My PC has 4 processors - how do I use them all?

ROOT
1

Hi all,

I use root to read in a large number of particle physics events, apply a load of cuts and then draw some histograms. I do this using the MakeClass method and then putting my cuts inside the Loop() method. I prefer to complie my program rather than run things in cint.

I work on a pc with 4 processors and would like to 1/4 my running time by sharing the load. To start with I would be happy to get 2 processors going. How do I go about doing this? I have looked at PROOF documentation but figure it out.

Can anyone tell me how to do a MakeClass sytle Loop() over all my events but using multiple processors?

Thanks in advance
John

2

Yes. The solution is to use PROOF. For the user code instead of MakeClass you need to use MakeSelector (you can compile the code of course :slight_smile: ).

Philippe

3

Is there any chance you could post a simple program that will do a “Loop()” over a set of events in the TSelector, multi processor way?

It’s always easier to copy/follow an example than spend hours hacking around with the code and lost in the documentation.

:smiley:

4

See gks05.fzk.de/upload/Exercises/exercises.html for example.
Essentially the only difference with using a TSelector (see the User’s Guide) is to call the proper TProof::Connect.

Cheers,
Philippe