nsmith- / aioroot

Adventures in asynchronous programming

aioroot

An asynchronous library for reading ROOT files over xrootd.

This package is an investigation into using asynchronous programming via async/await syntax in python 3 to make remote reading of ROOT files as concurrent as possible. The package takes a lot of inspiration from uproot.

The initial goal is to provide an equivalent to the uproot.numentries function, which is optimized to extract the number of entries in a given TTree embedded in a ROOT file as quickly as possible. In both implementations, the typical file requires 3 synchronous xrootd read() calls, however in this library we: trigger the sequence of calls concurrently for all files to be read; do any decompression in a thread pool outside the loop, and never block on read IO so the main thread can continue unpacking the structures. The net effect is an on average 5x speedup for a list of 10 files as shown in demo.py. Running this demo at home (in the US):

$ ./demo.py
Elapsed (async): 3.28 s
Elapsed (uproot): 24.47 s
All entries agree? True

and running it on a CERN lxplus machine (very close to the file servers):

$ ./demo.py
Elapsed (async): 0.05 s
Elapsed (uproot): 0.24 s
All entries agree? True

In preparing this implementation, the structure unpacking functions had to be largely reworked from uproot, as there the unpacking and IO are heavily intertwined. I think the sans-io philosophy may apply also to this case, and uproot could easily become both a sync/async library if the structure unpacking is separated from IO fully.