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Fri Aug 19 19:27:05 2011 UTC (3 years, 5 months ago) by
pcanal
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From Bruno Lenzi: TEntryListArray
TEntryListArray is an extension of TEntryList, used to hold selected entries and subentries (sublists) of a TTree. It is useful in case of a TTree with containers (vectors, arrays, ...). A typical example is the case when each entry of a TTree corresponds to physics events and each subentry (index of arrays) represents a particle.
Its main purpose is to improve the performance of a code that needs to apply complex selections (cuts) on TTree::Draw multiple times. Evaluating such cuts can be time consuming for large trees due to the need for loading the associated information (branches). This operation is done once with the use of a TEntryListArray. Subsequent calls to TTree::Draw only need to load the requested branches for histogramming, while using only the entries and subentries that satisfied the previous selection.
TTree/TSelectorDraw: use of TEntryListArray to select entries and subentries. If the option "entrylistarray" is specified, a TEntryListArray is created and filled with the entries and subentries that pass the given selection. If TTree::Draw is called after a TEntryList is set, only the selected entries and subentries are used to fill histograms or create new entrylists.
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