Hi Karl,
Interesting observation.
I have optimized this case in the current version in CVS.
It would be nice if you could try this version to see the effect
in your case.
Let me know
Rene Brun
K. Hauschild wrote:
>
> Hi All,
>
> I want to make my root Data files smaller : here is what I do, but I would like
> to know if the is a more space efficient way of storing the data.
>
> I have the following class to store/access data for a particular detector type.
>
> //Class for CsI Detectors
> class DetectorCsI : public TObject {
>
> private:
> UShort_t fId; //Detector Id
> UShort_t fPId; //Detector Particle Id
> UShort_t fChan; //Detector chan
> UShort_t fTac; //Detector TAC
>
> public:
> DetectorCsI() {;}
> DetectorCsI(UShort_t id, UShort_t pid, UShort_t chan, UShort_t tac);
> virtual ~DetectorCsI() {;}
>
> //setters and getters
> inline UShort_t GetId() {return fId; }
> inline UShort_t GetPId() {return fPId; }
> inline UShort_t GetChan() {return fChan;}
> inline UShort_t GetTac() {return fTac; }
>
> ClassDef (DetectorCsI,1) //CsI Detector class
> };
>
> In an event there are a variable number of CsI detectors hit, so I
> use TClonesArrays, eg :
>
> OrsayData::OrsayData()
> {
> // Create a Data object for the Orsay experiment
> //class static variable are 0 for first time call
> if (fgGes == 0)
> fgGes = new TClonesArray("DetectorGe", N_GE); //Ge/BGO data array
>
> if (fgSaphir == 0)
> fgSaphir = new TClonesArray("Detector", N_SAPHIR); //array for Saphir
>
> if (fgCsIs == 0)
> fgCsIs = new TClonesArray("DetectorCsI",N_DIAMANT);//array for CsI
>
> fGes = fgGes;
> fSaphir = fgSaphir;
> fCsIs = fgCsIs;
>
> fSumBus1 = fSumBus2 = 0;
> fNGe = fNCsI = fNSaphir = 0;
> }
>
> (I have similar TClonesArrays for the Ge/BGO and Saphir data.)
>
> The event saved to a tree is given by :
>
> ///////////////////////////////////////////////////////////////////////////////
> // Class to store/extract processed data
> //
> class OrsayData : public TObject{
> private:
> UChar_t fSumBus1; //Saphir Trigger
> UChar_t fSumBus2; //Ge/BGO Trigger
>
> int fNGe; //! HPGe multiplicity : this info is stored in
> int fNBGO; //! BGO multiplicity : the TClonesArray below
> int fNCsI; //! CsI multiplicity : so not wirtten to file
> int fNSaphir; //! Saphir multiplicity
>
> TClonesArray *fGes; // Ge Data
> TClonesArray *fSaphir; // Saphir Data
> TClonesArray *fCsIs; // CsI Data
>
> static TClonesArray *fgGes; // these are used for
> static TClonesArray *fgSaphir; // of TClonesArray
> static TClonesArray *fgCsIs; // of TClonesArray
>
> public:
> OrsayData();
> virtual ~OrsayData();
>
> void Clear(Option_t *option = "");
> static void Reset(Option_t *option = "");
>
> //setters
> void SetSumBus1(int SumBus1) {fSumBus1 = SumBus1;}
> void SetSumBus2(int SumBus2) {fSumBus2 = SumBus2;}
>
> void AddGe( UShort_t id, UShort_t chan, UShort_t tac,
> UShort_t bgo_chan, UShort_t bgo_tac);
> void AddSaphir( UShort_t id, UShort_t chan, UShort_t tac);
> void AddCsI( UShort_t id, UShort_t chan, UShort_t tac, UShort_t pid);
>
> //getters : processed data
> inline int GetSumBus1() { return fSumBus1; }
> inline int GetSumBus2() { return fSumBus2; }
> inline int GetNGe() { return fNGe; }
> inline int GetNBGO() { return fNBGO; }
> inline int GetNCsI() { return fNCsI; }
> inline int GetNSaphir() { return fNSaphir; }
>
> TClonesArray *GetGes() const {return fGes;}
> TClonesArray *GetSaphir() const {return fSaphir;}
> TClonesArray *GetCsIs() const {return fCsIs;}
>
> ClassDef (OrsayData,1) //Orsay Data class
> };
>
>
> Using ->Print() on my TTree I have :
>
> *Br 10 :fCsIs : fCsIs_ *
> *Entries : 48523408 : Total Size= 388477911 bytes File Size = 113153367 *
> *Baskets : 4551 : Basket Size= 128000 bytes Compression= 3.43 *
> *............................................................................*
> *Br 11 :fCsIs.fId : fId[fCsIs_] *
> *Entries : 48523408 : Total Size= 205360612 bytes File Size = 17502009 *
> *Baskets : 3120 : Basket Size= 128000 bytes Compression= 11.73 *
> *............................................................................*
> *Br 12 :fCsIs.fPId : fPId[fCsIs_] *
> *Entries : 48523408 : Total Size= 205360396 bytes File Size = 20880526 *
> *Baskets : 3120 : Basket Size= 128000 bytes Compression= 9.84 *
> *............................................................................*
> *Br 13 :fCsIs.fChan : fChan[fCsIs_] *
> *Entries : 48523408 : Total Size= 205363516 bytes File Size = 21180885 *
> *Baskets : 3120 : Basket Size= 128000 bytes Compression= 9.70 *
> *............................................................................*
> *Br 14 :fCsIs.fTac : fTac[fCsIs_] *
> *Entries : 48523408 : Total Size= 205360396 bytes File Size = 20198629 *
> *Baskets : 3120 : Basket Size= 128000 bytes Compression= 10.17 *
> *............................................................................*
>
> So, in this case "fCsIs_" is a large overhead. I presume this is where
> the number of CsI elements hit is stored per event entry. From the numbers
> above it would seem this is 8 bytes per event entry. In my particular
> case this need only be 8 bits since I have less than 255 CsI detectors.
> Why is the overhead needed by ROOT so large ?. Is there any way to define
> the size of "fCsIs_" ?
>
> Or, am I barking up the wrong tree and there is a more space
> efficient way of handling this ?
>
> Many thanks,
>
> Karl
>
> ==========================================================================
>
> CEA Saclay, DAPNIA/SPhN Phone : (33) 01 69 08 7553
> Bat 703 - l'Orme des Merisiers Fax : (33) 01 69 08 7584
> F-91191 Gif-sur-Yvette E-mail : khauschild@cea.fr
> France karl_hauschild@yahoo.co.uk
> WWW: http://www-dapnia.cea.fr/Sphn
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