Re: Ownership

  > Is there any way for me to know whether the pointer returned to me (by, in this case, createHistogram()) points to an address on the heap?

There are ways, however there are not portable and a bit brittle. More importantly, in this case, you do not need to worry about it. If createHistogram was to return a value that is not 'on the heap' this would be a serious bug in the implementation of createHistogram as this histogram would be gone before you could even use it.

Cheers,
Philippe.

On 10/8/10 5:27 PM, James Patrick Burke wrote:
>
> Hi Rene,
>
> Thank you for your quick reply.
>
> I use h->SetDirectory(0) to remove my histo from gDirectory, which gives me the same result as your suggestion.
>
> (If you have a spare 60 secs, would you mind checking the reasoning in my very short attached macro?)
>
> And, as you say, having removed my histo from gDirectory, it is my responsibility to delete it when I've finished with it.
>
> But just one question:
>
> TH1* h = pdf->createHistogram(hName,*x,Binning(20));
> h->SetDirectory(0);
> delete h;
>
> Is there any way for me to know whether the pointer returned to me (by, in this case, createHistogram()) points to an address on
> the heap? I presumably would not want to call delete if the address is on the stack.
>
> Thanks again,
>
> Jim.
>
>
> root [0] .x jimMacro.C
>
> RooFit v3.12 -- Developed by Wouter Verkerke and David Kirkby
> Copyright (C) 2000-2009 NIKHEF, University of California & Stanford University
> All rights reserved, please read http://roofit.sourceforge.net/license.txt
>
>
> Before h->SetDirectory(0) call:
>
> Address pointed to by h = 0x1897200
> Address pointed to by p = 0x1897200
>
> After h->SetDirectory(0) call:
>
> Address pointed to by h = 0x1897200
> Address pointed to by q = 0
>
> root [1]
>
>
> ---and here's jimMacro.C (also attached):
>
> using namespace RooFit;
>
> void jimMacro()
> {
> // Set up p.d.f.
> TString xName("x");
> RooRealVar *x = new RooRealVar(xName,xName,-3.0,3.0);
> RooRealVar m("m","m",0.0), s("s","s",1.0);
> RooAbsPdf *pdf = new RooGaussian("pdf","pdf",*x,m,s);
>
> // Create histo from p.d.f.
> TString hName("h");
> TH1* h = pdf->createHistogram(hName,*x,Binning(20));
>
> // As I understand it, h is owned by the current directory (gDirectory)
> TString pName(hName); pName += "__"; pName += xName;
> TH1 *p = (TH1*)gDirectory->GetList()->FindObject(pName);
>
> // Check that the object was found
> cout << "\nBefore h->SetDirectory(0) call:\n" << endl;
> cout << "Address pointed to by h = " << h << endl;
> cout << "Address pointed to by p = " << p << endl;
>
> // Remove from directory
> h->SetDirectory(0);
>
> // Should no longer be able to find in gDirectory
> TString qName(pName);
> TH1 *q = (TH1*)gDirectory->GetList()->FindObject(qName);
> cout << "\nAfter h->SetDirectory(0) call:\n" << endl;
> cout << "Address pointed to by h = " << h << endl;
> cout << "Address pointed to by q = " << q << endl << endl;
>
> // It is now my responsibility to delete h when I've finished with it
> delete h; h = NULL; p = NULL;
>
> // Tidy up other stuff
> delete x; x = NULL;
> delete pdf; pdf = NULL;
> }
>
>
> On Fri, 8 Oct 2010, Rene Brun wrote:
>
>> Hi Jim,
>>
>> If you do not understand the Object Ownership chapter (::), I suggest to add
>> TH1::AddDirectory(kFALSE) at the beginning of your script or session.
>> After this call, it is up to you to manage your histograms and delete them when appropriate.
>>
>> Rene Brun
>>
>> On 08/10/2010 07:05, James Patrick Burke wrote:
>>>
>>> ROOT version: 5.26/00
>>> Machine: MacBook (intel), Mac OS X (10.5.8)
>>>
>>> Hello,
>>>
>>> I have, in my code, a function containing the lines:
>>>
>>> TH1* h_data = data_->createHistogram("h_data",*x_,Binning(numBins_));
>>> TH1* h_func = pdf->createHistogram("h_func",*x_,Binning(numBins_));
>>>
>>> (data_ is a RooDataSet*, pdf is a RooGaussian*, x_ is a RooRealVar*).
>>>
>>> If I call this function more than once I get the warning
>>>
>>> Warning in <TROOT::Append>: Replacing existing TH1: h_data__numDegDaysBranch (Potential memory leak).
>>> Warning in <TROOT::Append>: Replacing existing TH1: h_func__numDegDaysBranch (Potential memory leak).
>>>
>>> when running.
>>>
>>> I believe RooAbsReal::createHistogram(...) is the method being called, and from
>>> http://root.cern.ch/root/html/RooAbsReal.html#RooAbsReal:createHistogram%2, I'm told "The caller takes ownership of the returned
>>> histogram".
>>>
>>> Does this mean that I take ownership, or my data_ and pdf objects take ownership?
>>>
>>> Either way, I want to avoid a memory leak and so should presumably call delete somewhere.
>>>
>>> (I'd prefer not to delete data_ and pdf.)
>>>
>>> I've read Chapter 8 (Object Ownership) of the Users Guide, but I'm afraid I don't really follow it :-(
>>>
>>> If somebody could point out how I can avoid this memory leak, I'd be very much obliged.
>>>
>>> (Would simply varying the first argument ("h_data" or "h_func", above) of createHistogram() every time I call my function do the
>>> trick?)
>>>
>>> Sincerely,
>>>
>>> Jim.
>>>
>>>
>>
Received on Sat Oct 09 2010 - 03:28:08 CEST