Re: Saving/Retrieving vector, map in root file

Hi Amnon,

My solution did not force a change in the Tree structure, only new objects in the UserInfo list.
I think that the solution depends a lot on the way(s) you want to use the filtering information.
My suggestion was to add standard classes, much more efficient (time and space) than the C++ map.

You can also imagine another possibility, using for example a TH1I having as many bins as you have entries in your tree. You can use up to 32 bits (1 bit/cut/entry) with the advantage that you can use the standard bool operations (masks, etc) to test a combination of bits. Then store the TH1I in the UserInfo or as a normal TKey.

Rene

Amnon Harel wrote:
>
> Hi Rene,
>
> Can you please comment on the efficiency of the follow solution,
> which I normally use and would've recommended to Hovhannes?
>
> Since you're already filling in information, why not add
> pass/fail fields to the tree, one for each cut?
>
> This has the advantage that you can then easily combine cuts
> using the usual ROOT tools. It should be efficient on disk
> and in I/O since ROOT compresses each leaf separately,
> so will use only a bit for each pass/fail entry.
>
> At least, that's what I thought until I saw Rene's answer :-)
>
> cheers,
> Amnon
>
>
>
> -----Original Message-----
> From: owner-roottalk_at_root.cern.ch on behalf of Rene Brun
> Sent: Tue 05-Oct-10 6:57 AM
> To: Hovhannes Khandanyan
> Cc: roottalk (Mailing list discussing all aspects of the ROOT system.)
> Subject: Re: [ROOT] Saving/Retrieving vector, map in root file
>
> Hi Hovhannes,
>
> Instead of the expensive/inefficient C++ map, I recommend one of the 2
> following solutions
> -Solution 1: Create a TBits object + a TObjString. You mark the
> TBits(i) for the entries passing (or not) your cut and in the TObjString
> you give a name to your cut. If you have many cuts, you can group your
> TBits in a TObjArray mybits and same for the TObjString mycuts. At the
> end of your job, add your 2 TObjArrays to mytree.GetUserInfo()
> mytree->GetUserInfo()->Add(mybits)
> mytree->GetUserInfo()->Add(mycuts)
>
> -Solution 2: Create one TEntryList for each cut (a TEntryList uses
> internally TBits for passing (or not) cuts
> and add yout TEntryList to mytree.GetUserInfo().
>
> Generally speaking you can add as many objects (meta data, etc) to the
> GetUserInfo list. This has the advantage
> to keep a close contact between your Tree and the associated meta data.
>
> Rene Brun
>
>
>
> Khandanyan wrote:
> >
> > Dear ROOTers,
> >
> > I am running my analysis over N events applying m cuts in my event
> > selection. While running over events I fill TTree leaves per parameter
> > of interest for the analysis (Pt, Met etc.) Each leaf hence has N
> > entries. Along with this I define a C++ map associating cut name with
> > the number of events that passed given cut (hence map of size m). So
> > what would be the best way to store this map, so that I can later on
> > retrieve it for further analysis?
> >
> > Thank you,
> > Hovhannes
>
>
Received on Tue Oct 05 2010 - 15:27:09 CEST