TTree->GetEntry with a TTReeIndex is too slow

[feliciasutanto]

Dear All,

It seems that reading TTree not sequentially (i.e., using TTreeIndex) leads to decompression issue…
This post solves the slow TTree random access problem:

Randomized access in a tree

Ahaaaaa!! Now I see my memory usage skyrocket to 1.6GBytes (the actual file size)! I bet my code will run faster now – I’ll check and let you know in 10min. So what was the difference? Rather than do LoadBaskets() on ptree, I did it on the actual branch – is that it? And, to answer your questions, here’s the output: root [4] cout << b->GetListOfBaskets()->GetEntries() << '\n'; 479 root [5] gROOT->ProcessLine("ptree->Dump(); > ptree.dump"); root [6] gROOT->ProcessLine(".! grep TotalBuffer…

Cheers,
Felicia