Event Reconstruction Database : a lesson in pragmatic design
The ASCII file generated from the Monte Carlo contains text numbers representing tracker and E.M calorimeter information
ASCII data is ~250 kBytes per event
Each simulated event in the file has
- ~2500 “hits” (x,y,z,dx,dy,dz)
- ~300 crystals with energy
After converting these data to (binary) objects they are inserted in the Objectivity database. They take ~1 Mbyte per event
Reconstructing the tracks and energy clusters (~3 minutes per event), yields ~50 tracks, and ~20 clusters.
The reconstructed data adds ~1 Mbyte per event (now we have ~2 Mbyte in total!)
This indicates that great care must be taken in deciding which objects to make persistent in the ODBMS.
- Store the hits as a single object that is an ordered array