Pythia8pp stack out of stored

When using pythia8pp in simulations, I’m see information messages about stack at each start of event:

Event 9
$$$X Primary track 100
[10:28:27][INFO] This event/chunk did 5774 steps
[10:28:27][INFO] Longest track time is 1.5441e-06
[10:28:27][INFO] Stack: 715 out of 913 stored

I’m using the following commans: o2-sim -m MFT -e TGeant4 -n 10 -g pythia8pp --seed 0 --timestamp 1 --field 5

Do you know what is the meaning of these messages?

Hi. These messages summarize the number of MC steps done for each sub-event (group of particles tracked). For the particle stack, it tells the number of MC tracks persisted in the kinematics output, in comparison to how many were transported. Note that we only store tracks which satisfy hits and other physics criteria.

But you can ask to keep all MC tracks by using --configKeyValues "Stack.pruneKine=false".

Thanks a lot Sandro.