntries
TTree * GetOwner()
return the owner of this cache.
TTree * GetTree()
return Tree in the cache
Int_t ReadBuffer(char* buf, Long64_t pos, Int_t len)
 Read buffer at position pos.
 If pos is in the list of prefetched blocks read from fBuffer.
 Otherwise try to fill the cache from the list of selected branches,
 and recheck if pos is now in the list.
    -1 in case of read failure,
     0 in case not in cache,
     1 in case read from cache.
 This function overloads TFileCacheRead::ReadBuffer.
void SetEntryRange(Long64_t emin, Long64_t emax)
 Set the minimum and maximum entry number to be processed
 this information helps to optimize the number of baskets to read
 when prefetching the branch buffers.
void SetLearnEntries(Int_t n = 100)
 Static function to set the number of entries to be used in learning mode
 The default value for n is 10. n must be >= 1
void StartLearningPhase()
 The name should be enough to explain the method.
 The only additional comments is that the cache is cleaned before
 the new learning phase.
void StopLearningPhase()
 This is the counterpart of StartLearningPhase() and can be used to stop
 the learning phase. It's useful when the user knows exactly what branches
 he is going to use.
 For the moment it's just a call to FillBuffer() since that method
 will create the buffer lists from the specified branches.
void UpdateBranches(TTree* tree, Bool_t owner = kFALSE)
update pointer to current Tree and recompute pointers to the branches in the cache
TTreeCache(const TTreeCache& )
TTreeCache& operator=(const TTreeCache& )
Bool_t IsLearning()
{return fIsLearning;}

Author: Rene Brun 04/06/2006
Last update: root/tree:$Id: TTreeCache.h 20882 2007-11-19 11:31:26Z rdm $
Copyright (C) 1995-2000, Rene Brun and Fons Rademakers. *

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