Few questions about PROOF

Dear ROOTers,

      first of all let me wish you all the best for the new year!

      I'm writing you because I'm trying to better understand the way PROOF works since it seems to fit all my requirements for parallel event analysis. I'm collaborating in a pretty big standalone ROOT-based code with some tens of classes for data analysis of pixel detectors (sucimaPix<http://groups-beta.google.com/group/sucimaPix-dev>). Even if it is in principle possible to load sucimaPix shared libraries into a ROOT interactive session and run the analysis job from the command line, we prefer to build some executables running in standalone mode. I'm using ROOT 5-15/01 on a linuxx8664 box with gcc 4.1.1. Here come my questions:

• If I got it right, the best way to exploit PROOF is via a TSelector derived class. That's not a problem since my input data are already saved into a TTree, so I just need to produce the skeleton of a TSelector and fill in the empty methods. Then I can successfully run the TSelector from my standalone program adding a line like:

MyTree->Process(MySelector);

In the case I want to run it on PROOF, I added at the beginning a line like this:

TProof::Open("localhost");

(the PROOF server is properly set-up and the two processors of my PC are found)

But, first of all, I wasn't able to compile/link my code using the standard `root-config --cflags --libs` command because it was complaining that the library containing Proof was missing.
Using the trial and error approach, I managed to have it working adding the following libs

-lProof -lThread -lTreePlayer

Is that correct? is there a smarter way? Is it possible to use PROOF from outside an interactive ROOT session? Is it enough to add the TProof::Open() statement to have the Process() worked out by the cluster? or should I do something more?

• I tried to understand how PROOF works and I guessed that each slave has to have its own copy of the input file. Is it right? In the case of a single host cluster with a multiple-processor is it true as well? Is a step-by-step tutorial for PROOF available somewhere?
• In my analysis procedure I have several histograms to be booked and filled. I believe that all these objects must be added to the fOutput list in order to have the different slave contributions merged together at the end. Is it correct? Is it true for all objects having a Merge() method? Should the booking be done in the Begin() or in the SlaveBeginning() method?
• In my original analysis procedure I had a TList containing a set of reference histograms related to the full pixel detector and a certain variable number of other TList containing the same histograms as the main one but concerning only a region of the detector. To solve this problem I created a TList containing TList of histograms. In this way, looping on all the entries of the outer list, I can fill the histos of the sub-region. Is there a way to make it compatible with the PROOF mechanism of the fOutput list? If I add a TList MyList to fOutput, the content of MyList will be merged at the end?

Thank you very much for your precious help!

Best regards,

-- 
Antonio Bulgheroni, PhD
INFN - Sez. Roma III