sPHENIX discussion of software

[Christof E Roland <cer AT mit.edu>]

Hi, 

following our discussion on Tuesday i did a quick study on our storage 
containers, especially the ones using maps, i.e.  the hitsetcontainer.
The hitsetcontainer is the construct storing what is, from the reco software 
point of view, the closest representation of raw data we have defined. 

I filled the hitsetcontainer with either 5 k or ~5.5 million fake hits per 
event and looked at the evolution of the memory footprint of the jobs using 
the prmon tool. From the difference between the low and high occupancy case I 
canlculate the job memory "price tag" of storing a hit, i.e. 3 unint32 - 12 
bytes.

Storing 5 million extra hits in a std map increases the job memory by 0.5GB. 
This corresponds to a ~100byte effective memory price tag including all the 
overhead
and pre allocated memory around stl maps.

Using TObjArrays its about 60 byte

For stl vectors its ~14 which, given the precision with which you can read 
off the GB job memory scale in prmon, is equal to the 12 bytes you expect. 

I guess we should investigate to which extend we can get rid of maps wherever 
we can. 

Cheers

   Christof

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