TChain::GetEntries returns 1234567890

ROOT
1

I need to add about 40 some odd files into a TChain (read-only), the total number of events should be about 2.5 billion. However, somehow function GetEntries always return 1234567890. The following is the documentation on this function:

Long64_t GetEntries() const

Return the total number of entries in the chain. In case the
number of entries in each tree is not yet known, the offset table
is computed.

Since I am only reading the files, the number of entries should be known already, right? Any suggestion as how I would figure out exactly how many entries are there?

Thanks

John

2

When you call TChain::Add, instead of
mychain.Add(filename);
do
mychain.Add(filename,0);

Rene