need to speedup/refactor EgammaHcalIsolation

[slava77]

This is a follow-up to some initial work done already in #35955

a better refactoring of the code should be considered in near future. Some options are

• accumulate all needed isolation types in one loop over rechits
  • compute multiple cone isolation in a single loop over rechits, e.g. 0.3 and 0.4
• precompute (η,φ) of rechits in a separate producer in a ValueMap and use it when dR computations are needed
  • this will eliminate the calls to calo geometry geometry and the cost of recomputing (η,φ) from (x,y,z)
    @wrtabb @SohamBhattacharya

Gains expected

• around 0.5-0.7% in full reco
• larger gains may be present in HLT or analysis setups

[cmsbuild]

A new Issue was created by @slava77 Slava Krutelyov.

@Dr15Jones, @perrotta, @dpiparo, @makortel, @smuzaffar, @qliphy can you please review it and eventually sign/assign? Thanks.

cms-bot commands are listed here

[slava77]

assign reconstruction,@cms-sw/egamma-pog-l2

[makortel]

assign reconstruction, egamma-pog

[cmsbuild]

New categories assigned: reconstruction,egamma-pog

@slava77,@jpata,@lfinco,@swagata87 you have been requested to review this Pull request/Issue and eventually sign? Thanks

[swagata87]

just to keep track,
this was another improvement along this direction (thanks to Slava)
#36108

[jpata]

type performance-improvements

[jpata]

@wrtabb @SohamBhattacharya please take note of this opportunity for performance improvements. We should start to prioritize computing improvements.

@cms-sw/egamma-pog-l2

[jpata]

type egamma