TTree::Draw and automatic schema evolution

[rsawada]

I would like to ask how can I use automatic schema evolution when I call TTree::Draw in interactive session.

For a test I tried followings.

1. Create a file with a class.

Code: Select all

// myclass.h
#include "TNamed.h"
class myclass: public TNamed
{
 public:
  Double32_t a;
  myclass();
  myclass(const char* name);
  ClassDef(myclass,1);
};

#ifdef __MAKECINT__
#pragma link C++ class myclass+;
#endif

Code: Select all

// myclass.cc

#include "myclass.h"
ClassImp(myclass)
myclass::myclass() {}
myclass::myclass(const char* name){SetName(name);}

Code: Select all

// testclass.cc
#include "myclass.cc"
#include "TFile.h"
#include "TTree.h"
#include "TClonesArray.h"
int main()
{
   TFile f("test.root","recreate");
   TTree *tree = new TTree("tree", "tree");
   TClonesArray *array = new TClonesArray("myclass");
   tree->Branch("a", "TClonesArray", &array, 32000, 99);
   array->ExpandCreate(1);
   ((myclass*) (array->At(0)))->a = 4;
   tree->Fill();
   f.Write();
}

$ rootcint -f dict.cc -c myclass.h+
$ g++ -Wall `root-config --libs --cflags` -o testclass testclass.cc dict.cc
$ ./testclass


2. Change the class structure

Code: Select all

// new myclass.h
#include "TNamed.h"
class myclass: public TNamed
{
 public:
  Double_t a;   // <== changed type
  myclass();
  myclass(const char* name);
  ClassDef(myclass,2); // <== increamented
};

#ifdef __MAKECINT__
#pragma link C++ class myclass+;
#endif

3. Read the file

Code: Select all

$ root
root [0] .L myclass.cc+
root [1] TFile f("test.root")
root [2] tree->Draw("a")

Then what I see in TCanvas is a histgram with an entry at 0 instead of 4.
When I enable debugging messages, it says as following. So ROOT notices the structure has been changed.

Code: Select all

====>Rebuilding TStreamerInfo for class: myclass, version: 1
Creating StreamerInfo for class: myclass, version: 2

StreamerInfo for class: myclass, version=2, checksum=0xd3a58282
  TNamed         BASE            offset=  0 type=67 The basis for a named object (name, title)
  Double_t       a               offset= 28 type= 8                     
   i= 0, TNamed          type= 67, offset=  0, len=1, method=0
   i= 1, a               type=  8, offset= 28, len=1, method=0
Warning in <TStreamerInfo::BuildOld>: element: myclass::Double32_t a has new type: Double_t/8

StreamerInfo for class: myclass, version=1, checksum=0x70d1912d
  TNamed         BASE            offset=  0 type=67 The basis for a named object (name, title)
  Double32_t     a               offset= 28 type= 9                     
   i= 0, TNamed          type= 67, offset=  0, len=1, method=0
   i= 1, a               type=209, offset= 28, len=1, method=0

I am aware that it works when I don't call ".L myclass.cc+", but this is just a sample code to reproduce my problem. What I really do is using the same binary to write and read trees which is linked with my own classes.

with respect

[pcanal]

Hi,

The problem is now corrected in the SVN trunk.

You also have 3 work around:
- compile your script via ACLiC
- use

Code: Select all

myclass * m = ((myclass*) (array->At(0)));
m->a = 4;

- initialize the data member of the class:

Code: Select all

 myclass::myclass() : a(0) {
};

Cheers,
Philippe.

[rsawada]

Thank you for your reply.

I have tried SVN revision 22245, but it does not seem my problem is fixed.
I have also included your second and third suggestions.
I am testing on SL4 on 32 bit i686 CPU.
If you need more information to reproduce the problem, please let me know.


I tried also making an application to read the file.
Procedure 1 and 2 are common with the previous post.

3'-1. Recreate dictionary.
$ rm dict.cc dict.h
$ rootcint -f dict.cc -c myclass.h+

3'-2. Read the file with an application.

Code: Select all

// testclass2.cc
#include "myclass.cc"
#include "TFile.h"
#include "TTree.h"
#include "TPostScript.h"
int main(int argc, char **argv)
{
   TFile f("test.root");
   TTree *tree = (TTree*)f.FindObjectAny("tree");
   TPostScript ps("test.ps");
   tree->Draw("a.a");
}

g++ -Wall `root-config --libs --cflags` -o testclass2 testclass2.cc dict.cc
./testclass2
gv test.ps


Ryu

[pcanal]

Hi,

With the fix, I can not longer reproduce this problem. Note that the problem is while _writing_ the file (i.e. you need to rewrite it before the problem goes away).
To help in reproducing the problem that you still have, please upload a tar file with all the files (and makefile if any) that you use (and instructions)

Cheers,
Philippe.

[rsawada]

Hi.

Thank you for your help.

I attached a tar.gz file. It includes a makefile so that you can do the same procedure by just typing 'make'.

[pcanal]

Hi,

Thanks for this complete example . I can now reproduce the problem (which in the TTreeFormula mechanism and should be fixed shortly).

You can work around the problem by introducing a getter member function (GetA() for example) and using it to plot the values (tree->Draw("mybranch.GetA());

Cheers,
Philippe.

[pcanal]

Hi,

The problem is now fixed in the SVN trunk.

Thanks for your report.

Philippe

[rsawada]

Hi.

Now SVN trunk is fine.

Thank you for your help.

Ryu