RE: How can I clean the memory used by deleted objects in a TFile/TDirectory?

Hi Pierre-Luc,

The RAM should not grow unless you require it. Note that removing the object from the file does __not__ remove it from memory. To help any further I would need to get a bit more details on what you actually do.

Cheers,
Philippe.

PS. Also why is the code creating thousands of TTrees, this seems unusual.

-----Original Message-----
From: owner-roottalk_at_pcroot.cern.ch [mailto:owner-roottalk_at_pcroot.cern.ch] On Behalf Of Pierre-Luc Drouin
Sent: Friday, April 13, 2007 7:31 PM
To: Philippe Canal; roottalk_at_pcroot.cern.ch Subject: Re: [ROOT] How can I clean the memory used by deleted objects in a TFile/TDirectory?

I have noticed the same problem with RAM memory before I close the TFile. Even if I delete these objects (TH, TTree), the memory used by the process continues to increase. Is it normal too? The code creates many thousands of TTrees and TH objects, so it can fill the whole RAM of the machine quite easily...

Thanks
Pierre-Luc Drouin

Philippe Canal wrote:
> Hi Pierre-Luc,
>
> When you 'delete' an object from a ROOT file, it does not reduce the size
of
> the file. Instead, the add the newly 'freed' file area to a list of
'empty
> space' in the file. This list is first search when writing another object
> to the file to see if one of the space will be able to hold it.
> 'Compacting' the file to remove to empty space would require to shift the
> bit around on the disk (aka an expansive operation). The easiest to
compact
> a ROOT file is simply to create a new file and copy the object to the new
> files. Since you have only histogram and tree, you can use hadd to do
this
> copy.
>
> Cheers,
> Philippe.
>
> -----Original Message-----
> From: owner-roottalk_at_pcroot.cern.ch [mailto:owner-roottalk_at_pcroot.cern.ch]
> On Behalf Of Pierre-Luc Drouin80
> Sent: Thursday, April 12, 2007 11:17 AM
> To: roottalk_at_pcroot.cern.ch
> Subject: [ROOT] How can I clean the memory used by deleted objects in a
> TFile/TDirectory?
>
> Hi,
>
> I have some code that creates and then deletes many objects and (TH,
> TTree, TDirectory) in a ROOT file and that saves this file with only a
> few remaining objects. When I reopen the ROOT file I see only the TKeys
> of the few objects that I have not deleted, but the size of the file is
> way too big for these objects (it looks like that some previously
> deleted objects are still using space) . I would like to know how could
> I clean efficiently the ROOT file. I am using ROOT 5.14/00c. I delete
> the objects in memory using TDirectory::RecursiveRemove(TObject*) and
> the TKeys using TDirectory::Delete(char *).
>
> Thanks
> Pierre-Luc Drouin
>
>
>
Received on Mon Apr 16 2007 - 21:24:39 CEST