undo TrackExtra size increase done in #17367

[slava77]

this was done to get 900pre3 going and gives about 10% increase in RECO size.
Follow up will need to have some changes in fastsim first.

@VinInn @ssekmen

[cmsbuild]

A new Issue was created by @slava77 Slava Krutelyov.

@davidlange6, @Dr15Jones, @smuzaffar can you please review it and eventually sign/assign? Thanks.

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[slava77]

@VinInn @ssekmen @mdhildreth
Are we in position now to advance with this issue?

Recall that the RECO data tier was increased by 10% due to issues in FastSim with PU (#17367)

[smuzaffar]

@slava77 , any update on this?

[slava77]

adding TRK conveners
@mtosi @JanFSchulte

[slava77]

assign reconstruction,simulation

[cmsbuild]

New categories assigned: reconstruction,simulation

@mdhildreth,@slava77,@perrotta,@civanch you have been requested to review this Pull request/Issue and eventually sign? Thanks

[slava77]

(to refresh the status) this is still active in a way; there was a recent discussion in connection with #30544 (which remained as an RFC and closed; a more generic variant of #31217, which was merged).

@cms-sw/fastsim-l2

the point here is to make the following data members transient (again)

   TrajParams=vector<LocalTrajectoryParameters> m_trajParams;
   Chi2sFive=vector<uchar> m_chi2sX5;  // chi2 * 5  chopped at 255

To quote a few pieces from the email thread in August 2020 (after we narrowed down that the only use case is apparently in FastTrackDeDxProducer):
@slava77 :

My somewhat simplistic understanding of the fastsim use case is that
FastTrackDeDxProducer can use propagated ~expected trajectory parameters
instead of the actual local trajectory parameters from the fit.

@VinInn :

In very good approximation yes (One can even refit the track starting from the hit (this is done for some DQM module)...):
I agree.
Not "Fast" though....

[slava77]

assign fastsim

[cmsbuild]

New categories assigned: fastsim

@mdhildreth,@sbein,@ssekmen,@lveldere,@civanch you have been requested to review this Pull request/Issue and eventually sign? Thanks

[slava77]

@cms-sw/fastsim-l2
was there a follow up to this?

Please clarify.
Thank you.

[jpata]

@cms-sw/fastsim-l2 any update here?

[smuzaffar]

@cms-sw/fastsim-l2 any update?