Re: MakeClass()

Hi Monika,

In your PMD.C file, you should have a statement:

   Long64_t nentries = fChain->GetEntriesFast(); In case of a TChain, nentries will be the large number 1234567890. At this point, ROOT does not know the total number of entries in all files. This is to avoid opening each file twice. When executing the loop, the loop will terminate correctly when all events will be processed.
You can also replace GetEntriesFast by GetEntries. It will return the right number of entries
but it will be slower.

Rene Brun

Monika Sharma wrote:
>
> Hi Rene,
>
> Thank you for quick answer. I tried it but I am facing a strange
> problem.
>
> Following is what I did recently :
> void Pmd_cucu_analysis()
> {
>
> TChain chain("PmdNano");
> chain.Add("PMD_Nanodst_feb4_540Kevts.root");
> chain.Add("PMD_Nanodst_feb4_540Kevts_1.root");
> chain.MakeClass("PMD");
>
> }
>
> It does generate PMD.C and PMD.h. However when I try to read the
> number of events in PMD.C, it gives me a very large number of events.
> Which are not actually present intotality in the above two mentioned
> rootfiles.
>
> For example :
> Following is the output I get when I execute PMD.C
> root.exe [1] .L PMD.C
> root.exe [2] PMD t
> root.exe [3] t.Loop()
> Total events = 1234567890
> Warning in <TClass::TClass>: no dictionary for class PmdEvent is
> available
> Warning in <TClass::TClass>: no dictionary for class PmdCluster is
> available
> Warning in <TClass::TClass>: no dictionary for class PmdHit is available
> Warning in <TClass::TClass>: no dictionary for class PmdTrack is
> available
> root.exe [4] .q
>
> But when I try to see the number of events indiviually from the
> rootfiles,
> this is what I get :
>
>
> root.exe [0]
> Attaching file PMD_Nanodst_feb4_540Kevts.root as _file0...
> Warning in <TClass::TClass>: no dictionary for class PmdEvent is
> available
> Warning in <TClass::TClass>: no dictionary for class PmdCluster is
> available
> Warning in <TClass::TClass>: no dictionary for class PmdHit is available
> Warning in <TClass::TClass>: no dictionary for class PmdTrack is
> available
> root.exe [1] PmdNano->GetEntries()
> (const Long64_t)367860
> root.exe [2] .q
>
> And :
> root.exe [0]
> Attaching file PMD_Nanodst_feb4_540Kevts_1.root as _file0...
> Warning in <TClass::TClass>: no dictionary for class PmdEvent is
> available
> Warning in <TClass::TClass>: no dictionary for class PmdCluster is
> available
> Warning in <TClass::TClass>: no dictionary for class PmdHit is available
> Warning in <TClass::TClass>: no dictionary for class PmdTrack is
> available
> root.exe [1] PmdNano->GetEntries()
> (const Long64_t)406344
> root.exe [2] .q
>
> So I expect a total of 774204 events from PMD.C (Because this is the
> actual number
> of events present in the rootfiles). Is there any obvious mistake
> that I am making.
>
> Thanks in advance.
> Regards
> Monika
>
>
> Rene Brun wrote:
>
>> Hi Monika,
>>
>> You should use a TChain to process a collection of files
>>
>> TChain chain("VW");
>> chain.Add("filename_*.root");
>> chain.MakeClass("something");
>>
>> Rene Brun
>>
>> Monika Sharma wrote:
>>
>>>
>>> Hi Rooters,
>>>
>>> I am trying to use MakeClass function to read a .root file.
>>> Following is a typical example of what I am doing :
>>>
>>> ========================================
>>> void analysis()
>>> {
>>>
>>> TFile *f = new TFile("Event_transport.root");
>>> TTree *v = (TTree*)f->Get("VW");
>>> f->ls();
>>>
>>> v->MakeClass("something");
>>> }
>>> =========================================
>>>
>>> This generates a .C and a .h file, which works fine for me.
>>> But now my aim is to increase statistics. Therefore I have two
>>> rootfiles
>>> each of ~2 GB size, as a result I cannot merge them any further.
>>>
>>> I wanted to ask is there anyway that I can still use MakeClass function
>>> to read these rootfiles together which would generate one .C and .h
>>> file
>>> so that I have double the statistics.
>>>
>>> I tried doing
>>> =============================================
>>> void analysis()
>>> {
>>>
>>> for(Int_t nFiles=0; nFiles<2; nFiles++)
>>> {
>>> char fname[150];
>>> sprintf(fname,"filename_%d.root",nFiles);
>>> cout<<endl;
>>> printf(fname,"filename_%d.root",nFiles);
>>> TFile *file = new TFile(fname,"r");
>>> TTree *P = (TTree*)file->Get("VW");
>>> file->ls();
>>> }
>>> P->MakeClass("something");
>>> }
>>> =====================================================
>>>
>>> But the above method generates .C and .h files taking the last
>>> rootfile as
>>> the input.
>>>
>>> Thanks in advance.
>>> Monika
>>
Received on Tue Feb 06 2007 - 08:27:16 CET