Dear ROOT experts,
I have the following ROOT file forum.root (792.7 KB) which contains a TTree with the following structure:
root [1] EventTree->Print()
******************************************************************************
*Tree :EventTree : Event Tree *
*Entries : 1000 : Total = 2431957 bytes File Size = 790896 *
* : : Tree compression factor = 3.07 *
******************************************************************************
*Branch :fEvent *
*Entries : 1000 : BranchElement (see below) *
*............................................................................*
*Br 0 :fEventID : Int_t *
*Entries : 1000 : Total Size= 4581 bytes File Size = 1523 *
*Baskets : 1 : Basket Size= 32000 bytes Compression= 2.68 *
*............................................................................*
*Br 1 :fSubEventID : Int_t *
*Entries : 1000 : Total Size= 4596 bytes File Size = 133 *
*Baskets : 1 : Basket Size= 32000 bytes Compression= 30.70 *
*............................................................................*
*Br 2 :fInfo : TString *
*Entries : 1000 : Total Size= 5574 bytes File Size = 1544 *
*Baskets : 1 : Basket Size= 32000 bytes Compression= 3.29 *
*............................................................................*
*Br 3 :fTracks : Int_t fTracks_ *
*Entries : 1000 : Total Size= 17178 bytes File Size = 2662 *
*Baskets : 1 : Basket Size= 32000 bytes Compression= 3.04 *
*............................................................................*
*Br 4 :fTracks.fTrackID : Int_t fTrackID[fTracks_] *
*Entries : 1000 : Total Size= 48273 bytes File Size = 6261 *
*Baskets : 2 : Basket Size= 32000 bytes Compression= 7.61 *
*............................................................................*
*Br 5 :fTracks.fParentID : Int_t fParentID[fTracks_] *
*Entries : 1000 : Total Size= 48279 bytes File Size = 6057 *
*Baskets : 2 : Basket Size= 32000 bytes Compression= 7.87 *
*............................................................................*
*Br 6 :fTracks.fSteps.fStepID : vector<int> fStepID[fTracks_] *
*Entries : 1000 : Total Size= 117531 bytes File Size = 14736 *
*Baskets : 4 : Basket Size= 32000 bytes Compression= 7.93 *
*............................................................................*
*Br 7 :fTracks.fSteps.fPosition : vector<TVector3> fPosition[fTracks_] *
*Entries : 1000 : Total Size= 686967 bytes File Size = 337256 *
*Baskets : 22 : Basket Size= 32000 bytes Compression= 2.03 *
*............................................................................*
*Br 8 :fTracks.fSteps.fMomentum : vector<TVector3> fMomentum[fTracks_] *
*Entries : 1000 : Total Size= 686967 bytes File Size = 200968 *
*Baskets : 22 : Basket Size= 32000 bytes Compression= 3.41 *
*............................................................................*
*Br 9 :fTracks.fSteps.fTimeGlobal : vector<double> fTimeGlobal[fTracks_] *
*Entries : 1000 : Total Size= 180807 bytes File Size = 133531 *
*Baskets : 6 : Basket Size= 32000 bytes Compression= 1.35 *
*............................................................................*
*Br 10 :fTracks.fSteps.fSensitive : vector<bool> fSensitive[fTracks_] *
*Entries : 1000 : Total Size= 70176 bytes File Size = 12017 *
*Baskets : 3 : Basket Size= 32000 bytes Compression= 5.79 *
*............................................................................*
*Br 11 :fTracks.fSteps.fVolumeName : vector<TString> fVolumeName[fTracks_] *
*Entries : 1000 : Total Size= 217773 bytes File Size = 17121 *
*Baskets : 7 : Basket Size= 32000 bytes Compression= 12.68 *
*............................................................................*
*Br 12 :fTracks.fSteps.fVolumeNameTransportationFrom : *
* | vector<TString> fVolumeNameTransportationFrom[fTracks_] *
*Entries : 1000 : Total Size= 70309 bytes File Size = 12090 *
*Baskets : 3 : Basket Size= 32000 bytes Compression= 5.76 *
*............................................................................*
*Br 13 :fTracks.fSteps.fProcessName : *
* | vector<TString> fProcessName[fTracks_] *
*Entries : 1000 : Total Size= 140066 bytes File Size = 17974 *
*Baskets : 5 : Basket Size= 32000 bytes Compression= 7.76 *
*............................................................................*
*Br 14 :fTracks.fSteps.fProcessType : *
* | vector<TString> fProcessType[fTracks_] *
*Entries : 1000 : Total Size= 70190 bytes File Size = 12025 *
*Baskets : 3 : Basket Size= 32000 bytes Compression= 5.78 *
*............................................................................*
*Br 15 :fTracks.fSteps.fProcessSubType : *
* | vector<TString> fProcessSubType[fTracks_] *
*Entries : 1000 : Total Size= 70211 bytes File Size = 12041 *
*Baskets : 3 : Basket Size= 32000 bytes Compression= 5.78 *
*............................................................................*
root [2]
As you can see the file contains some TString to store information for things such as process names, volume name etc. (instead of using an integer ID since ROOT will compress the file I think this is a good decision, but please comment on this if you can).
I am having some problems with the TString though. The file seems to be OK but I cannot find a consistent way to visualize the contents of the file using the Tree Viewer (EventTree->StartViewer()) or the TBrowser. Maybe its not worth it to work with strings in ROOT but most likely I am doing something wrong.
If I open the file with ROOT 6.22/08 compiled with C++11
I can see the string values, but the number of entries is not correct. It shows 10867 which should be 15758. 10867 corresponds to the first entry of fTracks.fSteps.fVolumeName, which is a std::vector. If you plot any other member such as SizeOf you get the correct value:
Ploting the same via the tree viewer I get the same incorrect result:
Also, if I do all this via my other ROOT installation compiled with C++17 (version 6.24/02) I get the same result for the tree viewer, but I cannot display the strings in the TBrowser, I get the following:
