I’ve done a test adding two files a.root and b.root, each 2.2G. I compare the times to add them using hadd in root versions 5.24, 5.22, and 5.20 below, all 64-bit.
time hadd aplusb.root a.root b.root
Version 5.24 (64 bit)
real 29m16.634s
user 3m13.032s
sys 25m22.793s
Version 5.22 (64 bit)
real 1m50.372s
user 0m2.465s
sys 0m19.955s
Version 5.20 (64 bit)
real 1m3.823s
user 0m2.417s
sys 0m17.864s
Original post below:
Hello,
Is anyone familiar with hadd? I’ve been using it to merge files (TTree files, not just histograms) and it has worked very well. I recently moved to root version v5.24(64bit) and notice hadd takes much longer to complete than it used to in v5.18(32bit).
As a demonstration, I have 3 ntuples, fileA.root,fileB.root, and fileC.root. Each file is 1.2G.
When I do:
time hadd outfile.root fileA.root fileB.root fileC.root
these are the times I get:
ROOT v5.24 (64 bit)
real 22m18.719s
user 1m15.661s
sys 17m28.543s
ROOT v5.18 (32 bit)
real 0m48.092s
user 0m2.817s
sys 0m17.018s
22 minutes vs 48 seconds . . . ??? Any help is much appreciated.
Cheers,
Sean