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Usage of FairLink [message #14639] Fri, 19 April 2013 13:15 Go to next message
Volker Friese is currently offline  Volker Friese
Messages: 365
Registered: April 2004
Location: GSI CBM
first-grade participant
From: *gsi.de
In the process of using the FairLink scheme, I came across several questions and was unable to find some documentation, so I post them here:

1. FairLink has several constructors. The basic difference is whether the object to be linked to is specified by branch name (TString) or type (Int_t). Is there some recommendation which one to use?

2. FairMultiLinkedData::AddLink (FairLink link, Bool_t bypass=kFALSE, Float_t mult=1.0): What is the meaning of bypass and mult?


Thanks in advance,

Volker
Re: Usage of FairLink [message #14640 is a reply to message #14639] Fri, 19 April 2013 13:59 Go to previous message
Tobias Stockmanns is currently offline  Tobias Stockmanns
Messages: 489
Registered: May 2007
first-grade participant
From: 195.37.186*
Dear Volker,

here are the answers to your questions:

1) The type inside the link is used to identify the branch inside a Tree where the data is stored.
The FairRootManager crates a unique ID for each branch which is stored in the FairLink. The constructor using a TString gets the branch name and translates it via the FairRootManager into the type while the constructor with an Int_t type gets this unique ID directly.

2 a) The bypass parameter allows to suppress links to intermediate steps which are not of interest. If one adds a link to FairMultiLinkedData with bypass = true then the links are stored where the given link is pointing to and not the link by itself.

2 b) The mult. parameter is used to create a weight if you use the links to retrieve MC data. For example if you want to know the MC track for a reconstructed track it might be, that the reconstructed track is merged from data of different MC tracks. Therefore you do not get a single MC track as a result but many. The weight parameter helps to sort the results by their significants.
As a user who is setting the links the parameter should be always 1.

I hope I could answer your questions.

Cheers,

Tobias
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